Glycogen Storage Disease

**167**

**Chapter 10**

*Georg Bollig*

**Abstract**

provided.

sports medicine

**1.1 No sports?**

**1. Introduction and background**

those who have to live with McArdle disease.

Sports and McArdle Disease

Danger or Therapy?

(Glycogen Storage Disease Type V):

McArdle disease (glycogen storage disease type V) is an inborn error of energy metabolism in the muscle. The effects of McArdle disease on physical performance have similarities with the metabolic state of marathon runners after glycogen depletion and can therefore be seen as a nature's experiment in the field of sports medicine. Many patients with McArdle disease avoid sports in general because physical activity usually leads to muscle pain and muscle cramps. Often patients therefore regard physical activity as both painful and possibly dangerous. This chapter is about the advantages and possible risks of sports for patients with McArdle disease. The scientific literature will be discussed highlighting both endurance and muscle strength exercise. It will discuss the differences of aerobic and anaerobic exercise in individuals suffering from McArdle disease. Complications as rhabdomyolysis, myoglobinuria, kidney failure, and malignant hyperthermia will be discussed. The chapter will summarize the current knowledge about the possible dangers versus possible benefits of sports for patients with McArdle disease. A summary of recommendations for physical exercise and training for McArdle patients will be

**Keywords:** McArdle disease, glycogen storage disease type V, rhabdomyolysis, endurance exercise, muscle strength exercise, aerobic exercise, anaerobic exercise,

Many people with McArdle disease do not like sports or physical activity and say therefore no to participation in sports activities or regular physical exercise. The aim of this chapter is to address patients and health care providers' queries about vMcArdle disease and sports as well as to provide guidance on physical activity for

McArdle disease (glycogen storage disease type V) is an inborn error of energy metabolism in the muscle [1–5]. It hampers physical exercise in affected patients due to the restriction of the availability of glucose as energy source for muscular work. It can be seen as a nature's experiment in the field of sports medicine as the underlying defect of the myophosphorylase enzyme leads to metabolic effects

#### **Chapter 10**

## Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy?

*Georg Bollig*

#### **Abstract**

McArdle disease (glycogen storage disease type V) is an inborn error of energy metabolism in the muscle. The effects of McArdle disease on physical performance have similarities with the metabolic state of marathon runners after glycogen depletion and can therefore be seen as a nature's experiment in the field of sports medicine. Many patients with McArdle disease avoid sports in general because physical activity usually leads to muscle pain and muscle cramps. Often patients therefore regard physical activity as both painful and possibly dangerous. This chapter is about the advantages and possible risks of sports for patients with McArdle disease. The scientific literature will be discussed highlighting both endurance and muscle strength exercise. It will discuss the differences of aerobic and anaerobic exercise in individuals suffering from McArdle disease. Complications as rhabdomyolysis, myoglobinuria, kidney failure, and malignant hyperthermia will be discussed. The chapter will summarize the current knowledge about the possible dangers versus possible benefits of sports for patients with McArdle disease. A summary of recommendations for physical exercise and training for McArdle patients will be provided.

**Keywords:** McArdle disease, glycogen storage disease type V, rhabdomyolysis, endurance exercise, muscle strength exercise, aerobic exercise, anaerobic exercise, sports medicine

#### **1. Introduction and background**

#### **1.1 No sports?**

Many people with McArdle disease do not like sports or physical activity and say therefore no to participation in sports activities or regular physical exercise. The aim of this chapter is to address patients and health care providers' queries about vMcArdle disease and sports as well as to provide guidance on physical activity for those who have to live with McArdle disease.

McArdle disease (glycogen storage disease type V) is an inborn error of energy metabolism in the muscle [1–5]. It hampers physical exercise in affected patients due to the restriction of the availability of glucose as energy source for muscular work. It can be seen as a nature's experiment in the field of sports medicine as the underlying defect of the myophosphorylase enzyme leads to metabolic effects

that are similar to the effects of glycogen depletion in marathon runners [2]. Many patients with McArdle disease (McAd) avoid sports because physical activity usually leads to muscle pain and muscle cramps. Often patients with McAd therefore regard physical activity as both painful and dangerous. On the other hand, physical activity is of great importance to manage daily life. Living is based on regular motion, and muscles have to be used in order to be healthy. Not using our muscles will in the long run lead to weakness, immobility, and frailty. Therefore people affected by McArdle disease do benefit of keeping a certain degree of fitness. Regular physical exercise might play a key role in delaying progressive muscle wasting, weakness, and frailty in later life of people affected by McAd.


These and many other questions arise when talking about physical activity and sports with patients with McAd. People with McAd do therefore need guidance on physical activity based on scientific and evidence-based facts. Due to unpleasant experience with sports in the form of pain, cramps, weakness, or myoglobinuria, many patients with McAd show a tendency to avoid sports and physical activity because they are afraid that sports may be not only painful but also harmful. Unfortunately this behavior can decrease their physical activity and physical capacity further. This chapter will shed light on McArdle disease and sports in general and try to answer the above mentioned questions.

#### **2. Method**

This chapter is based on a review of the existing publications on McArdle disease (glycogenosis type V) and sports and the authors' personal experience with the topic based on his German PhD thesis on the subject [2] and practical experience with patients with McArdle disease from sports medicine and anesthesiology. A literature search with the Medical Subject Heading (MeSH) words "McArdle disease" and "sports" was performed using the search engines PubMed and Medline. Publications that had McArdle disease and sports as a topic were included. In addition reference lists of books and other sources were assessed by hand search. An overview of the existing literature on this topic is provided.

#### **3. McArdle disease: a nature's experiment**

McArdle disease was first described in 1951 by Brian McArdle, a British neurologist. It is known by different synonyms as myophosphorylase insufficiency, glycogen storage disease type V, or myophosphorylase deficiency [1–5]. **Table 1** provides an overview of the different types of glycogen storage diseases [6]. McArdle disease is caused by a lack of myophosphorylase (alpha-1,4-glucan orthophosphate glycosyl transferase) that normally initiates muscle glycogen breakdown during exercise by removing 1,4-glycosyl groups from the glycogen molecule leading to the release of glucose-1-phosphate [1–5] and thus providing fuel for muscular work. Patients with McAd are unable to use the glycogen storage in the muscles as an energy source to enable physical activity.

In about 50% of patients with McAd, a positive family history can be found. For most of the patients, the diagnosis is first established between the age of 10 and 30 [3]. The disease is described to be autosomal recessive, although transmission

**169**

named R50X [5].

**Table 1.**

100,000 [8].

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy?*

**Enzyme defect Inheritance Organs** 

Autosomal recessive

recessive

Autosomal recessive

Autosomal recessive

Autosomal recessive

Autosomal recessive

Autosomal recessive

X-linked recessive

X-linked recessive

Autosomal recessive

**involved**

Liver, kidney

Muscle, heart, liver

Liver, muscle, heart

Liver, kidney, heart, muscle

Skeletal muscle

Skeletal muscle

Liver, brain

Liver, muscle **Clinical symptoms**

Growth retardation, hypoglycemia

Hypotonia, muscle weakness (progressive), affected: proximal and respiratory muscle, cardiac enlargement and

Growth retardation, muscle weakness (liver cirrhosis can occur)

Mild hypoglycemia

Exercise intolerance, muscle cramps and pain, myoglobinuria on strenuous exercise

Muscle pain and fatigue on exercise. Muscle cramps and tenderness

Ataxia, spasms, brain degeneration

Exercise intolerance, muscle pain

Liver Fasting hypoglycemia, tiredness, pallor, vomiting, muscle cramps

failure

Liver Mild hypoglycemia

Liver Mild hypoglycemia

clinically appears to be autosomal dominant in some affected families [2–4, 7]. The gene for myophosphorylase lies on chromosome 11q13. There are a number of different mutations described in the scientific literature; the most frequent mutation is

The prevalence of McArdle disease is not known exactly due to the relative benign course of the disease and the often mild and frequently misinterpreted clinical symptoms. The clinical symptoms are summarized in **Table 2**. Haller has estimated the prevalence of McArdle disease in the Dallas-Fort Worth region as 1 in

As the pathophysiological effects of McAd are similar to the state of glycogen depletion in marathon runners, it is of special interest from the view of sports

medicine and has been called a nature experiment [2].

*DOI: http://dx.doi.org/10.5772/intechopen.89204*

Glucose-6-phosphatase

Debrancher enzyme deficiency

Branching enzyme deficiency

Myophosphorylase deficiency

Liver phosphorylase deficiency

Phosphofructokinase

deficiency

Type VIII Phosphorylase b kinase deficiency

Type IX Phosphoglycerate kinase deficiency

Type X Phosphoglycerate mutase deficiency

*Overview of glycogen storage diseases (modified from [6]).*

Acid maltase deficiency Autosomal

deficiency

Type 0 Glycogen synthase deficiency

**Type of glycogen storage disease**

Type I **Von Gierke disease**

Type II **Pompe disease**

Type III **Cori disease**

Type IV **Andersen disease**

Type V **McArdle disease**

Type VI **Hers disease**

Type VII **Tarui disease**


*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy? DOI: http://dx.doi.org/10.5772/intechopen.89204*

#### **Table 1.**

*Cellular Metabolism and Related Disorders*

that are similar to the effects of glycogen depletion in marathon runners [2]. Many patients with McArdle disease (McAd) avoid sports because physical activity usually leads to muscle pain and muscle cramps. Often patients with McAd therefore regard physical activity as both painful and dangerous. On the other hand, physical activity is of great importance to manage daily life. Living is based on regular motion, and muscles have to be used in order to be healthy. Not using our muscles will in the long run lead to weakness, immobility, and frailty. Therefore people affected by McArdle disease do benefit of keeping a certain degree of fitness. Regular physical exercise might play a key role in delaying progressive muscle wast-

• But how much physical activity is beneficial and what might be dangerous?

These and many other questions arise when talking about physical activity and sports with patients with McAd. People with McAd do therefore need guidance on physical activity based on scientific and evidence-based facts. Due to unpleasant experience with sports in the form of pain, cramps, weakness, or myoglobinuria, many patients with McAd show a tendency to avoid sports and physical activity because they are afraid that sports may be not only painful but also harmful. Unfortunately this behavior can decrease their physical activity and physical capacity further. This chapter will shed light on McArdle disease and sports in general

This chapter is based on a review of the existing publications on McArdle disease

McArdle disease was first described in 1951 by Brian McArdle, a British neurologist. It is known by different synonyms as myophosphorylase insufficiency, glycogen storage disease type V, or myophosphorylase deficiency [1–5]. **Table 1** provides an overview of the different types of glycogen storage diseases [6]. McArdle disease is caused by a lack of myophosphorylase (alpha-1,4-glucan orthophosphate glycosyl transferase) that normally initiates muscle glycogen breakdown during exercise by removing 1,4-glycosyl groups from the glycogen molecule leading to the release of glucose-1-phosphate [1–5] and thus providing fuel for muscular work. Patients with McAd are unable to use the glycogen storage in the muscles as an energy source to enable physical activity.

In about 50% of patients with McAd, a positive family history can be found. For most of the patients, the diagnosis is first established between the age of 10 and 30 [3]. The disease is described to be autosomal recessive, although transmission

(glycogenosis type V) and sports and the authors' personal experience with the topic based on his German PhD thesis on the subject [2] and practical experience with patients with McArdle disease from sports medicine and anesthesiology. A literature search with the Medical Subject Heading (MeSH) words "McArdle disease" and "sports" was performed using the search engines PubMed and Medline. Publications that had McArdle disease and sports as a topic were included. In addition reference lists of books and other sources were assessed by hand search. An

ing, weakness, and frailty in later life of people affected by McAd.

• Are certain types of physical exercise better than others?

and try to answer the above mentioned questions.

overview of the existing literature on this topic is provided.

**3. McArdle disease: a nature's experiment**

**168**

**2. Method**

*Overview of glycogen storage diseases (modified from [6]).*

clinically appears to be autosomal dominant in some affected families [2–4, 7]. The gene for myophosphorylase lies on chromosome 11q13. There are a number of different mutations described in the scientific literature; the most frequent mutation is named R50X [5].

The prevalence of McArdle disease is not known exactly due to the relative benign course of the disease and the often mild and frequently misinterpreted clinical symptoms. The clinical symptoms are summarized in **Table 2**. Haller has estimated the prevalence of McArdle disease in the Dallas-Fort Worth region as 1 in 100,000 [8].

As the pathophysiological effects of McAd are similar to the state of glycogen depletion in marathon runners, it is of special interest from the view of sports medicine and has been called a nature experiment [2].


**Table 2.**

*Clinical symptoms and signs of McArdle disease [1–4].*

#### **4. Typical clinical picture and diagnosis of McArdle disease**

#### **4.1 Typical clinical picture**

Typical clinical symptoms of McArdle disease are muscle pain and fatigue during exercise. Pain is often located in the knee, calf, and legs. Normally pain vanishes after a few minutes rest. Clinical symptoms and signs are shown in **Table 2** [1–4].

#### **4.2 Diagnosis of McArdle disease**

Diagnosis is based on the clinical picture, muscle biopsy, biochemical tests, exercise testing, and genetic testing [2–4, 7, 9] as listed in **Table 3**.

The absence of rising lactate is a diagnostic criterion in McAd. Usually this has been tested using the forearm ischemic exercise test [2–4]. Both Bollig [2] and Vissing and Haller [9] have suggested to use cycle ergometry testing instead of the forearm ischemic exercise test. The ischemic forearm exercise is more painful for the patients and might put them at risk for severe rhabdomyolysis and myoglobinuria. The cycle ergometry as diagnostic tool from sports medicine is useful in the diagnosis of McAd and may be used to assess the actual state of cardiopulmonary fitness and may help to give patients guidance for further training. **Figure 1** shows the results of cycle ergometry testing in a typical patient with McArdle disease [2].


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*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy?*

The prognosis of McArdle disease is usually good, and life expectancy is normal

At present there are no causal treatment options available. Some symptomatic treatment options may reduce symptoms or enhance the amount physical activity that can be tolerated. These treatment options include oral sucrose before exercise [11], a low dose of oral creatine [12], vitamin B6 [2, 10], and coenzyme Q10 [2, 10]. Our study about the use of clenbuterol over a 12-month period leads to a subjective improvement of exercise tolerance in three patients. Some relatives of the patients noted an improved exercise tolerance after clenbuterol intake over some weeks [2]. One patient from our study has used a low-dose clenbuterol (0.005–0.02 mg once daily) to enhance exercise tolerance for more than 10 years. This patient used clenbuterol for some months with regular breaks of weeks up to months between the therapy cycles. A systematic Cochrane review on pharmacological and nutritional treatment options has been published by Quinlivian et al. [12]. There do exist animal models for McArdle disease in sheep, cows, mice, and rats that may be used to test potential therapies in future studies [10]. Gene therapy of McArdle disease might be a future option, but its dangers outweigh the possible advantages at present [10].

**6. Health problems and possible risks associated with McArdle disease**

kidney failure due to rhabdomyolysis after exercise or anesthesia [2, 3, 12, 13]. Therefore, patients affected by McAd should learn how to accomplish daily activity

Patients with McArdle disease are at risk of developing myoglobinuria and even

although severe cases with muscle wasting and extreme weakness and death in

*DOI: http://dx.doi.org/10.5772/intechopen.89204*

childhood have been described [1–4, 10].

*Cycle ergometry of patient F.M., born 1967, 183 cm, 80 kg; modified from [2].*

**5. Treatment options**

**Figure 1.**

#### **Table 3.** *Diagnosis of McArdle disease [2–4, 7, 9, 10].*

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy? DOI: http://dx.doi.org/10.5772/intechopen.89204*


**Figure 1.** *Cycle ergometry of patient F.M., born 1967, 183 cm, 80 kg; modified from [2].*

The prognosis of McArdle disease is usually good, and life expectancy is normal although severe cases with muscle wasting and extreme weakness and death in childhood have been described [1–4, 10].

#### **5. Treatment options**

*Cellular Metabolism and Related Disorders*

• Muscle pain (myalgia)

• Exercise intolerance • Intermittent claudication

• Second wind phenomenon

• Muscle swelling after exercise

• Fatigue • Cramps

• Stiffness

**Table 2.**

• Myoglobinuria • Muscular atrophy

**4.1 Typical clinical picture**

**4.2 Diagnosis of McArdle disease**

**4. Typical clinical picture and diagnosis of McArdle disease**

• (Exercise becomes easier after a period of moderate and tolerable exercise)

• (Mostly proximal muscles affected and in elderly patients)

*Clinical symptoms and signs of McArdle disease [1–4].*

exercise testing, and genetic testing [2–4, 7, 9] as listed in **Table 3**.

Typical clinical symptoms of McArdle disease are muscle pain and fatigue during exercise. Pain is often located in the knee, calf, and legs. Normally pain vanishes after a few minutes rest. Clinical symptoms and signs are shown in **Table 2** [1–4].

○ (Muscle pain on mild exertion in the calf muscle, usually attributed to peripheral artery disease)

Diagnosis is based on the clinical picture, muscle biopsy, biochemical tests,

• Absence of increased venous lactate during forearm ischemic exercise test or cycle ergometry • Low or absent myophosphorylase activity on histochemical or biochemical examination of muscle

• Genetic testing (the muscle phosphorylase gene is located on chromosome 11q13, and several mutations

The absence of rising lactate is a diagnostic criterion in McAd. Usually this has been tested using the forearm ischemic exercise test [2–4]. Both Bollig [2] and Vissing and Haller [9] have suggested to use cycle ergometry testing instead of the forearm ischemic exercise test. The ischemic forearm exercise is more painful for the patients and might put them at risk for severe rhabdomyolysis and myoglobinuria. The cycle ergometry as diagnostic tool from sports medicine is useful in the diagnosis of McAd and may be used to assess the actual state of cardiopulmonary fitness and may help to give patients guidance for further training. **Figure 1** shows the results of cycle ergometry testing in a typical patient with McArdle disease [2].

**170**

**Table 3.**

• Clinical picture

biopsy

• Elevated creatine kinase (CK) levels in the blood

*Diagnosis of McArdle disease [2–4, 7, 9, 10].*

have been described—the most common mutation is called R50X)

At present there are no causal treatment options available. Some symptomatic treatment options may reduce symptoms or enhance the amount physical activity that can be tolerated. These treatment options include oral sucrose before exercise [11], a low dose of oral creatine [12], vitamin B6 [2, 10], and coenzyme Q10 [2, 10]. Our study about the use of clenbuterol over a 12-month period leads to a subjective improvement of exercise tolerance in three patients. Some relatives of the patients noted an improved exercise tolerance after clenbuterol intake over some weeks [2]. One patient from our study has used a low-dose clenbuterol (0.005–0.02 mg once daily) to enhance exercise tolerance for more than 10 years. This patient used clenbuterol for some months with regular breaks of weeks up to months between the therapy cycles. A systematic Cochrane review on pharmacological and nutritional treatment options has been published by Quinlivian et al. [12]. There do exist animal models for McArdle disease in sheep, cows, mice, and rats that may be used to test potential therapies in future studies [10]. Gene therapy of McArdle disease might be a future option, but its dangers outweigh the possible advantages at present [10].

#### **6. Health problems and possible risks associated with McArdle disease**

Patients with McArdle disease are at risk of developing myoglobinuria and even kidney failure due to rhabdomyolysis after exercise or anesthesia [2, 3, 12, 13]. Therefore, patients affected by McAd should learn how to accomplish daily activity with McAd and how to avoid major muscle damage and the risk for massive rhabdomyolysis and acute kidney failure.

Some cases with insulin resistance and a diabetes type II-like clinical picture in patients with McArdle have been described, but there is no known connection between type I diabetes and McArdle disease [10]. Increased glycogen storage in the muscle of McArdle patients has been suggested as a probable cause of insulin resistance in McArdle patients [10]. Overweight has been observed in many patients with McAd [14]. This might be a potential risk factor for developing type II diabetes as it is for other people without McArdle disease.

Another potential problem is the possible risk of malignant hyperthermia which is a complication during general anesthesia associated with different muscular diseases. Although no case of malignant hyperthermia during anesthesia has been described in McAd so far, it is a potential risk when patients with McAd have to undergo operations with the need for general anesthesia. Therefore, precautions have to be taken by the anesthesiologist, and local or regional anesthesia may be preferred whenever feasible [6, 13].

#### **7. Effects of physical activity and sports in patients with McArdle disease**

As described above patients with McAd might suffer from exercise intolerance and pain, fatigue, and cramps during exercise, typical clinical symptoms of McArdle disease. Up to 50% of the patients with McAd show myoglobinuria, and unfortunately acute renal failure has been described in 27% following rhabdomyolysis as a result of vigorous or strenuous exercise [3]. Cases with extreme rhabdomyolysis and myoglobinuria have, e.g., been reported after a swimming competition, an asthma attack, after carrying a TV, and after the diagnostic use of the ischemic work test using a tourniquet [15–19]. The variation of creatine kinase (CK) levels in the blood has been investigated in a male with McAd over a period of several months by the author [2]. **Figure 2** shows the results from this German doctor thesis from the year 2000. The results indicated that anaerobic exercise and physical activity demanding great strength or strenuous exercise lead to huge increases in creatine kinase activity, whereas aerobic exercise did not increase blood creatine kinase levels to a great extent. Aerobic exercise was shown to be associated with lower creatine kinase levels after physical activity in a number of instances during the study period [2, 20]. This finding was later proofed by other researchers [10]. The oxygen uptake and physical ability of patients affected by McAd is usually limited to about 50% of comparable healthy individuals [2].

#### **7.1 The second wind phenomenon**

The second wind phenomenon is defined as "a period of less painful and more effective exercise associated with a decrease in heart rate after the initial period of cramping and/or weakness." [21]. Many patients with McArdle disease do experience this phenomenon that was first described by Pearson et al. [22]. During exercise this phenomenon can lead to better endurance because patients are able to exercise for a longer period and experience physical activity as less painful in the long run.

#### **7.2 Aerobic exercise (endurance exercise)**

Aerobic exercise is endurance exercise where oxygen is needed in energy production. Aerobic energy production takes some minutes to start but can help to

**173**

**Figure 2.**

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy?*

supply energy for muscular activity over a longer period of time (several minutes up to several hours). Due to the lack of glucose that cannot be released from the glycogen deposits in the muscle, patients with McArdle disease rely on fatty acids, amino acids, and glucose from the liver as energy source during exercise [2, 10]. These mechanisms are based on aerobic metabolism. Patients with McAd can therefore tolerate longer periods of physical activity well if it is aerobic exercise of mild-to-moderate intensity. The work intensity that patients with McAd do tolerate

During the study period, different types of physical activity were recorded in a diary by the patient. Aerobic exercise as cycling and walking/hiking did not lead to

Different researchers have recommended aerobic training and aerobic conditioning in order to improve physical activity, oxygen uptake, cardiovascular fitness, and energy supply via the blood in McAd [2, 10, 23–26]. Especially walking and cycling with mild or moderate intensity can be recommended for all McAd

can show big variations between different patients.

CK elevation, whereas anaerobic exercise leads to CK elevation.

*Creatine kinase levels from a long-term follow-up over 5 months [modified from [2]].*

*DOI: http://dx.doi.org/10.5772/intechopen.89204*

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy? DOI: http://dx.doi.org/10.5772/intechopen.89204*

**Figure 2.** *Creatine kinase levels from a long-term follow-up over 5 months [modified from [2]].*

supply energy for muscular activity over a longer period of time (several minutes up to several hours). Due to the lack of glucose that cannot be released from the glycogen deposits in the muscle, patients with McArdle disease rely on fatty acids, amino acids, and glucose from the liver as energy source during exercise [2, 10]. These mechanisms are based on aerobic metabolism. Patients with McAd can therefore tolerate longer periods of physical activity well if it is aerobic exercise of mild-to-moderate intensity. The work intensity that patients with McAd do tolerate can show big variations between different patients.

During the study period, different types of physical activity were recorded in a diary by the patient. Aerobic exercise as cycling and walking/hiking did not lead to CK elevation, whereas anaerobic exercise leads to CK elevation.

Different researchers have recommended aerobic training and aerobic conditioning in order to improve physical activity, oxygen uptake, cardiovascular fitness, and energy supply via the blood in McAd [2, 10, 23–26]. Especially walking and cycling with mild or moderate intensity can be recommended for all McAd

*Cellular Metabolism and Related Disorders*

myolysis and acute kidney failure.

preferred whenever feasible [6, 13].

**with McArdle disease**

as it is for other people without McArdle disease.

**7. Effects of physical activity and sports in patients** 

limited to about 50% of comparable healthy individuals [2].

**7.1 The second wind phenomenon**

**7.2 Aerobic exercise (endurance exercise)**

with McAd and how to avoid major muscle damage and the risk for massive rhabdo-

Some cases with insulin resistance and a diabetes type II-like clinical picture in patients with McArdle have been described, but there is no known connection between type I diabetes and McArdle disease [10]. Increased glycogen storage in the muscle of McArdle patients has been suggested as a probable cause of insulin resistance in McArdle patients [10]. Overweight has been observed in many patients with McAd [14]. This might be a potential risk factor for developing type II diabetes

Another potential problem is the possible risk of malignant hyperthermia which

is a complication during general anesthesia associated with different muscular diseases. Although no case of malignant hyperthermia during anesthesia has been described in McAd so far, it is a potential risk when patients with McAd have to undergo operations with the need for general anesthesia. Therefore, precautions have to be taken by the anesthesiologist, and local or regional anesthesia may be

As described above patients with McAd might suffer from exercise intolerance and pain, fatigue, and cramps during exercise, typical clinical symptoms of McArdle disease. Up to 50% of the patients with McAd show myoglobinuria, and unfortunately acute renal failure has been described in 27% following rhabdomyolysis as a result of vigorous or strenuous exercise [3]. Cases with extreme rhabdomyolysis and myoglobinuria have, e.g., been reported after a swimming competition, an asthma attack, after carrying a TV, and after the diagnostic use of the ischemic work test using a tourniquet [15–19]. The variation of creatine kinase (CK) levels in the blood has been investigated in a male with McAd over a period of several months by the author [2]. **Figure 2** shows the results from this German doctor thesis from the year 2000. The results indicated that anaerobic exercise and physical activity demanding great strength or strenuous exercise lead to huge increases in creatine kinase activity, whereas aerobic exercise did not increase blood creatine kinase levels to a great extent. Aerobic exercise was shown to be associated with lower creatine kinase levels after physical activity in a number of instances during the study period [2, 20]. This finding was later proofed by other researchers [10]. The oxygen uptake and physical ability of patients affected by McAd is usually

The second wind phenomenon is defined as "a period of less painful and more effective exercise associated with a decrease in heart rate after the initial period of cramping and/or weakness." [21]. Many patients with McArdle disease do experience this phenomenon that was first described by Pearson et al. [22]. During exercise this phenomenon can lead to better endurance because patients are able to exercise for a longer period and experience physical activity as less painful in the long run.

Aerobic exercise is endurance exercise where oxygen is needed in energy production. Aerobic energy production takes some minutes to start but can help to

**172**

patients to improve their physical capacity [2, 10, 25–27]. Aerobic metabolism usually starts after 7–10 min of exercising. Therefore, patients with McAd should warm up with low intensity and may increase the intensity of physical work after 7–10 min. Some of the patients experience the above described second wind phenomenon.

#### **7.3 Anaerobic exercise**

During anaerobic exercise (within the first seconds and minutes or using great strength), energy is supplied by anaerobic mechanisms as anaerobic glycogenolysis without oxygen. Short periods of activity with high intensity such as running, walking upstairs, and carrying or lifting heavy weights require anaerobic metabolism. Due to the deficiency of the myophosphorylase enzyme in the muscle of McAd patients, this is hampered. Anaerobic physical activity can thus lead to muscular damage in patients with McAd and should be avoided as far as possible by patients with McAd [2, 10, 25]. Nevertheless supervised resistance training has been shown to improve muscle strength in patients with McAd [28]. Pietrusz et al. state that strength training for McArdle patients is safe when it is tailored to the patient as "short bursts of resistance activity lasting no longer than 10 seconds preceded and followed by 30 seconds to 3 minutes rest." In a case report of two McAd patients, an improvement of both muscular strength and quality of life was observed after a period with resistance training [29].

#### **8. Discussion and conclusions**

Sport is the most important therapeutical option for patients with McArdle disease. Aerobic conditioning can be recommended to all McAd patients, but anaerobic exercise may lead to muscular damage. It has been shown by different researchers that regular physical activity may lead to improved exercise capacity [2, 10, 23–26]. As we have learned from practical experience and the scientific literature, extensive physical and strenuous exercise may lead to muscle damage, myoglobinuria, and even acute kidney failure [15–19]. Nevertheless Santalla et al. and Pietrusz et al. have shown that resistance training under expert supervision is feasible and improves muscle strength in McArdle patients. But it is important that this type of training is performed under supervision in order to avoid muscle damage [28, 29]. On the other hand, a case study with a long-term follow-up of one patient with McAd has shown that mostly aerobic activity did not lead to an increase in the creatine kinase level. Instead, moderate cycling or hiking led to a decrease in the creatine kinase [2]. In the same patient, anaerobic exercise lead to increased CK levels suggesting muscle damage after carrying heavy weights [2]. In order to avoid muscle damage by vigorous exercise or in a risky way, all patients with McAd should receive sport medical advice on an individualized training plan that meets their individual training needs. In order to enhance patient compliance, common aims and routines for physical activity and sports should be established.

In conclusion, regular activity and sport are paramount for patients with McArdle disease. Patients benefit from regular physical activity. Sport should be based on aerobic conditioning such as walking and cycling, whereas anaerobic exercise of high intensity over short periods should be avoided in general. Physical activity must be individualized to the patients' capacity and needs. Some case

**175**

activity.

**Table 4.**

is needed.

medicine.

[2, 10, 20–30].

**Conflict of interest**

The author declares no conflict of interest.

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy?*

reports suggest that even resistance training might be feasible, effective, and safe for patients with McAd. Obviously there is individual variation of the intensity that is appropriate for different patients. Therefore, a cooperation with a doctor experienced on sports medicine, trainer, and physiotherapist can help to establish an individualized training plan in order to maintain and possibly to improve physical capacity without increasing the danger for undesirable effects of too much physical

• Aerobic conditioning (walking or cycling) is the preferable training method for patients with McAd. • Keep on doing physical activity on a regular basis three to five times a week using aerobic exercise, such

• Regular training of mild-to-moderate intensity will improve physical capacity and may postpone weak-

• Resistance training should only be used under competent supervision of physicians and/or physiothera-

pists with experience in treating McArdle patients in order to avoid muscle damage.

Probably a self-monitoring of the CK blood level (like measuring blood-glucose in diabetes patients) could help to guide training and individual response to exercise in the future. More research on specially designed training programs for McAd

The following general recommendations shown in **Table 4** are based on personal experience of the author and the current state of the scientific literature

As shown above, sport has therapeutic potential for people with McArdle disease. Sport is used with reason and is therefore not a danger but a powerful

*DOI: http://dx.doi.org/10.5772/intechopen.89204*

ness and muscle wasting in elderly patients.

as walking or cycling for about 30–40 min on each occasion.

• Preexercise nutrition may enhance physical performance.

*Recommendations for physical activity for patients with McArdle disease.*

• Do not be afraid of physical activity. • Individualize your personal training goals. • Compete with yourself and not with others.


#### **Table 4.**

*Cellular Metabolism and Related Disorders*

phenomenon.

**7.3 Anaerobic exercise**

tance training [29].

**8. Discussion and conclusions**

patients to improve their physical capacity [2, 10, 25–27]. Aerobic metabolism usually starts after 7–10 min of exercising. Therefore, patients with McAd should warm up with low intensity and may increase the intensity of physical work after 7–10 min. Some of the patients experience the above described second wind

During anaerobic exercise (within the first seconds and minutes or using great strength), energy is supplied by anaerobic mechanisms as anaerobic glycogenolysis without oxygen. Short periods of activity with high intensity such as running, walking upstairs, and carrying or lifting heavy weights require anaerobic metabolism. Due to the deficiency of the myophosphorylase enzyme in the muscle of McAd patients, this is hampered. Anaerobic physical activity can thus lead to muscular damage in patients with McAd and should be avoided as far as possible by patients with McAd [2, 10, 25]. Nevertheless supervised resistance training has been shown to improve muscle strength in patients with McAd [28]. Pietrusz et al. state that strength training for McArdle patients is safe when it is tailored to the patient as "short bursts of resistance activity lasting no longer than 10 seconds preceded and followed by 30 seconds to 3 minutes rest." In a case report of two McAd patients, an improvement of both muscular strength and quality of life was observed after a period with resis-

Sport is the most important therapeutical option for patients with McArdle disease. Aerobic conditioning can be recommended to all McAd patients, but anaerobic exercise may lead to muscular damage. It has been shown by different researchers that regular physical activity may lead to improved exercise capacity [2, 10, 23–26]. As we have learned from practical experience and the scientific literature, extensive physical and strenuous exercise may lead to muscle damage, myoglobinuria, and even acute kidney failure [15–19]. Nevertheless Santalla et al. and Pietrusz et al. have shown that resistance training under expert supervision is feasible and improves muscle strength in McArdle patients. But it is important that this type of training is performed under supervision in order to avoid muscle damage [28, 29]. On the other hand, a case study with a long-term follow-up of one patient with McAd has shown that mostly aerobic activity did not lead to an increase in the creatine kinase level. Instead, moderate cycling or hiking led to a decrease in the creatine kinase [2]. In the same patient, anaerobic exercise lead to increased CK levels suggesting muscle damage after carrying heavy weights [2]. In order to avoid muscle damage by vigorous exercise or in a risky way, all patients with McAd should receive sport medical advice on an individualized training plan that meets their individual training needs. In order to enhance patient compliance, common aims and routines for physical activity and sports should be

In conclusion, regular activity and sport are paramount for patients with McArdle disease. Patients benefit from regular physical activity. Sport should be based on aerobic conditioning such as walking and cycling, whereas anaerobic exercise of high intensity over short periods should be avoided in general. Physical activity must be individualized to the patients' capacity and needs. Some case

**174**

established.

*Recommendations for physical activity for patients with McArdle disease.*

reports suggest that even resistance training might be feasible, effective, and safe for patients with McAd. Obviously there is individual variation of the intensity that is appropriate for different patients. Therefore, a cooperation with a doctor experienced on sports medicine, trainer, and physiotherapist can help to establish an individualized training plan in order to maintain and possibly to improve physical capacity without increasing the danger for undesirable effects of too much physical activity.

Probably a self-monitoring of the CK blood level (like measuring blood-glucose in diabetes patients) could help to guide training and individual response to exercise in the future. More research on specially designed training programs for McAd is needed.

The following general recommendations shown in **Table 4** are based on personal experience of the author and the current state of the scientific literature [2, 10, 20–30].

As shown above, sport has therapeutic potential for people with McArdle disease. Sport is used with reason and is therefore not a danger but a powerful medicine.

#### **Conflict of interest**

The author declares no conflict of interest.

*Cellular Metabolism and Related Disorders*

#### **Author details**

Georg Bollig1,2

1 Palliative Care Team, Medical Department Sønderborg/Tønder, South Jutland Hospital, Sønderborg, Denmark

2 Medical Research Unit, Institute of Regional Health Research, University of Southern Denmark, Odense, Denmark

\*Address all correspondence to: georg.bollig@rsyd.dk

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**177**

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy?*

[11] Vissing J, Haller RG. The effect of oral sucrose on exercise tolerance in patients with McArdle's disease. The New England Journal of Medicine.

2003;**349**:2503-2509

[12] Quinlivan R, Beynon RJ, Quinlivan R, et al. Pharmacological and nutritional treatment for McArdle's disease (glycogen storage disease type V). Cochrane Database of Systematic

Reviews. 2004;**3**:CD003458

disease and anaesthesia. Case

[13] Bollig G, Mohr S, Ræder J. McArdle's

reports, review of potential problems and association with malignant hyperthermia. Acta Anaesthesiologica Scandinavica. 2005;**49**:1077-1083

[14] Quinlivian R, Buckley J, James M, Twist A, Ball S, Duno M, et al. McArdle disease: A clinical review. Journal of Neurology, Neurosurgery, and Psychiatry. 2010;**81**(11):1182-1188

[15] Stamos GE, Crouch TT, Wood WG, et al. Acute renal failure in McArdle's disease. Southern Medical Journal.

[17] Tsushima K, Koyama S, Ueno M, et al. Rhabdomyolysis triggered by an asthmatic attack in a patient with McArdle disease. Internal Medicine. 2001;**40**:131-134

[16] McMillan MA, Hallworth MJ, Doyle D, et al. Acute renal failure due to McArdle's disease. Renal Failure.

[18] Bundschuh HD, Pfeiffer J,

Medizin. 1977;**83**:1280-1293

[19] Meinck HM, Goebel HH, Rumpf KW, et al. The forearm ischaemic work test-hazardous to McArdle patients? Journal of Neurology,

Schlote W. Akutes Nierenversagen bei McArdle-Syndrom. Verhandlungen der Deutschen Gesellschaft für Innere

1979;**72**:77-79

1989;**11**:23-25

*DOI: http://dx.doi.org/10.5772/intechopen.89204*

[1] McArdle B. Myopathy due to a defect in muscle glycogen breakdown. Clinical

[2] Bollig G. Das McArdle-Syndrom

sportmedizinischen Gesichtspunkten. Köln: Inaugural-Dissertation Universität

[4] Bartram C, Edwards RHT, Beynon RJ. McArdle's disease-muscle glycogen phosphorylase deficiency. Biochimica et Biophysica Acta. 1995;**1272**:1-13

[5] Di Mauro S. Muscle glycogenoses: An overview. Acta Myologica.

[6] Bollig G. McArdle's disease (glycogen storage disease type V) and anesthesia—A case report and review of the literature. Pediatric Anesthesia. 2013;**23**(9):817-823

[7] Kubisch C, Wicklein EM, Jentsch TJ. Molecular diagnosis of McArdle disease:

[8] Haller RG. Treatment of McArdle disease. Archives of Neurology.

[9] Vissing J, Haller RG. A diagnostic cycle test for McArdle's disease. Annals

[10] Birch KE. Das McArdle-Handbuch.

of Neurology. 2003;**54**:539-542

Deutschland: Selbsthilfegruppe Glykogenose; 2011. Available from: https://www.glykogenose.de/ download/McArdle\_Handbuch\_DEU\_

Revised genomic structure of the myophosphorylase gene and identification of a novel mutation. Human Mutation. 1998;**12**:27-32

**References**

zu Köln; 2000

Science. 1951;**24**:13-35

(Glykogenose Typ 5) unter

[3] DiMauro S, Tsujino S. Nonlysosomal glycogenoses. In: Engel AG, Franzini-Armstrong C, editors. Myology. New York: McGraw-

Hill; 1994. pp. 1554-1576

2007;**XXVI**:35-41

2000;**57**:923-924

Final\_20\_04\_18.pdf

*Sports and McArdle Disease (Glycogen Storage Disease Type V): Danger or Therapy? DOI: http://dx.doi.org/10.5772/intechopen.89204*

#### **References**

*Cellular Metabolism and Related Disorders*

**176**

**Author details**

Hospital, Sønderborg, Denmark

Southern Denmark, Odense, Denmark

provided the original work is properly cited.

\*Address all correspondence to: georg.bollig@rsyd.dk

1 Palliative Care Team, Medical Department Sønderborg/Tønder, South Jutland

2 Medical Research Unit, Institute of Regional Health Research, University of

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Georg Bollig1,2

[1] McArdle B. Myopathy due to a defect in muscle glycogen breakdown. Clinical Science. 1951;**24**:13-35

[2] Bollig G. Das McArdle-Syndrom (Glykogenose Typ 5) unter sportmedizinischen Gesichtspunkten. Köln: Inaugural-Dissertation Universität zu Köln; 2000

[3] DiMauro S, Tsujino S. Nonlysosomal glycogenoses. In: Engel AG, Franzini-Armstrong C, editors. Myology. New York: McGraw-Hill; 1994. pp. 1554-1576

[4] Bartram C, Edwards RHT, Beynon RJ. McArdle's disease-muscle glycogen phosphorylase deficiency. Biochimica et Biophysica Acta. 1995;**1272**:1-13

[5] Di Mauro S. Muscle glycogenoses: An overview. Acta Myologica. 2007;**XXVI**:35-41

[6] Bollig G. McArdle's disease (glycogen storage disease type V) and anesthesia—A case report and review of the literature. Pediatric Anesthesia. 2013;**23**(9):817-823

[7] Kubisch C, Wicklein EM, Jentsch TJ. Molecular diagnosis of McArdle disease: Revised genomic structure of the myophosphorylase gene and identification of a novel mutation. Human Mutation. 1998;**12**:27-32

[8] Haller RG. Treatment of McArdle disease. Archives of Neurology. 2000;**57**:923-924

[9] Vissing J, Haller RG. A diagnostic cycle test for McArdle's disease. Annals of Neurology. 2003;**54**:539-542

[10] Birch KE. Das McArdle-Handbuch. Deutschland: Selbsthilfegruppe Glykogenose; 2011. Available from: https://www.glykogenose.de/ download/McArdle\_Handbuch\_DEU\_ Final\_20\_04\_18.pdf

[11] Vissing J, Haller RG. The effect of oral sucrose on exercise tolerance in patients with McArdle's disease. The New England Journal of Medicine. 2003;**349**:2503-2509

[12] Quinlivan R, Beynon RJ, Quinlivan R, et al. Pharmacological and nutritional treatment for McArdle's disease (glycogen storage disease type V). Cochrane Database of Systematic Reviews. 2004;**3**:CD003458

[13] Bollig G, Mohr S, Ræder J. McArdle's disease and anaesthesia. Case reports, review of potential problems and association with malignant hyperthermia. Acta Anaesthesiologica Scandinavica. 2005;**49**:1077-1083

[14] Quinlivian R, Buckley J, James M, Twist A, Ball S, Duno M, et al. McArdle disease: A clinical review. Journal of Neurology, Neurosurgery, and Psychiatry. 2010;**81**(11):1182-1188

[15] Stamos GE, Crouch TT, Wood WG, et al. Acute renal failure in McArdle's disease. Southern Medical Journal. 1979;**72**:77-79

[16] McMillan MA, Hallworth MJ, Doyle D, et al. Acute renal failure due to McArdle's disease. Renal Failure. 1989;**11**:23-25

[17] Tsushima K, Koyama S, Ueno M, et al. Rhabdomyolysis triggered by an asthmatic attack in a patient with McArdle disease. Internal Medicine. 2001;**40**:131-134

[18] Bundschuh HD, Pfeiffer J, Schlote W. Akutes Nierenversagen bei McArdle-Syndrom. Verhandlungen der Deutschen Gesellschaft für Innere Medizin. 1977;**83**:1280-1293

[19] Meinck HM, Goebel HH, Rumpf KW, et al. The forearm ischaemic work test-hazardous to McArdle patients? Journal of Neurology, Neurosurgery, and Psychiatry. 1982;**45**:1144-1146

[20] Bollig G. Improvement of exercise tolerance in McArdles disease—Lessons learned from sports medicine. In: Poster Presentation International GSD Conference 2013 (IGSD13). Germany: Heidelberg; 2013

[21] Scalco RS, Chatfield S, Godfrey R, Pattni J, Ellerton C, Beggs A, et al. From exercise intolerance to functional improvement: The second wind phenomenon in the identification of McArdle disease. Arquivos de Neuro-Psiquiatria. 2014;**72**(7):538-541

[22] Pearson CM, Rimer DG, Mommaerts WF. A metabolic myopathy due to absence of muscle phosphorylase. The American Journal of Medicine. 1961;**30**:502-517

[23] Perez M, Moran M, Cardona C, et al. Can patients with McArdle's disease run? British Journal of Sports Medicine. 2007;**41**:53-54

[24] Haller RG, Wyrick P, Taivassolo T, et al. Aerobic conditioning: An effective therapy in McArdle's disease. Annals of Neurology. 2006;**59**:922-928

[25] National Commissioning Group. McArdle Disease Service. Exercise and McArdle Disease. London: University College London Hospitals; 2016. Available from: https://www. uclh.nhs.uk/PandV/PIL/Patient%20 information%20leaflets/Exercise%20 and%20McArdle%20Disease.pdf

[26] Quinlivan R, Vissing J, Hilton-Jones D, Buckley J. Physical training for McArdle disease. Cochrane Database of Systematic Reviews. 2011;**12**:CD007931

[27] Reason SL. One Step at a Time— Walking with McArdle Disease. Droxford: Association for Glycogen Storage Disease; 2013

[28] Santalla A, Munguía-Izquierdo D, Brea-Alejo L, Pagola-Aldazábal I, Díez-Bermejo J, Fleck SJ, et al. Feasibility of resistance training in adult McArdle patients: Clinical outcomes and muscle strength and mass benefits. Frontiers in Aging Neuroscience. 2014;**6**:334

[29] Pietrusz A, Scalco RS, Quinlivan R. Case report resistance exercise training in McArdle disease: Myth or reality? Case Reports in Neurological Medicine. 2018;**2018**:9658251

[30] Nogales-Gadea G, Santalla A, Ballester-Lopez A, Arenas J, Martín MA, Godfrey R, et al. Exercise and preexercise nutrition as treatment for McArdle disease. Medicine and Science in Sports and Exercise. 2016;**48**(4):673-679

**179**

Section 8

Imaging Studies

Section 8 Imaging Studies

*Cellular Metabolism and Related Disorders*

[20] Bollig G. Improvement of exercise tolerance in McArdles disease—Lessons learned from sports medicine. In: Poster Presentation International GSD Conference 2013 (IGSD13). Germany:

[28] Santalla A, Munguía-Izquierdo D, Brea-Alejo L, Pagola-Aldazábal I, Díez-Bermejo J, Fleck SJ, et al.

Feasibility of resistance training in adult McArdle patients: Clinical outcomes and muscle strength and mass benefits. Frontiers in Aging Neuroscience.

2014;**6**:334

[29] Pietrusz A, Scalco RS,

2018;**2018**:9658251

2016;**48**(4):673-679

Quinlivan R. Case report resistance exercise training in McArdle disease: Myth or reality? Case Reports in Neurological Medicine.

[30] Nogales-Gadea G, Santalla A, Ballester-Lopez A, Arenas J,

Martín MA, Godfrey R, et al. Exercise and preexercise nutrition as treatment for McArdle disease. Medicine and Science in Sports and Exercise.

[21] Scalco RS, Chatfield S, Godfrey R, Pattni J, Ellerton C, Beggs A, et al. From exercise intolerance to functional

Mommaerts WF. A metabolic myopathy due to absence of muscle phosphorylase. The American Journal of Medicine.

[23] Perez M, Moran M, Cardona C, et al. Can patients with McArdle's disease run? British Journal of Sports Medicine.

[24] Haller RG, Wyrick P, Taivassolo T, et al. Aerobic conditioning: An effective therapy in McArdle's disease. Annals of

[25] National Commissioning Group. McArdle Disease Service. Exercise and McArdle Disease. London: University College London Hospitals; 2016. Available from: https://www. uclh.nhs.uk/PandV/PIL/Patient%20 information%20leaflets/Exercise%20 and%20McArdle%20Disease.pdf

[26] Quinlivan R, Vissing J, Hilton-Jones D, Buckley J. Physical training for McArdle

Systematic Reviews. 2011;**12**:CD007931

[27] Reason SL. One Step at a Time— Walking with McArdle Disease. Droxford: Association for Glycogen

disease. Cochrane Database of

Storage Disease; 2013

Neurology. 2006;**59**:922-928

improvement: The second wind phenomenon in the identification of McArdle disease. Arquivos de Neuro-Psiquiatria. 2014;**72**(7):538-541

[22] Pearson CM, Rimer DG,

Neurosurgery, and Psychiatry.

1982;**45**:1144-1146

Heidelberg; 2013

1961;**30**:502-517

2007;**41**:53-54

**178**

**181**

**Chapter 11**

**Abstract**

*Andrea L. Gropman*

on development of working memory.

**1. Introduction**

Emerging Knowledge From

Ammonia Control Enough?

Noninvasive Imaging Studies: Is

Multiple lines of research suggest that ammonia is harmful to the brain if the levels remain elevated for extended periods of time. Several decades ago, there was no testing or standard of care to monitor the effect of hyperammonemia (HA) on neurological function in urea cycle disorders (UCD), and the timing of HA encephalopathy is still not clear. Magnetic resonance imaging (MRI) was not done routinely, if at all, so it was not known what changes were occurring in the brain, during and after recovery from HA. Decades ago, a diagnosis of a UCD meant severe disability and early death. Earlier diagnosis, improved management, and nitrogen scavenger therapy have improved the lives and life span of patients with UCD. However, many patients suffer from learning difficulties under the umbrella "executive function" which comprises neurologically based skills involving mental control and self-regulation. The general agreement of the core elements of executive functions includes inhibition, working memory, and cognitive flexibility and is necessary in development of skills in reasoning, fluid intelligence, problem-solving,

and planning. Our research focuses on the use of noninvasive neuroimaging coupled with neuropsychological testing to understand the complex relationship between ammonia, glutamine, cognitive function, seizures, and specifically impact

**Keywords:** ammonia, EEG, glutamine, MRI, neuroimaging, urea cycle disorder

associated with less severe phenotypes and later onset presentation [10].

The urea cycle disorders (UCD) represent one of the most common groups of inborn errors of metabolism, with an overall incidence of 1 in 30,000 [1, 2], and involve deficiency of one of six urea cycle enzymes or of a related cofactor or transporter [3, 4]. The most common of these, ornithine transcarbamylase deficiency (OTCD), is the only disorder of ureagenesis inherited in an X-linked manner, with an estimated incidence of 1 in 70,000 [5]. Over 240 missense mutations have been identified in the OTCD gene but overall 400 including nonsense, frameshift, in-frame indels, splice site errors, and one in a regulatory domain [6, 7]. About 60% of hemizygous males harbor a mutation around the enzyme active site and present with hyperammonemic (HA) coma in the newborn period [8, 9]. The remaining 40% of patients demonstrate more peripheral mutations in other parts of the gene,

#### **Chapter 11**

## Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?

*Andrea L. Gropman*

#### **Abstract**

Multiple lines of research suggest that ammonia is harmful to the brain if the levels remain elevated for extended periods of time. Several decades ago, there was no testing or standard of care to monitor the effect of hyperammonemia (HA) on neurological function in urea cycle disorders (UCD), and the timing of HA encephalopathy is still not clear. Magnetic resonance imaging (MRI) was not done routinely, if at all, so it was not known what changes were occurring in the brain, during and after recovery from HA. Decades ago, a diagnosis of a UCD meant severe disability and early death. Earlier diagnosis, improved management, and nitrogen scavenger therapy have improved the lives and life span of patients with UCD. However, many patients suffer from learning difficulties under the umbrella "executive function" which comprises neurologically based skills involving mental control and self-regulation. The general agreement of the core elements of executive functions includes inhibition, working memory, and cognitive flexibility and is necessary in development of skills in reasoning, fluid intelligence, problem-solving, and planning. Our research focuses on the use of noninvasive neuroimaging coupled with neuropsychological testing to understand the complex relationship between ammonia, glutamine, cognitive function, seizures, and specifically impact on development of working memory.

**Keywords:** ammonia, EEG, glutamine, MRI, neuroimaging, urea cycle disorder

#### **1. Introduction**

The urea cycle disorders (UCD) represent one of the most common groups of inborn errors of metabolism, with an overall incidence of 1 in 30,000 [1, 2], and involve deficiency of one of six urea cycle enzymes or of a related cofactor or transporter [3, 4]. The most common of these, ornithine transcarbamylase deficiency (OTCD), is the only disorder of ureagenesis inherited in an X-linked manner, with an estimated incidence of 1 in 70,000 [5]. Over 240 missense mutations have been identified in the OTCD gene but overall 400 including nonsense, frameshift, in-frame indels, splice site errors, and one in a regulatory domain [6, 7]. About 60% of hemizygous males harbor a mutation around the enzyme active site and present with hyperammonemic (HA) coma in the newborn period [8, 9]. The remaining 40% of patients demonstrate more peripheral mutations in other parts of the gene, associated with less severe phenotypes and later onset presentation [10].

A majority of children with OTCD have cognitive and motor deficits due to hyperammonemic episodes [8, 11–13]. Neonatal onset disease mortality rate is high. Prior to advances in recognition and treatment, it was not uncommon for survivors of neonatal onset disease to have intellectual disability, cerebral palsy, and seizures [14]. Neonatal survivors have a decreased IQ which may be as low as 43. In males with partial deficiencies, disease onset is later, and outcome is better, although still associated with high mortality and morbidity with many individuals manifesting cognitive, motor, and psychiatric sequelae [15–17], in particular impaired working memory and other measures of executive function which are essential for performing well in school, vocations, and relationships. Treatment of OTCD involves a combination of protein restriction (which is also a restriction in nitrogen, leading to ammonia accumulation) and medications that invoke an alternative pathway of waste nitrogen excretion [18, 19]. Females heterozygous for OTCD have a variable phenotype and display a broad range of symptoms from apparently asymptomatic to fully affected, owing to both allelic heterogeneity and differential X-inactivation patterns.

A common presumption for years has been that approximately 85% of heterozygous females are asymptomatic based on history, whereas the remainder show symptoms ranging from behavioral and learning disabilities and protein intolerance to cyclical vomiting, stroke-like episodes, and hyperammonemic coma [20–23]. Symptomatic women who harbor mutations seen in the neonatal onset disorder in hemizygous males [10] may develop HA due to skewed X-inactivation. There is therefore a range of residual enzyme capacities and urea synthetic capacities that result in this variation [24]. However, advances in neuroimaging and the work of the Urea Cycle Disorders Consortium (UCDC) have demonstrated that many of these previously presumed asymptomatic females have similar brain structural, biochemical, and cognitive biomarkers seen in those who are clinically impacted, yet they may be mild under conditions of low demand. More obvious symptoms were uncovered when cognitive demand increases or there is superimposed illness or stressor [25].

#### **2. Pathophysiology of the UCDs**

Ammonia is a product of the metabolism of proteins and other compounds, and it is required for the synthesis of essential cellular compounds. However, a five- to tenfold increase in ammonia in the blood induces toxic effects in most animal species, with alterations in the function of the central nervous system. Ammonia is a normal constituent of all body fluids. At physiologic pH, it exists mainly as ammonium ion. Reference serum levels are less than 35 mmol/L (outside the newborn period, where higher levels are seen). Excess ammonia is excreted as urea, which is synthesized in the liver through the urea cycle. Sources of ammonia include bacterial hydrolysis of urea and other nitrogenous compounds in the intestine, the purine-nucleotide cycle and amino acid transamination in skeletal muscle, and other metabolic processes in the kidneys and liver. Increased entry of ammonia to the brain is a primary cause of neurological disorders associated with HA, such as congenital deficiencies of urea cycle enzymes, hepatic encephalopathies, Reye syndrome, several other metabolic disorders, and some toxic encephalopathies [26–28].

On the basis of studies in animal models and other preclinical model systems, several mechanisms of ammonia neurotoxicity at the molecular level have been proposed.

**183**

**Figure 1.**

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

tion of HA coma and the interval between coma and death [28].

decreases in brain glycogen, ketone bodies, and glutamate [30].

While the exact pathophysiology remains unclear, current theories include (1) glutamine accumulation, with associated impaired cerebral osmoregulation, and (2) glutamate/*N*-methyl D-aspartate (NMDA) receptor activation, with resultant excitotoxic injury and energy deficit [26–30]. The WM is preferentially affected in proximal UCD, and the extent of injury has been shown to depend upon the dura-

Acute ammonia intoxication in an animal model leads to increased extracellular

quence of decreased phosphorylation by protein kinase C. Activation of the NMDA receptor may account for seizures seen in some patients during acute HA [29].

Chronic HA is associated with an increase in inhibitory neurotransmission as a consequence of two factors. The first involves the downregulation of glutamate receptors secondary to excessive extrasynaptic accumulation of glutamate. The second mechanism implies increased GABAergic tone resulting from benzodiazepine receptor overstimulation by endogenous benzodiazepines and neurosteroids. These changes likely play a role in central nervous system features of intellectual function,

In the brain, glutamine represents a storage depot for nitrogen, binding excess ammonia and offering a short-term buffering of excess ammonia in patients with HA, likely as a protective mechanism. It is these high levels of glutamine in the brain that are also hypothesized to be neurotoxic and one of the factors leading to injury (UCDC unpublished). Brain astrocytes are key players in the interactions of

*The glutamine-glutamate cycle. Reprinted with permission from Pediatric Health, 2008, 2(6):701–713.*

High levels of ammonia in the brain also induce other metabolic changes that are not mediated by activation of the NMDA receptor and thus are not involved directly in ammonia-induced ATP depletion or neurotoxicity. These include increases in brain levels of lactate, pyruvate, glutamine, and glucose, with concomitant

/K+


concentration of glutamate in the brain and results in activation of the NMDA receptor. Activation of this receptor mediates ATP depletion and ammonia toxicity; blocking the NMDA receptor with dizocilpine (MK-801) prevents both phenomena.

*DOI: http://dx.doi.org/10.5772/intechopen.90025*

The ATP depletion is due to activation of Na+

decreased consciousness, and coma [26, 30].

glutamine and ammonia via the Gln/Glu cycle (**Figure 1**).

#### *Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough? DOI: http://dx.doi.org/10.5772/intechopen.90025*

While the exact pathophysiology remains unclear, current theories include (1) glutamine accumulation, with associated impaired cerebral osmoregulation, and (2) glutamate/*N*-methyl D-aspartate (NMDA) receptor activation, with resultant excitotoxic injury and energy deficit [26–30]. The WM is preferentially affected in proximal UCD, and the extent of injury has been shown to depend upon the duration of HA coma and the interval between coma and death [28].

Acute ammonia intoxication in an animal model leads to increased extracellular concentration of glutamate in the brain and results in activation of the NMDA receptor. Activation of this receptor mediates ATP depletion and ammonia toxicity; blocking the NMDA receptor with dizocilpine (MK-801) prevents both phenomena. The ATP depletion is due to activation of Na+ /K+ -ATPase, which, in turn, is a consequence of decreased phosphorylation by protein kinase C. Activation of the NMDA receptor may account for seizures seen in some patients during acute HA [29].

High levels of ammonia in the brain also induce other metabolic changes that are not mediated by activation of the NMDA receptor and thus are not involved directly in ammonia-induced ATP depletion or neurotoxicity. These include increases in brain levels of lactate, pyruvate, glutamine, and glucose, with concomitant decreases in brain glycogen, ketone bodies, and glutamate [30].

Chronic HA is associated with an increase in inhibitory neurotransmission as a consequence of two factors. The first involves the downregulation of glutamate receptors secondary to excessive extrasynaptic accumulation of glutamate. The second mechanism implies increased GABAergic tone resulting from benzodiazepine receptor overstimulation by endogenous benzodiazepines and neurosteroids. These changes likely play a role in central nervous system features of intellectual function, decreased consciousness, and coma [26, 30].

In the brain, glutamine represents a storage depot for nitrogen, binding excess ammonia and offering a short-term buffering of excess ammonia in patients with HA, likely as a protective mechanism. It is these high levels of glutamine in the brain that are also hypothesized to be neurotoxic and one of the factors leading to injury (UCDC unpublished). Brain astrocytes are key players in the interactions of glutamine and ammonia via the Gln/Glu cycle (**Figure 1**).

*Cellular Metabolism and Related Disorders*

differential X-inactivation patterns.

**2. Pathophysiology of the UCDs**

or stressor [25].

A majority of children with OTCD have cognitive and motor deficits due to hyperammonemic episodes [8, 11–13]. Neonatal onset disease mortality rate is high. Prior to advances in recognition and treatment, it was not uncommon for survivors of neonatal onset disease to have intellectual disability, cerebral palsy, and seizures [14]. Neonatal survivors have a decreased IQ which may be as low as 43. In males with partial deficiencies, disease onset is later, and outcome is better, although still associated with high mortality and morbidity with many individuals manifesting cognitive, motor, and psychiatric sequelae [15–17], in particular impaired working memory and other measures of executive function which are essential for performing well in school, vocations, and relationships. Treatment of OTCD involves a combination of protein restriction (which is also a restriction in nitrogen, leading to ammonia accumulation) and medications that invoke an alternative pathway of waste nitrogen excretion [18, 19]. Females heterozygous for OTCD have a variable phenotype and display a broad range of symptoms from apparently asymptomatic to fully affected, owing to both allelic heterogeneity and

A common presumption for years has been that approximately 85% of heterozygous females are asymptomatic based on history, whereas the remainder show symptoms ranging from behavioral and learning disabilities and protein intolerance to cyclical vomiting, stroke-like episodes, and hyperammonemic coma [20–23]. Symptomatic women who harbor mutations seen in the neonatal onset disorder in hemizygous males [10] may develop HA due to skewed X-inactivation. There is therefore a range of residual enzyme capacities and urea synthetic capacities that result in this variation [24]. However, advances in neuroimaging and the work of the Urea Cycle Disorders Consortium (UCDC) have demonstrated that many of these previously presumed asymptomatic females have similar brain structural, biochemical, and cognitive biomarkers seen in those who are clinically impacted, yet they may be mild under conditions of low demand. More obvious symptoms were uncovered when cognitive demand increases or there is superimposed illness

Ammonia is a product of the metabolism of proteins and other compounds, and it is required for the synthesis of essential cellular compounds. However, a five- to tenfold increase in ammonia in the blood induces toxic effects in most animal species, with alterations in the function of the central nervous system. Ammonia is a normal constituent of all body fluids. At physiologic pH, it exists mainly as ammonium ion. Reference serum levels are less than 35 mmol/L (outside the newborn period, where higher levels are seen). Excess ammonia is excreted as urea, which is synthesized in the liver through the urea cycle. Sources of ammonia include bacterial hydrolysis of urea and other nitrogenous compounds in the intestine, the purine-nucleotide cycle and amino acid transamination in skeletal muscle, and other metabolic processes in the kidneys and liver. Increased entry of ammonia to the brain is a primary cause of neurological disorders associated with HA, such as congenital deficiencies of urea cycle enzymes, hepatic encephalopathies, Reye syndrome, several other metabolic disorders, and some toxic encepha-

On the basis of studies in animal models and other preclinical model systems, several mechanisms of ammonia neurotoxicity at the molecular level have

**182**

lopathies [26–28].

been proposed.

When ammonia is not adequately detoxified by the hepatic urea cycle, there is an increase in scavenger amino acids, including glutamine. Ammonia entering the brain is rapidly incorporated into the formation of glutamine by glutamine synthetase, present in the astrocyte. Glutamine concentrations increase in hyperammonemic states. While not measured directly, indirect measures with 1 H magnetic resonance spectroscopy (MRS) studies of patients with urea cycle disorders have demonstrated elevations of the glutamine/glutamate complex [30]. Glutamine has been implicated in hyperammonemic encephalopathy. It has been shown that a rise in plasma glutamine levels precedes HA. There is a sustained positive correlation between plasma glutamine and ammonia levels.

Inhibition of glutamine synthetase in hyperammonemic rats by treatment with enzyme inhibitors prevents the rise in cortical glutamine levels and cortical water content [31]. Clearance of synaptic glutamate by glial cells is required for the normal function of excitatory synapses and to prevent neurotoxicity. This process occurs in the atrocity, which takes up synaptic glutamate and returns glutamate to the neurons in the form of glutamine, a non-neuroactive amino acid that the neurons subsequently reconvert to glutamate via the action of mitochondrial phosphate-dependent glutaminase.

#### **2.1 Short-term clinical effects of HA**

Clinical signs of HA may occur at concentrations >60 micromol/L and are very individual as some patients may tolerate higher levels before symptoms are noticed. The short-term changes may include initially anorexia, irritability, lethargy, somnolence, disorientation, vomiting, and asterixis (flapping tremor). As symptoms progress and ammonia is not lowered, cerebral edema, coma, herniation and death [30]. In the acute stages, there is increased blood brain barrier permeability, leading to depletion of intermediates of cell energy metabolism. On an anatomic level, there is disaggregation of microtubules [29].

#### **2.2 Chronic effects of HA**

Chronic effects of HA include alterations in axonal development as well as alterations in brain amino acid and neurotransmitter levels. Electrophysiologic effects of HA include direct effects on inhibitory postsynaptic potentiation (IPSP). Neurotransmission is impacted due to increased extracellular glutamate levels and downregulation of AMPA-kainate receptors, enhanced tryptophan uptake, elevated quinolinic acid levels, and enhanced NMDA activity. Activation of NMDA receptors increases calcium in postsynaptic neurons which binds to calmodulin and activates neuronal nitric oxide (NO) synthase, increasing NO, which activates guanylate cyclase, increasing cyclic guanine monophosphate (cGMP), part of which is released to the extracellular space [31, 32]. Activation of this glutamate- NO-cGMP pathway may be involved in some forms of learning.

Recent reports indicate that guanylate cyclase and cGMP are important in learning and memory; induction of LTP is the molecular basis of some forms of learning and memory [33]. Because glial cells also have these receptors, the excessive glutamate leads to glial cell swelling, which seems to protect the neurons from excitotoxic injury. Studies in spf mouse models of OTC and other animal models of HE show neuropathological evidence of excitotoxic neuronal cell death which suggests that overactivation of NMDAR is a feature of urea cycle disorders [34] and may be age dependent [35].

**185**

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

A proportion of individuals with OTCD have a wide spectrum of neuropsychological complications including developmental delay, intellectual disability, and executive function deficits [36]. Most adult-onset patients remain asymptomatic, until they present with rapid decline in mental status and subsequently chronic

Fluctuating HA may cause delirium, confusion, and incoherent speech. In addition to subsequent regression, lack of attention leads to unemployment and introverted behavior [37]. Waisbren et al. demonstrated that nearly all asymptomatic 156 women with OTCD attained a full-scale intelligence quotient (IQ ) of 102 ± 16. Among 25 men, the full-scale IQ measured was 101 ± 21. No differences were noted between the verbal and performance scores. In addition, in 27% of females and 33% of males, working memory deficiency was observed as a constant finding. The ammonia concentration and its duration appear to be key determinants of the

Executive function (EF) is the ability to control and regulate actions and thoughts [38]. It includes processes such as working memory, self-regulation, and

Executive functions are a set of cognitive processes and competencies that control behavior and learning. It is an umbrella term which comprises neurologically based skills involving mental control and self-regulation. The general agreement of the core elements of executive functions includes inhibition, working memory, and cognitive flexibility [38, 39]. These elements are highly interrelated, and the interplay of these processes is vital in flexible, goal-directed behaviors. From the core elements of basic executive functions, higher-order executive functions such as reasoning, fluid intelligence, problem-solving, and

Historically, executive functioning has been thought to be regulated by the prefrontal cortex of the frontal lobes; however reviews found indications for the sensitivity, but not for the specificity, of executive function measures to the frontal lobe [41]. Both the frontal brain regions and other structures of the brain are

Individuals are not born with executive function skills, but rather are born with

To date, most evaluations of EF rely on parents' reports such as the Behavior Rating Inventory of Executive Function Preschool (BRIEF-P) form, which may not

EF has been previously studied using task-based functional MRI (fMRI) scans, which can be difficult to adapt for children [43]. Instead, multiple studies have relied on resting state functional MRI [44]. Reineberg et al. investigated differences in brain connectivity in relation to individual performances during different EF behavioral tasks [45]. However, to our best knowledge, resting state fMRI has not been applied to characterize EF-related brain connectivity differences in children,

the potential to develop them. With any genetic or environmental insult to the brain, the executive functions and prefrontal cortex are one of the first to suffer and suffer disproportionately. The disruption of the brain architecture can seriously

involved and necessary for successful application of these skills.

delay or impair the development of executive functioning [38].

especially at a young age (2–5 years old).

capture the development of executive skills to its full expression [42].

**3. What are the cognitive implications of HA on the brain?**

*DOI: http://dx.doi.org/10.5772/intechopen.90025*

encephalopathy [36, 37].

long-term outcome [37].

inhibitory control.

planning are built [40].

**3.1 Long-term sequelae of HA: Executive function**

#### **3. What are the cognitive implications of HA on the brain?**

A proportion of individuals with OTCD have a wide spectrum of neuropsychological complications including developmental delay, intellectual disability, and executive function deficits [36]. Most adult-onset patients remain asymptomatic, until they present with rapid decline in mental status and subsequently chronic encephalopathy [36, 37].

Fluctuating HA may cause delirium, confusion, and incoherent speech. In addition to subsequent regression, lack of attention leads to unemployment and introverted behavior [37]. Waisbren et al. demonstrated that nearly all asymptomatic 156 women with OTCD attained a full-scale intelligence quotient (IQ ) of 102 ± 16. Among 25 men, the full-scale IQ measured was 101 ± 21. No differences were noted between the verbal and performance scores. In addition, in 27% of females and 33% of males, working memory deficiency was observed as a constant finding. The ammonia concentration and its duration appear to be key determinants of the long-term outcome [37].

#### **3.1 Long-term sequelae of HA: Executive function**

Executive function (EF) is the ability to control and regulate actions and thoughts [38]. It includes processes such as working memory, self-regulation, and inhibitory control.

Executive functions are a set of cognitive processes and competencies that control behavior and learning. It is an umbrella term which comprises neurologically based skills involving mental control and self-regulation. The general agreement of the core elements of executive functions includes inhibition, working memory, and cognitive flexibility [38, 39]. These elements are highly interrelated, and the interplay of these processes is vital in flexible, goal-directed behaviors. From the core elements of basic executive functions, higher-order executive functions such as reasoning, fluid intelligence, problem-solving, and planning are built [40].

Historically, executive functioning has been thought to be regulated by the prefrontal cortex of the frontal lobes; however reviews found indications for the sensitivity, but not for the specificity, of executive function measures to the frontal lobe [41]. Both the frontal brain regions and other structures of the brain are involved and necessary for successful application of these skills.

Individuals are not born with executive function skills, but rather are born with the potential to develop them. With any genetic or environmental insult to the brain, the executive functions and prefrontal cortex are one of the first to suffer and suffer disproportionately. The disruption of the brain architecture can seriously delay or impair the development of executive functioning [38].

To date, most evaluations of EF rely on parents' reports such as the Behavior Rating Inventory of Executive Function Preschool (BRIEF-P) form, which may not capture the development of executive skills to its full expression [42].

EF has been previously studied using task-based functional MRI (fMRI) scans, which can be difficult to adapt for children [43]. Instead, multiple studies have relied on resting state functional MRI [44]. Reineberg et al. investigated differences in brain connectivity in relation to individual performances during different EF behavioral tasks [45]. However, to our best knowledge, resting state fMRI has not been applied to characterize EF-related brain connectivity differences in children, especially at a young age (2–5 years old).

*Cellular Metabolism and Related Disorders*

between plasma glutamine and ammonia levels.

phosphate-dependent glutaminase.

**2.1 Short-term clinical effects of HA**

is disaggregation of microtubules [29].

pathway may be involved in some forms of learning.

**2.2 Chronic effects of HA**

When ammonia is not adequately detoxified by the hepatic urea cycle, there is an increase in scavenger amino acids, including glutamine. Ammonia entering the brain is rapidly incorporated into the formation of glutamine by glutamine synthetase, present in the astrocyte. Glutamine concentrations increase in hyperam-

resonance spectroscopy (MRS) studies of patients with urea cycle disorders have demonstrated elevations of the glutamine/glutamate complex [30]. Glutamine has been implicated in hyperammonemic encephalopathy. It has been shown that a rise in plasma glutamine levels precedes HA. There is a sustained positive correlation

Inhibition of glutamine synthetase in hyperammonemic rats by treatment with enzyme inhibitors prevents the rise in cortical glutamine levels and cortical water content [31]. Clearance of synaptic glutamate by glial cells is required for the normal function of excitatory synapses and to prevent neurotoxicity. This process occurs in the atrocity, which takes up synaptic glutamate and returns glutamate to the neurons in the form of glutamine, a non-neuroactive amino acid that the neurons subsequently reconvert to glutamate via the action of mitochondrial

Clinical signs of HA may occur at concentrations >60 micromol/L and are very individual as some patients may tolerate higher levels before symptoms are noticed. The short-term changes may include initially anorexia, irritability, lethargy, somnolence, disorientation, vomiting, and asterixis (flapping tremor). As symptoms progress and ammonia is not lowered, cerebral edema, coma, herniation and death [30]. In the acute stages, there is increased blood brain barrier permeability, leading to depletion of intermediates of cell energy metabolism. On an anatomic level, there

Chronic effects of HA include alterations in axonal development as well as alterations in brain amino acid and neurotransmitter levels. Electrophysiologic effects of HA include direct effects on inhibitory postsynaptic potentiation (IPSP). Neurotransmission is impacted due to increased extracellular glutamate levels and downregulation of AMPA-kainate receptors, enhanced tryptophan uptake, elevated quinolinic acid levels, and enhanced NMDA activity. Activation of NMDA receptors increases calcium in postsynaptic neurons which binds to calmodulin and activates neuronal nitric oxide (NO) synthase, increasing NO, which activates guanylate cyclase, increasing cyclic guanine monophosphate (cGMP), part of which is released to the extracellular space [31, 32]. Activation of this glutamate- NO-cGMP

Recent reports indicate that guanylate cyclase and cGMP are important in learning and memory; induction of LTP is the molecular basis of some forms of learning and memory [33]. Because glial cells also have these receptors, the excessive glutamate leads to glial cell swelling, which seems to protect the neurons from excitotoxic injury. Studies in spf mouse models of OTC and other animal models of HE show neuropathological evidence of excitotoxic neuronal cell death which suggests that overactivation of NMDAR is a feature of urea cycle disorders [34] and may be age

H magnetic

monemic states. While not measured directly, indirect measures with 1

**184**

dependent [35].

#### **4. How can neuroimaging help us probe markers of neurological dysfunction in IEMs?**

Multiple studies using multimodal MRI suggest its value in the recognition of microscopic anatomic damage that *precedes clinical symptoms* in many inborn errors of metabolism and neurodegenerative disorders. Depending upon the type of imaging study, it may answer a different question regarding the pathology, biochemistry, or physiology. Neuroimaging may detect subtle abnormalities that can be correlated with neurocognitive abnormalities even in asymptomatic OTCD heterozygotes. The neuroimaging/neurocognitive studies we performed as part of the UCDC focused on adolescents and adults with OTCD. Our collective studies demonstrated that OTCD heterozygous females have changes in function of the prefrontal cortex (PFC) in association with an altered neurocognitive profile in working memory, executive functioning, and attention [46].

fMRI can allow us to understand how the brain constructs neural networks to perform cognitive tasks, probe how these networks are altered in brain disorders, and allow us to follow recovery. Magnetic resonance spectroscopy using hydrogen ( 1 H) or carbon (13C) allows us to probe both static and dynamic changes in brain metabolism [47]. The benefits of neuroimaging using MRI are the ability to view the brain in the three orthogonal views, the lack of radiation exposure, and the ability to target the organ or pathology being studied. In addition, high-performance MR hardware is available resulting in faster scans and higher resolution with higher field.

#### **4.1 Use of neuroimaging to assess brain injury in UCDs**

Neuroimaging in recent years has come to encompass many different modalities that can be combined in a single imaging session to gain complementary information regarding the brain's structural, functional, and metabolic dimensions.

A typical routine structural MRI protocol includes not only T1- and T2-weighted sequences but also, in most academic and teaching hospitals, fluid attenuation inversion recovery (FLAIR) and voxel-based morphometry (VBM) or other ability to measure tissue volume from acquired structural images on a clinical scanner. Diffusion weighted and diffusion tensor imaging (DWI and DTI) are used to study microstructural variance in WM fiber tracts [48], and proton magnetic resonance spectroscopy is used to measure brain metabolism in static and dynamic models [47]. Multimodal assessment batteries and data fusion give investigators a complex and varied perspective into the structural, functional, and biochemical parameters of the central nervous system in IEMs [49].

#### **4.2 What MRI modalities are available and what do they measure?**

#### *4.2.1 Magnetic resonance imaging (MRI)*

MRI interrogates tissue water protons via differential populations of proton spins that result when a biological sample is placed in a strong magnetic field. Using MRI, one can define brain anatomy and characterize gray matter and WM microstructural and macro-structural changes. These are read as signal abnormalities on T1- and T2-weighted images which correspond with the specific tissue pathologies. With MRI one can detect damage at a macroscopic level. One must remember that MRI findings can lag behind clinical changes and stages of disease as well as recovery processes.

**187**

time of the study.

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

Fluid-attenuated inversion recovery imaging is usually a routine part of most radiology clinical imaging sequences. Diffusion tensor imaging (DTI) is used due to its sensitivity in detecting increases in interstitial water content. Such applications include imaging brain tumors, demyelinating diseases (i.e., multiple sclerosis),

Diffusion MRI is another MRI method which allows fine mapping of the diffusion process of molecules (i.e., water) in biological tissues. DWI and DTI can be used in vivo noninvasively. DWI and DTI techniques are focused on the fact that molecular diffusion in tissues is not free but, rather, is impacted by obstacles, such as macromolecules and cell membranes (myelin). By using DTI, water molecule diffusion patterns can inform about microscopic details regarding myelin integrity

DTI relates image intensities to the relative mobility of water molecules in the tissue. It can also imply direction of the motion [48]. In general, areas that have a relatively high mean diffusion appear dark on the diffusion weighted MRI images. Diffusion MRI can also be used to make inferences about WM architecture since the

Cytotoxic edema in contrast follows sodium/potassium pump failure, often due to energy metabolism failure due to ischemic insult. It is quick and can occur within minutes of the onset of ischemia and can produce increased brain tissue water of up to 3–5%. In HA, cytotoxic edema also results. Therefore, DTI can be used in patients with UCD at baseline to assess whether patients differ with respect to WM integrity. DTI has a role in measuring functional connectivity differences between control groups and patients and to follow up patients over time to monitor disease progression, recovery, or impact of therapies [50]. It is a very good technique to also look at rapid fluxes in water content such as during a HA episode in a patient with UCD and allows follow-up noninvasively during recovery and/or with introduction of a

The most commonly used indices for the measurement of anisotropic diffusions by DTI include the relative anisotropy measure, fractional anisotropy (FA), and the volume ratio indices. These indices provide quantitative measurements of the

We have used DTI techniques together with advanced fiber tracking algorithms, to evaluate the 3D trajectories of neural tracts. This has allowed us to model WM neural connectivity in UCDs. DTI was used to determine whether there are WM microstructural abnormalities in partial OTCD that could underlie the cognitive phenotype. Our focus on WM alterations was based on prior neuropathology studies in HA. These studies have shown WM is almost exclusively affected. There is also a relationship between Gln toxicity and WM damage [51]. Anisotropy was calculated by standard methods, from the eigenvalues of the diffusion tensor by using the FA metric. After comparison between UCD patients and age-matched control groups, we established that FA of the frontal WM was significantly decreased in patients with UCD compared to the age-matched controls. This, in turn, is indicative of changes in WM microstructure (**Figure 2**). Additionally, we found an inverse relationship between FA and disease severity that was not age dependent. Based on this, we could conclude that MR imaging in OTCD may be normal in patients with late-onset disease, heterozygotes, or those not in hyperammonemic crisis at the

changes of WM integrity in brain regions that are affected by diseases.

*DOI: http://dx.doi.org/10.5772/intechopen.90025*

*4.2.2 Fluid-attenuated inversion recovery*

and architecture.

therapeutic agent.

metabolic WM disease cerebral infarcts, and gliotic scars.

*4.2.3 Diffusion weighted imaging and diffusion tensor imaging*

diffusion of water corresponds to cell geometry in axons [48].

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough? DOI: http://dx.doi.org/10.5772/intechopen.90025*

#### *4.2.2 Fluid-attenuated inversion recovery*

*Cellular Metabolism and Related Disorders*

**dysfunction in IEMs?**

attention [46].

with higher field.

( 1

**4. How can neuroimaging help us probe markers of neurological** 

Multiple studies using multimodal MRI suggest its value in the recognition of microscopic anatomic damage that *precedes clinical symptoms* in many inborn errors of metabolism and neurodegenerative disorders. Depending upon the type of imaging study, it may answer a different question regarding the pathology, biochemistry, or physiology. Neuroimaging may detect subtle abnormalities that can be correlated with neurocognitive abnormalities even in asymptomatic OTCD heterozygotes. The neuroimaging/neurocognitive studies we performed as part of the UCDC focused on adolescents and adults with OTCD. Our collective studies demonstrated that OTCD heterozygous females have changes in function of the prefrontal cortex (PFC) in association with an altered neurocognitive profile in working memory, executive functioning, and

fMRI can allow us to understand how the brain constructs neural networks to perform cognitive tasks, probe how these networks are altered in brain disorders, and allow us to follow recovery. Magnetic resonance spectroscopy using hydrogen

H) or carbon (13C) allows us to probe both static and dynamic changes in brain metabolism [47]. The benefits of neuroimaging using MRI are the ability to view the brain in the three orthogonal views, the lack of radiation exposure, and the ability to target the organ or pathology being studied. In addition, high-performance MR hardware is available resulting in faster scans and higher resolution

Neuroimaging in recent years has come to encompass many different modalities that can be combined in a single imaging session to gain complementary information regarding the brain's structural, functional, and metabolic dimensions.

A typical routine structural MRI protocol includes not only T1- and T2-weighted

sequences but also, in most academic and teaching hospitals, fluid attenuation inversion recovery (FLAIR) and voxel-based morphometry (VBM) or other ability to measure tissue volume from acquired structural images on a clinical scanner. Diffusion weighted and diffusion tensor imaging (DWI and DTI) are used to study microstructural variance in WM fiber tracts [48], and proton magnetic resonance spectroscopy is used to measure brain metabolism in static and dynamic models [47]. Multimodal assessment batteries and data fusion give investigators a complex and varied perspective into the structural, functional, and biochemical parameters

**4.2 What MRI modalities are available and what do they measure?**

MRI interrogates tissue water protons via differential populations of proton spins that result when a biological sample is placed in a strong magnetic field. Using MRI, one can define brain anatomy and characterize gray matter and WM microstructural and macro-structural changes. These are read as signal abnormalities on T1- and T2-weighted images which correspond with the specific tissue pathologies. With MRI one can detect damage at a macroscopic level. One must remember that MRI findings can lag behind clinical changes and stages of disease as well as

**4.1 Use of neuroimaging to assess brain injury in UCDs**

of the central nervous system in IEMs [49].

*4.2.1 Magnetic resonance imaging (MRI)*

**186**

recovery processes.

Fluid-attenuated inversion recovery imaging is usually a routine part of most radiology clinical imaging sequences. Diffusion tensor imaging (DTI) is used due to its sensitivity in detecting increases in interstitial water content. Such applications include imaging brain tumors, demyelinating diseases (i.e., multiple sclerosis), metabolic WM disease cerebral infarcts, and gliotic scars.

#### *4.2.3 Diffusion weighted imaging and diffusion tensor imaging*

Diffusion MRI is another MRI method which allows fine mapping of the diffusion process of molecules (i.e., water) in biological tissues. DWI and DTI can be used in vivo noninvasively. DWI and DTI techniques are focused on the fact that molecular diffusion in tissues is not free but, rather, is impacted by obstacles, such as macromolecules and cell membranes (myelin). By using DTI, water molecule diffusion patterns can inform about microscopic details regarding myelin integrity and architecture.

DTI relates image intensities to the relative mobility of water molecules in the tissue. It can also imply direction of the motion [48]. In general, areas that have a relatively high mean diffusion appear dark on the diffusion weighted MRI images. Diffusion MRI can also be used to make inferences about WM architecture since the diffusion of water corresponds to cell geometry in axons [48].

Cytotoxic edema in contrast follows sodium/potassium pump failure, often due to energy metabolism failure due to ischemic insult. It is quick and can occur within minutes of the onset of ischemia and can produce increased brain tissue water of up to 3–5%. In HA, cytotoxic edema also results. Therefore, DTI can be used in patients with UCD at baseline to assess whether patients differ with respect to WM integrity. DTI has a role in measuring functional connectivity differences between control groups and patients and to follow up patients over time to monitor disease progression, recovery, or impact of therapies [50]. It is a very good technique to also look at rapid fluxes in water content such as during a HA episode in a patient with UCD and allows follow-up noninvasively during recovery and/or with introduction of a therapeutic agent.

The most commonly used indices for the measurement of anisotropic diffusions by DTI include the relative anisotropy measure, fractional anisotropy (FA), and the volume ratio indices. These indices provide quantitative measurements of the changes of WM integrity in brain regions that are affected by diseases.

We have used DTI techniques together with advanced fiber tracking algorithms, to evaluate the 3D trajectories of neural tracts. This has allowed us to model WM neural connectivity in UCDs. DTI was used to determine whether there are WM microstructural abnormalities in partial OTCD that could underlie the cognitive phenotype. Our focus on WM alterations was based on prior neuropathology studies in HA. These studies have shown WM is almost exclusively affected. There is also a relationship between Gln toxicity and WM damage [51]. Anisotropy was calculated by standard methods, from the eigenvalues of the diffusion tensor by using the FA metric. After comparison between UCD patients and age-matched control groups, we established that FA of the frontal WM was significantly decreased in patients with UCD compared to the age-matched controls. This, in turn, is indicative of changes in WM microstructure (**Figure 2**). Additionally, we found an inverse relationship between FA and disease severity that was not age dependent. Based on this, we could conclude that MR imaging in OTCD may be normal in patients with late-onset disease, heterozygotes, or those not in hyperammonemic crisis at the time of the study.

#### **Figure 2.**

*Decreased FA in the anterior cingulate. The decrease in FA is most significant in patients with OTCD who are symptomatic, but note also FA decreased in those "asymptomatic" patients as compared to controls without any urea cycle disorder.*

DTI was much more sensitive to changes in WM microstructural differences than fast spin echo (FSE) T2-weighted imaging for detecting abnormalities in normal-appearing WM. We also found that the degree of the abnormality correlated with degree of cognitive deficits. The location of the deficits in the frontal WM is highly significant as this area is important in the connectivity of fibers vital to executive function, working memory, and attention.

#### **4.3 Progressive WM injury predicts cognitive decline with the most pronounced effects on processing speed and executive function**

With our research we have shown DTI evidence of WM injury in motor tracts that subserve executive attention and working memory and can correlate measures of FA with specific working memory tasks. These changes result from WM tract disruption and related cortical disconnection. Quantitative data on the WM microstructure provide a more direct measurement of brain tissue integrity than standard MRI sequences.

#### *4.3.1 WM damage in OTCD*

Neuropathological findings have been extensively examined in patients who have died due to urea cycle disorders. These findings shared pathology with other more common conditions such as hepatic encephalopathy as well as hypoxic ischemic encephalopathy. Previous autopsy and, more recently, neuroimaging studies suggest that OTCD results in a predilection for WM injury. And in patients several months prior to death after surviving a neonatal presentation, neuropathological findings consisting of cortical atrophy, ventriculomegaly, gliosis with Alzheimer type II astrocytes, spongiform changes at the gray/white junction, ulegyria, and spongiform changes in the deep gray nuclei-basal ganglia and thalamus have been reported in the literature [52–55].

Neuroimaging studies which have been performed several months after a neonatal hyperammonemic event, months later in neonatal coma survivors, are consistent with these pathological findings, correlating with hypomyelination of WM, myelination delay, cystic changes of the WM, and gliosis of the deep gray matter nuclei. The original reports were small case series using clinical CT initially and then, only

**189**

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

later, MRI. Survivors of prolonged hyperammonemic coma had severe anatomic abnormalities including ventriculomegaly and cortical atrophy. Today, these severe findings are rarely encountered if patients are diagnosed promptly, and duration of

The basic premise behind fMRI is the increase in blood flow to the local vasculature that accompanies neural activity in the brain. This leads to a local reduction in deoxyhemoglobin. An increase blood flow occurs without an increase of similar

Deoxyhemoglobin is paramagnetic; it alters the T2\*-weighted magnetic resonance image signal and serves as the source of the signal for fMRI [56]. Coupling between neural activity and changes in blood flow was first reported in 1890 (Roy and Sherrington) [56]. By using fMRI, one can observe how the brain is functioning and what areas of brain are activated while a person is performing a specific task. It can allow unmasking of regional vulnerability, circuitry, and recovery of function after damage or intervention.

MRS is another clinical sequence that provides noninvasive analytic method of identifying and measuring the individual brain chemicals present in various

information on brain metabolites. The major metabolites that can be seen include choline (Cho), creatine (Cr), N-acetyl aspartate (NAA), glutamine (Gln), and the osmolytes: myoinositol (mI) and taurine (Taur). Metabolites that can be detected have a unique frequency resonance that is termed the chemical shift. The chemical shift is reported as parts per million (ppm). The advantage of this measure in ppm is that it is the same at any magnetic field strength. The basis of the signal derives from Larmor frequency and coupling. The frequency of individual nuclei is compared to a reference compound called tetramethylsilane (TMS). The MRS is read from right to left. The metabolites that are disrupted in OTCD include Gln, Cho, and mI [57, 58]. One can quantitate the metabolites by either using in house software or using a commercially available program such as linear combination

The magnetic resonance (MR) signal detectable is directly proportional to the concentration of the nuclei in the prescribed voxel. Because the brain is mainly composed of water which has a concentration of 55.5 mmol per gram, this must be subtracted in the analysis as the concentration of other chemicals such as NAA or PCr is on the order of 0.015 and 0.5 mmol per gram of tissue. Common voxel sizes

Both the size and shape of a peak seen on a spectrum are due to the contribution

2.The T1 and T2 relaxation times of the metabolite. These are also affected by the TR (relaxation time) and TE (echo time) of the MRS sequence as certain

3.Magnetic inhomogeneity across the sample. This can be corrected to some extent by a process called shimming. This implies the process by which the main magnetic field (Bo) is made more homogenous by applying small electrical

metabolites at low concentration may only be seen best at low TE.

.

H–MR spectroscopy is widely used in clinical practice to provide

*DOI: http://dx.doi.org/10.5772/intechopen.90025*

**4.4 Functional MRI and UCD research (fMRI)**

hyperammonemia is shortened.

magnitude in oxygen extraction.

**4.5 Magnetic resonance spectroscopy**

brain regions. <sup>1</sup>

modeling or LCModel [59].

used in MRS are from 1 to 5 mm3

1.The concentration of nuclei.

of five attributes:

later, MRI. Survivors of prolonged hyperammonemic coma had severe anatomic abnormalities including ventriculomegaly and cortical atrophy. Today, these severe findings are rarely encountered if patients are diagnosed promptly, and duration of hyperammonemia is shortened.

#### **4.4 Functional MRI and UCD research (fMRI)**

*Cellular Metabolism and Related Disorders*

DTI was much more sensitive to changes in WM microstructural differences than fast spin echo (FSE) T2-weighted imaging for detecting abnormalities in normal-appearing WM. We also found that the degree of the abnormality correlated with degree of cognitive deficits. The location of the deficits in the frontal WM is highly significant as this area is important in the connectivity of fibers vital

*Decreased FA in the anterior cingulate. The decrease in FA is most significant in patients with OTCD who are symptomatic, but note also FA decreased in those "asymptomatic" patients as compared to controls without any* 

**4.3 Progressive WM injury predicts cognitive decline with the most pronounced** 

With our research we have shown DTI evidence of WM injury in motor tracts that subserve executive attention and working memory and can correlate measures of FA with specific working memory tasks. These changes result from WM tract disruption and related cortical disconnection. Quantitative data on the WM microstructure provide a more direct measurement of brain tissue integrity than standard

Neuropathological findings have been extensively examined in patients who have died due to urea cycle disorders. These findings shared pathology with other more common conditions such as hepatic encephalopathy as well as hypoxic ischemic encephalopathy. Previous autopsy and, more recently, neuroimaging studies suggest that OTCD results in a predilection for WM injury. And in patients several months prior to death after surviving a neonatal presentation, neuropathological findings consisting of cortical atrophy, ventriculomegaly, gliosis with Alzheimer type II astrocytes, spongiform changes at the gray/white junction, ulegyria, and spongiform changes in the deep gray nuclei-basal ganglia and thalamus have been

Neuroimaging studies which have been performed several months after a neonatal hyperammonemic event, months later in neonatal coma survivors, are consistent with these pathological findings, correlating with hypomyelination of WM, myelination delay, cystic changes of the WM, and gliosis of the deep gray matter nuclei. The original reports were small case series using clinical CT initially and then, only

to executive function, working memory, and attention.

**effects on processing speed and executive function**

**188**

MRI sequences.

**Figure 2.**

*urea cycle disorder.*

*4.3.1 WM damage in OTCD*

reported in the literature [52–55].

The basic premise behind fMRI is the increase in blood flow to the local vasculature that accompanies neural activity in the brain. This leads to a local reduction in deoxyhemoglobin. An increase blood flow occurs without an increase of similar magnitude in oxygen extraction.

Deoxyhemoglobin is paramagnetic; it alters the T2\*-weighted magnetic resonance image signal and serves as the source of the signal for fMRI [56]. Coupling between neural activity and changes in blood flow was first reported in 1890 (Roy and Sherrington) [56]. By using fMRI, one can observe how the brain is functioning and what areas of brain are activated while a person is performing a specific task. It can allow unmasking of regional vulnerability, circuitry, and recovery of function after damage or intervention.

#### **4.5 Magnetic resonance spectroscopy**

MRS is another clinical sequence that provides noninvasive analytic method of identifying and measuring the individual brain chemicals present in various brain regions. <sup>1</sup> H–MR spectroscopy is widely used in clinical practice to provide information on brain metabolites. The major metabolites that can be seen include choline (Cho), creatine (Cr), N-acetyl aspartate (NAA), glutamine (Gln), and the osmolytes: myoinositol (mI) and taurine (Taur). Metabolites that can be detected have a unique frequency resonance that is termed the chemical shift. The chemical shift is reported as parts per million (ppm). The advantage of this measure in ppm is that it is the same at any magnetic field strength. The basis of the signal derives from Larmor frequency and coupling. The frequency of individual nuclei is compared to a reference compound called tetramethylsilane (TMS). The MRS is read from right to left. The metabolites that are disrupted in OTCD include Gln, Cho, and mI [57, 58]. One can quantitate the metabolites by either using in house software or using a commercially available program such as linear combination modeling or LCModel [59].

The magnetic resonance (MR) signal detectable is directly proportional to the concentration of the nuclei in the prescribed voxel. Because the brain is mainly composed of water which has a concentration of 55.5 mmol per gram, this must be subtracted in the analysis as the concentration of other chemicals such as NAA or PCr is on the order of 0.015 and 0.5 mmol per gram of tissue. Common voxel sizes used in MRS are from 1 to 5 mm3 .

Both the size and shape of a peak seen on a spectrum are due to the contribution of five attributes:


currents. This can be done passively, as many vendors have automated shimming packages on the scanners, or manually.


Some of these principles are explained below.

MR proton spectroscopy has great utility in evaluation of brain metabolic disturbances. Although a nonspecific pattern (elevated Cho, depressed NAA) is common in many types of brain disease, short echo time (TE) MRS (i.e., TE < 30 msec) can reveal more specific metabolic signatures. It is also useful to focus on the temporal changes of chemicals rather than only what is abnormal. Furthermore, temporal changes on subsequent exams can help support or refute the benefit of ongoing therapeutic measures. A simple single voxel technique boasts better signal-to-noise ratios (SNR) and allows shorter TE options than multivoxel technique.

Voxel size is always a consideration, since there is a balance between signalto-noise ratio and tissue specificity; ideally, it should be as large as possible to achieve satisfactory SNR but small enough to target the area of interest. Generally, a 2 × 2 × 2 cm (2 cm3 ) voxel is sufficient; voxels smaller than 1 cm3 are unlikely to be worthy of the acquisition time it would require to achieve reasonable SNR. Voxel location and echo times should be selected based on the suspected and/or discovered disease patterns. We typically perform ultrashort (TE 14, TR 1500; STEAM technique), short (TE 35, TR 1500-2000; PRESS technique), and intermediate (TE 144, TR 1500-2000; PRESS) or long (TE 288, TR 1500-2000; PRESS) echo time sequences. Examples of metabolites that are best seen at short echo include glutamine and glutamate.

In the case of glycine at 3.55 ppm, it is necessary to obtain at least one MRS data point using an intermediate (i.e., 144 msec) or long (i.e., 288 msec) echo time to remove the spectral contamination of mI that is also around 3.5 ppm.

When are longer echo times preferred? Longer echo times improve diagnostic specificity in disorders such as maple syrup urine disease (MSUD) by eliminating the normal background macromolecular signal that can hide branched-chain amino and ketoacid peaks.

The noninvasive detection of elevated brain glutamine by 1 H MRS has also been shown to be a useful biomarker in chronic hepatic encephalopathy [60–62]. We have observed clinically, and it has been shown that glutamine has been implicated in hyperammonemic encephalopathy. A rise in plasma glutamine levels precedes HA [60–62]. The importance of glutamine in this process is further strengthened by the relationship between HA, neurologic dysfunction, and cerebral spinal fluid glutamine concentrations observed in patients with hepatic encephalopathy.

The UCDC presented the largest series of adult patients with OTCD who were imaged using 1 H MRS at 3 T and discuss the utility of advanced imaging in understanding the underlying mechanisms of dysfunction [57]. 1 H MRS studies have demonstrated elevations in Gln and decreases in mI and Cho in patients who are clinically symptomatic [51]. We showed with 1 H MRS decreased mI is also an important biomarker and also seen in females who describe themselves as asymptomatic [57]. We have hypothesized that the decrement of mI might constitute a useful biochemical marker with which to discriminate females with a partial deficiency.

**191**

ultimately seizures [67].

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

H MR spectroscopy is a sensitive tool to detect biochemical abnor-

malities in individual patients, in vivo 13C MR spectroscopy can reliably be used to quantitate distinct signals from glutamate and glutamine. Unambiguous assignment of these metabolites can contribute to a better understanding of the pathogenesis and treatment of brain dysfunction in UCDs. With the use of carbon 13

13C) MR spectroscopy, abnormalities in cerebral glutamate metabolism have been noted in patients with chronic hepatic encephalopathy. Therefore, the next step was to use this technique to investigate cerebral glutamate turnover rate in patients with

This method allows study of glutamate neurotransmission which is carried out by a glial neuronal process that includes the oxidation of glucose and the Gln/Glu cycle [63]. The metabolic model predicts that under conditions of elevated plasma ammonia, the increase in the rate of Gln synthesis is stoichiometrically coupled to increase in the uptake of the anaplerotic substrates CO2 and ammonia with concurrent efflux of Gln from the brain. Furthermore, studies in hyperammonemic rats suggest that only a fraction of Gln is used to synthesize GABA via Glu. The remainder passes through the neuronal TCA cycle. Bluml et al. have previously shown that there is disturbed neurotransmitter Glu/Gln cycling in chronic hepatic encephalopathy [63, 64]. In their studies, Glu enrichment was decreased and Gln

**5. Beyond ammonia: relationship of dysregulation of glutamatergic and GABAergic neurons in patients with HA and occurrence of seizures**

Despite decades of research, the mechanisms leading to neural injury in HA are still not well understood. Ammonia toxicity is not necessarily an adequate explanation for the degree of cognitive dysfunction seen in patients with argininosuccinate synthase (ASS), argininosuccinate lyase (ASL), and arginase deficiency (ARG).

Recent studies by our group and others, however, have shown that HA exposure alters several amino acid pathways and neurotransmitter systems, cerebral energy metabolism, nitric oxide synthesis, oxidative stress, and signal transduction path-

Epilepsy had previously been considered an infrequent manifestation in urea cycle disorders, but our longitudinal study (LS) of infants with UCD at a single site (Children's National Health System) found subclinical electrographic seizures (ES) (detected on EEG without clinical manifestations) to be surprisingly common

This unanticipated finding was particularly identified in neonates with HA. This new finding raises the question of whether seizures play an important role in the etiology of neurocognitive deficits in UCD and whether seizures could afford a

We have observed ES developing in patients in whom HA rebounded following discontinuation of ammonia scavengers. During HA, the brain is vulnerable to injury as a result of increased permeability and alterations in energy metabolism. In this small cohort, we observed that children with evidence of ES had abnormal MRI scans and/or adverse neurodevelopmental outcomes. This is consistent with what is seen in animal models. The animals develop change in behavior and ataxia and

*DOI: http://dx.doi.org/10.5772/intechopen.90025*

*4.5.1 13C MRS*

partial OTCD.

enrichment was increased.

ASS is also referred to as citrullinemia.

ways which all increase the risk for seizures [30, 65].

biomarker that correlates with brain damage in these disorders.

during acute hyperammonemic episodes [66].

(

Although <sup>1</sup>

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough? DOI: http://dx.doi.org/10.5772/intechopen.90025*

#### *4.5.1 13C MRS*

*Cellular Metabolism and Related Disorders*

a 2 × 2 × 2 cm (2 cm3

mine and glutamate.

and ketoacid peaks.

imaged using 1

ming packages on the scanners, or manually.

4.Another consideration, especially in the case of <sup>1</sup>

may have overlapping peaks at a certain ppm.

the chemical structure J coupling effects.

Some of these principles are explained below.

currents. This can be done passively, as many vendors have automated shim-

presence of overlapping peaks since several metabolites in whole or in part

5.Whether the line is expected to be single or a multiplet. This is determined by

MR proton spectroscopy has great utility in evaluation of brain metabolic disturbances. Although a nonspecific pattern (elevated Cho, depressed NAA) is common in many types of brain disease, short echo time (TE) MRS (i.e., TE < 30 msec) can reveal more specific metabolic signatures. It is also useful to focus on the temporal changes of chemicals rather than only what is abnormal. Furthermore, temporal changes on subsequent exams can help support or refute the benefit of ongoing therapeutic measures. A simple single voxel technique boasts better signal-to-noise

ratios (SNR) and allows shorter TE options than multivoxel technique.

remove the spectral contamination of mI that is also around 3.5 ppm.

The noninvasive detection of elevated brain glutamine by 1

standing the underlying mechanisms of dysfunction [57]. 1

clinically symptomatic [51]. We showed with 1

Voxel size is always a consideration, since there is a balance between signalto-noise ratio and tissue specificity; ideally, it should be as large as possible to achieve satisfactory SNR but small enough to target the area of interest. Generally,

) voxel is sufficient; voxels smaller than 1 cm3

In the case of glycine at 3.55 ppm, it is necessary to obtain at least one MRS data point using an intermediate (i.e., 144 msec) or long (i.e., 288 msec) echo time to

When are longer echo times preferred? Longer echo times improve diagnostic specificity in disorders such as maple syrup urine disease (MSUD) by eliminating the normal background macromolecular signal that can hide branched-chain amino

shown to be a useful biomarker in chronic hepatic encephalopathy [60–62]. We have observed clinically, and it has been shown that glutamine has been implicated in hyperammonemic encephalopathy. A rise in plasma glutamine levels precedes HA [60–62]. The importance of glutamine in this process is further strengthened by the relationship between HA, neurologic dysfunction, and cerebral spinal fluid glutamine concentrations observed in patients with hepatic encephalopathy.

The UCDC presented the largest series of adult patients with OTCD who were

demonstrated elevations in Gln and decreases in mI and Cho in patients who are

tant biomarker and also seen in females who describe themselves as asymptomatic [57]. We have hypothesized that the decrement of mI might constitute a useful biochemical marker with which to discriminate females with a partial deficiency.

H MRS at 3 T and discuss the utility of advanced imaging in under-

be worthy of the acquisition time it would require to achieve reasonable SNR. Voxel location and echo times should be selected based on the suspected and/or discovered disease patterns. We typically perform ultrashort (TE 14, TR 1500; STEAM technique), short (TE 35, TR 1500-2000; PRESS technique), and intermediate (TE 144, TR 1500-2000; PRESS) or long (TE 288, TR 1500-2000; PRESS) echo time sequences. Examples of metabolites that are best seen at short echo include gluta-

H MRS in the UCD, is the

are unlikely to

H MRS has also been

H MRS studies have

H MRS decreased mI is also an impor-

**190**

Although <sup>1</sup> H MR spectroscopy is a sensitive tool to detect biochemical abnormalities in individual patients, in vivo 13C MR spectroscopy can reliably be used to quantitate distinct signals from glutamate and glutamine. Unambiguous assignment of these metabolites can contribute to a better understanding of the pathogenesis and treatment of brain dysfunction in UCDs. With the use of carbon 13 ( 13C) MR spectroscopy, abnormalities in cerebral glutamate metabolism have been noted in patients with chronic hepatic encephalopathy. Therefore, the next step was to use this technique to investigate cerebral glutamate turnover rate in patients with partial OTCD.

This method allows study of glutamate neurotransmission which is carried out by a glial neuronal process that includes the oxidation of glucose and the Gln/Glu cycle [63]. The metabolic model predicts that under conditions of elevated plasma ammonia, the increase in the rate of Gln synthesis is stoichiometrically coupled to increase in the uptake of the anaplerotic substrates CO2 and ammonia with concurrent efflux of Gln from the brain. Furthermore, studies in hyperammonemic rats suggest that only a fraction of Gln is used to synthesize GABA via Glu. The remainder passes through the neuronal TCA cycle. Bluml et al. have previously shown that there is disturbed neurotransmitter Glu/Gln cycling in chronic hepatic encephalopathy [63, 64]. In their studies, Glu enrichment was decreased and Gln enrichment was increased.

#### **5. Beyond ammonia: relationship of dysregulation of glutamatergic and GABAergic neurons in patients with HA and occurrence of seizures**

Despite decades of research, the mechanisms leading to neural injury in HA are still not well understood. Ammonia toxicity is not necessarily an adequate explanation for the degree of cognitive dysfunction seen in patients with argininosuccinate synthase (ASS), argininosuccinate lyase (ASL), and arginase deficiency (ARG). ASS is also referred to as citrullinemia.

Recent studies by our group and others, however, have shown that HA exposure alters several amino acid pathways and neurotransmitter systems, cerebral energy metabolism, nitric oxide synthesis, oxidative stress, and signal transduction pathways which all increase the risk for seizures [30, 65].

Epilepsy had previously been considered an infrequent manifestation in urea cycle disorders, but our longitudinal study (LS) of infants with UCD at a single site (Children's National Health System) found subclinical electrographic seizures (ES) (detected on EEG without clinical manifestations) to be surprisingly common during acute hyperammonemic episodes [66].

This unanticipated finding was particularly identified in neonates with HA. This new finding raises the question of whether seizures play an important role in the etiology of neurocognitive deficits in UCD and whether seizures could afford a biomarker that correlates with brain damage in these disorders.

We have observed ES developing in patients in whom HA rebounded following discontinuation of ammonia scavengers. During HA, the brain is vulnerable to injury as a result of increased permeability and alterations in energy metabolism. In this small cohort, we observed that children with evidence of ES had abnormal MRI scans and/or adverse neurodevelopmental outcomes. This is consistent with what is seen in animal models. The animals develop change in behavior and ataxia and ultimately seizures [67].

HA episodes are critical periods in which to intervene in order to prevent long-term cognitive disability. In neonates and children, HA episodes occur in the context of a developing brain that already has vulnerabilities as a result of normal remodeling, synaptogenesis, and ion channel development. It is also the period in life recognized to be at highest risk for seizures. It is possible that seizures in HA infants and children with UCD are an early biomarker of perturbed metabolism and, left untreated, may contribute to brain injury and subsequent intellectual and other developmental disabilities.

Considerable evidence shows that HA compromises brain energy metabolism which predisposes the patient to seizures due to neuronal depolarization in association with lower energy. The seizures then in turn further lower brain energy, setting in motion a physiologic cycle: HA → lower ATP → depolarization/increased vulnerability to seizures → frank seizures (or, at least, ES) → further lowering of ATP → more seizures (or ES) [68].

#### **5.1 Seizures in UCD**

While there is a paucity of investigation of the incidence/prevalence of seizures in UCD, one early study evaluated 11 EEG tracings of 4 infants, irrespective of clinical seizure status [69]. This small study identified epileptiform EEG alterations and hypothesized that they may be a characteristic manifestation of UCD. Later, a retrospective analysis of EEG tracings and head CT scans in 49 UCD patients revealed EEG abnormalities during a clinically stable period that were predominantly observed in patients with abnormal CT scans [70].

In agreement with these reports, our group has identified that patients with distal UCD (where ammonia levels are not as elevated as in proximal disorders) have a high frequency of epilepsy and cognitive dysfunction, raising the possibility that seizures may be associated with other biochemical abnormalities in distal UCD [36, 71]. Additionally, we have shown that disrupted neural networks underlying working memory are a consistent finding in UCD patients with mild as well as severe symptoms [25, 46]. These studies strengthen the importance of understanding the incidence/prevalence of epilepsy in patients with UCDs and if and how this may affect later cognitive function. It further suggests that patients may be undertreated if we focus solely on ammonia-lowering agents and fail to recognize and treat concurrent seizures, as there are clearly other factors, such as disturbed mitochondrial function and oxidative stress, implicated in ammonia-induced neurotoxicity [68, 72–74].

#### *5.1.1 Animal models of UCD and seizures*

Both myoclonic and tonic–clonic seizures have been reported in the OTCD spf-ash mouse, an animal model of late-onset UCD with variable phenotype and severity. One study showed that the seizures were linked to the neurotoxic effect of HA on astrocytes, which increased and desynchronized astrocytic Ca2+ signaling and compromised the ability to buffer extracellular potassium. Using an animal model of inducible HA, the NAGS knockout (NAGSko) mouse, develops HA within a few hours of withdrawal of effective treatment with N-carbamylglutamate and L-citrulline (NCG + Cit) [75]. Studies in these mice demonstrated that they manifested seizures during HA but unexpectedly also had seizures during baseline recording when blood ammonia levels were normal. In this study, EEG seemed to be a sensitive measure of detecting neuronal dysfunction from HA and suggested its use as an early biomarker of its damaging effects.

**193**

**Figure 3.**

*as ammonia concentration increases further (c).*

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

The common hypothesis as to how ammonia may lead to seizures is based on the idea that reducing ammonia in the blood will reduce the influx into astrocytes, thereby inhibiting the glutamine synthetase enzyme. This is the basis of ammonia lowering agents in clinical use. However, the work of Rangroo-Thrane et al. challenged that idea by showing that this only may worsen the neurological condition

failure of buffering potassium in astrocytes actually is the critical mechanism that contributes to ammonia neurotoxicity. Using awake, intact mice that were induced to have HA, this research group reported that when ammonia was blocked from

isoform 1 (NKCC1), seizures developed. They also conclude that a therapeutic intervention should work by blocking this pathway by inhibiting NKCC1 [75]. To determine the incidence of seizures in our UCD cohorts, we conducted a data mining study of six children who were enrolled in the UCDC since 2003 and who had continuous video EEG (cVEEG) during a HA episode and sufficient data to abstract. We accessed their data including clinical information, MRI scans, and metabolic laboratory results including ammonia and glutamine levels. We found that seizures occurred in neonates with UCD even when ammonia and glutamine levels had returned to normal. We further found that interburst interval duration (the time between brain activity and silences) correlated with ammonia levels. During periods of HA, the duration of electrical silence was prolonged, and the EEG pattern could be used to predict elevated ammonia levels (**Figure 3**). A prolonged interval was also correlated with cerebral dysfunction and an abnormal follow-up MRI showing injury (**Figure 4**) [76]. cVEEG therefore can be a useful tool for managing infants with HA and may be essential for seizure management, especially for infants in deep metabolic coma. Features of the EEG appeared predictive of short-term cognitive outcome and structural injury on MRI in this cohort.

*EEG patterns change with concentration of ammonia from normal neonate (a) to increased interburst intervals, in this case also showing focal seizure (arrows) (b) to more significant suppression of brain activity* 

+

] and [K<sup>+</sup>


]. They have shown that


*DOI: http://dx.doi.org/10.5772/intechopen.90025*

by increasing neuronal exposure to both [NH4

entering the astrocyte via the potassium transporter Na<sup>+</sup>

#### *Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough? DOI: http://dx.doi.org/10.5772/intechopen.90025*

The common hypothesis as to how ammonia may lead to seizures is based on the idea that reducing ammonia in the blood will reduce the influx into astrocytes, thereby inhibiting the glutamine synthetase enzyme. This is the basis of ammonia lowering agents in clinical use. However, the work of Rangroo-Thrane et al. challenged that idea by showing that this only may worsen the neurological condition by increasing neuronal exposure to both [NH4 + ] and [K<sup>+</sup> ]. They have shown that failure of buffering potassium in astrocytes actually is the critical mechanism that contributes to ammonia neurotoxicity. Using awake, intact mice that were induced to have HA, this research group reported that when ammonia was blocked from entering the astrocyte via the potassium transporter Na<sup>+</sup> -K<sup>+</sup> -2Cl<sup>−</sup> cotransporter isoform 1 (NKCC1), seizures developed. They also conclude that a therapeutic intervention should work by blocking this pathway by inhibiting NKCC1 [75].

To determine the incidence of seizures in our UCD cohorts, we conducted a data mining study of six children who were enrolled in the UCDC since 2003 and who had continuous video EEG (cVEEG) during a HA episode and sufficient data to abstract. We accessed their data including clinical information, MRI scans, and metabolic laboratory results including ammonia and glutamine levels. We found that seizures occurred in neonates with UCD even when ammonia and glutamine levels had returned to normal. We further found that interburst interval duration (the time between brain activity and silences) correlated with ammonia levels. During periods of HA, the duration of electrical silence was prolonged, and the EEG pattern could be used to predict elevated ammonia levels (**Figure 3**). A prolonged interval was also correlated with cerebral dysfunction and an abnormal follow-up MRI showing injury (**Figure 4**) [76]. cVEEG therefore can be a useful tool for managing infants with HA and may be essential for seizure management, especially for infants in deep metabolic coma. Features of the EEG appeared predictive of short-term cognitive outcome and structural injury on MRI in this cohort.

#### **Figure 3.**

*Cellular Metabolism and Related Disorders*

other developmental disabilities.

ATP → more seizures (or ES) [68].

**5.1 Seizures in UCD**

neurotoxicity [68, 72–74].

*5.1.1 Animal models of UCD and seizures*

use as an early biomarker of its damaging effects.

HA episodes are critical periods in which to intervene in order to prevent long-term cognitive disability. In neonates and children, HA episodes occur in the context of a developing brain that already has vulnerabilities as a result of normal remodeling, synaptogenesis, and ion channel development. It is also the period in life recognized to be at highest risk for seizures. It is possible that seizures in HA infants and children with UCD are an early biomarker of perturbed metabolism and, left untreated, may contribute to brain injury and subsequent intellectual and

Considerable evidence shows that HA compromises brain energy metabolism which predisposes the patient to seizures due to neuronal depolarization in association with lower energy. The seizures then in turn further lower brain energy, setting in motion a physiologic cycle: HA → lower ATP → depolarization/increased vulnerability to seizures → frank seizures (or, at least, ES) → further lowering of

While there is a paucity of investigation of the incidence/prevalence of seizures

in UCD, one early study evaluated 11 EEG tracings of 4 infants, irrespective of clinical seizure status [69]. This small study identified epileptiform EEG alterations and hypothesized that they may be a characteristic manifestation of UCD. Later, a retrospective analysis of EEG tracings and head CT scans in 49 UCD patients revealed EEG abnormalities during a clinically stable period that were predomi-

In agreement with these reports, our group has identified that patients with distal UCD (where ammonia levels are not as elevated as in proximal disorders) have a high frequency of epilepsy and cognitive dysfunction, raising the possibility that seizures may be associated with other biochemical abnormalities in distal UCD [36, 71]. Additionally, we have shown that disrupted neural networks underlying working memory are a consistent finding in UCD patients with mild as well as severe symptoms [25, 46]. These studies strengthen the importance of understanding the incidence/prevalence of epilepsy in patients with UCDs and if and how this may affect later cognitive function. It further suggests that patients may be undertreated if we focus solely on ammonia-lowering agents and fail to recognize and treat concurrent seizures, as there are clearly other factors, such as disturbed mitochondrial function and oxidative stress, implicated in ammonia-induced

Both myoclonic and tonic–clonic seizures have been reported in the OTCD spf-ash mouse, an animal model of late-onset UCD with variable phenotype and severity. One study showed that the seizures were linked to the neurotoxic effect of HA on astrocytes, which increased and desynchronized astrocytic Ca2+ signaling and compromised the ability to buffer extracellular potassium. Using an animal model of inducible HA, the NAGS knockout (NAGSko) mouse, develops HA within a few hours of withdrawal of effective treatment with N-carbamylglutamate and L-citrulline (NCG + Cit) [75]. Studies in these mice demonstrated that they manifested seizures during HA but unexpectedly also had seizures during baseline recording when blood ammonia levels were normal. In this study, EEG seemed to be a sensitive measure of detecting neuronal dysfunction from HA and suggested its

nantly observed in patients with abnormal CT scans [70].

**192**

*EEG patterns change with concentration of ammonia from normal neonate (a) to increased interburst intervals, in this case also showing focal seizure (arrows) (b) to more significant suppression of brain activity as ammonia concentration increases further (c).*

#### **Figure 4.**

*Selected axial brain MR images at the level of the basal ganglia at day of life 14 (a–d) and 18 (e). Heterogeneous cerebral hyperperfusion improves over time between exams. (a and e) reduced diffusion is present showing hyperintense signal in the callosal splenium and genu, sagittal stratum, internal capsules, frontal WM, and, to a lesser extent (with partial pseudonormalization), the cerebral cortex and deep gray nuclei in correlation with the ADC map (not shown). (b) Hyperintensity on T1WI and (c) hypointensity onT2WI (d) are present extensively throughout most of the cerebral cortex, and mild signal changes are present affecting the cerebral deep gray nuclei. The cortical signal changes on the T1 and T1WI represent laminar necrosis. The unmyelinated cerebral WM demonstrates excessive T1 and T2 prolongation. There is mild diffuse cerebral volume loss with prominent sulci and ventricles.*

#### **6. Conclusions**

Our understanding of the neurocognitive challenges of OTCD has been improved with the study of advanced MR imaging techniques; however, many issues remain unresolved. We are beginning to understand the neural networks impacted and have been able to correlate imaging findings with specific cognitive outcomes. We now need to scale it back to determine the earliest markers of brain injury. New findings of electrographic seizures in neonates with UCD raise questions of whether seizures play an important role in the etiology of neurocognitive deficits in UCD and whether changes on the EEG could afford a biomarker that correlates with brain changes in these disorders. Future studies are directed towards

**195**

**Author details**

Andrea L. Gropman

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough?*

may inform moment to moment changes in clinical management.

studying a more diverse group of UCD patients during baseline as well as during HA events. Pattern recognition to inform the structural and biochemical changes on MRI will allow us to move towards precision management where neuromonitoring

We acknowledge grant support from NICHD, NCATS U54 HD061221, and the

We would like to thank the National Urea Cycle Foundation (NUCDF) and the

Division of Neurogenetics and Developmental Pediatrics, Neurology and Pediatrics, Children's National Medical Center, N.W. Washington, United States of America

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*Address all correspondence to: agropman@childrensnational.org

provided the original work is properly cited.

*DOI: http://dx.doi.org/10.5772/intechopen.90025*

The authors declare no conflict of interest.

families and patients who participated in our studies.

**Notes/thanks/other declarations**

**Acknowledgements**

**Conflict of interest**

O'Malley family foundation.

*Emerging Knowledge From Noninvasive Imaging Studies: Is Ammonia Control Enough? DOI: http://dx.doi.org/10.5772/intechopen.90025*

studying a more diverse group of UCD patients during baseline as well as during HA events. Pattern recognition to inform the structural and biochemical changes on MRI will allow us to move towards precision management where neuromonitoring may inform moment to moment changes in clinical management.

### **Acknowledgements**

*Cellular Metabolism and Related Disorders*

**194**

**Figure 4.**

**6. Conclusions**

*Selected axial brain MR images at the level of the basal ganglia at day of life 14 (a–d) and 18 (e). Heterogeneous cerebral hyperperfusion improves over time between exams. (a and e) reduced diffusion is present showing hyperintense signal in the callosal splenium and genu, sagittal stratum, internal capsules, frontal WM, and, to a lesser extent (with partial pseudonormalization), the cerebral cortex and deep gray nuclei in correlation with the ADC map (not shown). (b) Hyperintensity on T1WI and (c) hypointensity onT2WI (d) are present extensively throughout most of the cerebral cortex, and mild signal changes are present affecting the cerebral deep gray nuclei. The cortical signal changes on the T1 and T1WI represent laminar necrosis. The unmyelinated cerebral WM demonstrates excessive T1 and T2 prolongation. There is mild diffuse* 

Our understanding of the neurocognitive challenges of OTCD has been improved with the study of advanced MR imaging techniques; however, many issues remain unresolved. We are beginning to understand the neural networks impacted and have been able to correlate imaging findings with specific cognitive outcomes. We now need to scale it back to determine the earliest markers of brain injury. New findings of electrographic seizures in neonates with UCD raise questions of whether seizures play an important role in the etiology of neurocognitive deficits in UCD and whether changes on the EEG could afford a biomarker that correlates with brain changes in these disorders. Future studies are directed towards

*cerebral volume loss with prominent sulci and ventricles.*

We acknowledge grant support from NICHD, NCATS U54 HD061221, and the O'Malley family foundation.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Notes/thanks/other declarations**

We would like to thank the National Urea Cycle Foundation (NUCDF) and the families and patients who participated in our studies.

### **Author details**

Andrea L. Gropman Division of Neurogenetics and Developmental Pediatrics, Neurology and Pediatrics, Children's National Medical Center, N.W. Washington, United States of America

\*Address all correspondence to: agropman@childrensnational.org

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### **References**

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[2] Applegarth DA, Toone JR, Lowry RB. Incidence of inborn errors of metabolism in British Columbia, 1969- 1996. Pediatrics. 2000;**105**(1):e10

[3] Scriver CR, Sly WS, Childs B, Beaudet AL, Valle D, Kinzler KW, editors. The Metabolic and Molecular Bases of Inherited Disease. 8th ed. New York: McGraw-Hill; 1909-1964

[4] Caldovic L, Morizono H, Panglao MG, Cheng SF, Packman S, Tuchman M. Null mutations in the N-acetylglutamate synthase gene associated with acute neonatal disease and hyperammonemia. Human Genetics. 2003;**112**(4):364-368

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[6] Tuchman M, Jaleel N, Morizono H, Sheehy L, Lynch MG. Mutations and polymorphisms in the human ornithine transcarbamylase gene. Human Mutation. 2002;**19**(2):93-107

[7] Caldovic L, Abdikarim I, Narain S, Tuchman M, Morizono H. Genotypephenotype correlations in ornithine transcarbamylase deficiency: A mutation update. Journal of Genetics and Genomics. 2015;**42**(5):181-194

[8] Kang ES, Snodgrass PJ, Gerald PS. Ornithine transcarbamylase deficiency in the newborn infant. The Journal of Pediatrics. 1973;**82**(4):642-649

[9] Maestri NE, Clissold D, Brusilow SW. Neonatal onset ornithine transcarbamylase deficiency: A retrospective analysis. The Journal of Pediatrics. 1999;**134**(3):268-272

[10] McCullough BA, Yudkoff M, Batshaw ML, Wilson JM, Raper SE, Tuchman M. Genotype spectrum of ornithine transcarbamylase deficiency: Correlation with the clinical and biochemical phenotype. American Journal of Medical Genetics. 2000;**93**(4):313-319

[11] Msall M, Batshaw ML, Suss R, Brusilow SW, Mellits ED. Neurologic outcome in children with inborn errors of urea synthesis. Outcome of urea-cycle enzymopathies. The New England Journal of Medicine. 1984;**310**(23):1500-1505

[12] Msall M, Monahan PS, Chapanis N, Batshaw ML. Cognitive development in children with inborn errors of urea synthesis. Acta Paediatrica Japonica. 1988;**30**(4):435-441

[13] Campbell AG, Rosenberg LE, Snodgrass PJ, Nuzum CT. Ornithine transcarbamylase deficiency: A cause of lethal neonatal hyperammonemia in males. The New England Journal of Medicine. 1973;**288**(1):1-6

[14] Brusilow SW, Batshaw ML, Waber L. Neonatal hyperammonemic coma. Adv Pediatr. 1982;**29**:69-103

[15] Rowe PC, Newman SL, Brusilow SW. Natural history of symptomatic partial ornithine transcarbamylase deficiency. The New England Journal of Medicine. 1986;**314**(9):541-547

[16] DiMagno EP, Lowe JE, Snodgrass PJ, Jones JD. Ornithine transcarbamylase deficiency--a cause of bizarre behavior

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[25] Sprouse C, King J, Helman G, Pacheco-Colón I, Shattuck K, Breeden A, et al. Investigating neurological deficits in carriers and affected patients with ornithine transcarbamylase deficiency. Molecular Genetics and Metabolism.

[26] Dasarathy S, Mookerjee RP, Rackayova V, Rangroo Thrane V, Vairappan B, Ott P, et al. Ammonia toxicity: From head to toe? Metabolic Brain Disease. 2017;**32**(2):529-538

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[17] Nicolaides P, Liebsch D, Dale N, Leonard J, Surtees R. Neurological outcome of patients with ornithine carbamoyltransferase deficiency. Archives of Disease in Childhood. 2002;**86**(1):54-56

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[19] Batshaw ML, Brusilow S, Waber L, Blom W, Brubakk AM, Burton BK, et al. Treatment of inborn errors of urea synthesis: Activation of alternative pathways of waste nitrogen synthesis and excretion. The New England Journal of Medicine. 1982;**306**(23):1387-1392

[20] Batshaw ML, Wachtel RC, Cohen L, Starrett A, Boyd E, Perret YM, et al. Neurologic outcome in premature infants with transient asymptomatic hyperammonemia. The Journal of Pediatrics. 1986;**108**(2):271-275

[21] Christodoulou J, Qureshi IA, McInnes RR, Clarke JT. Ornithine transcarbamylase deficiency presenting with stroke like episodes. The Journal of Pediatrics. 1993;**122**(3):423-425

[22] Maestri NE, Lord C, Glynn M, Bale A, Brusilow SW. The phenotype of ostensibly healthy women who are carriers for ornithine transcarbamylase deficiency. Medicine. 1998;**77**(6):389-397

[23] Pridmore CL, Clarke JT, Blaser S. Ornithine transcarbamylase deficiency in females: An often overlooked cause of treatable encephalopathy. Journal of Child Neurology. 1995;**10**(5):369-374

[24] Yudkoff M, Daikhin Y, Nissim I, Jawad A, Wilson J, Batshaw M. In vivo nitrogen metabolism in ornithine transcarbamylase deficiency. The Journal of Clinical Investigation. 1996;**98**(9):2167-2173

[25] Sprouse C, King J, Helman G, Pacheco-Colón I, Shattuck K, Breeden A, et al. Investigating neurological deficits in carriers and affected patients with ornithine transcarbamylase deficiency. Molecular Genetics and Metabolism. 2014;**113**(1-2):136-141

[26] Dasarathy S, Mookerjee RP, Rackayova V, Rangroo Thrane V, Vairappan B, Ott P, et al. Ammonia toxicity: From head to toe? Metabolic Brain Disease. 2017;**32**(2):529-538

[27] Butterworth RF. Effects of hyperammonaemia on brain function. Journal of Inherited Metabolic Disease. 1998;**21**(Suppl 1):6-20

[28] Brusilow SW, Maestri NE. Urea cycle disorders: Diagnosis, pathophysiology, and therapy. Advances in Pediatrics. 1996;**43**:127-170

[29] Felipo V, Grau E, Miñana GS. Activation of NMDA receptor mediates the toxicity of ammonia and the effects of ammonia on the microtubuleassociated protein MAP-2. Advances in Experimental Medicine and Biology. 1993;**341**:83-93

[30] Braissant O, McLin VA, Cudalbu C. Ammonia toxicity to the brain. Journal of Inherited Metabolic Disease. 2013;**36**(4):595-612

[31] Takahashi H, Koehler RC, Brusilow SW, Traystman RJ. Inhibition of brain glutamine accumulation prevents cerebral edema in hyperammonemic rats. The American Journal of Physiology. 1991;**261** (3 Pt 2):H825-H829

**196**

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[1] Nagata N, Matsuda I, Oyanagi K. Estimated frequency of urea cycle enzymopathies in Japan. American Journal of Medical Genetics.

[9] Maestri NE, Clissold D,

transcarbamylase deficiency: A retrospective analysis. The Journal of Pediatrics. 1999;**134**(3):268-272

[10] McCullough BA, Yudkoff M, Batshaw ML, Wilson JM, Raper SE, Tuchman M. Genotype spectrum of ornithine transcarbamylase deficiency: Correlation with the clinical and biochemical phenotype. American Journal of Medical Genetics.

[11] Msall M, Batshaw ML, Suss R, Brusilow SW, Mellits ED. Neurologic outcome in children with inborn errors of urea synthesis. Outcome of urea-cycle enzymopathies. The New England Journal of Medicine.

[12] Msall M, Monahan PS, Chapanis N, Batshaw ML. Cognitive development in children with inborn errors of urea synthesis. Acta Paediatrica Japonica.

[13] Campbell AG, Rosenberg LE, Snodgrass PJ, Nuzum CT. Ornithine transcarbamylase deficiency: A cause of lethal neonatal hyperammonemia in males. The New England Journal of

Medicine. 1973;**288**(1):1-6

[15] Rowe PC, Newman SL, Brusilow SW. Natural history of symptomatic partial ornithine transcarbamylase deficiency. The New England Journal of Medicine.

[16] DiMagno EP, Lowe JE, Snodgrass PJ, Jones JD. Ornithine transcarbamylase deficiency--a cause of bizarre behavior

1986;**314**(9):541-547

[14] Brusilow SW, Batshaw ML, Waber L. Neonatal hyperammonemic coma. Adv Pediatr. 1982;**29**:69-103

2000;**93**(4):313-319

1984;**310**(23):1500-1505

1988;**30**(4):435-441

Brusilow SW. Neonatal onset ornithine

1991;**39**(2):228-229

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[75] Rangroo Thrane V, Thrane AS, Wang F, Cotrina ML, Smith NA, Chen M, et al. Ammonia triggers neuronal disinhibition and seizures by impairing astrocyte potassium buffering. Nature Medicine. 2013;**19**(12):1643-1648

[76] Wiwattanadittakul N, Prust M, Gaillard WD, Massaro A, Vezina G, Tsuchida TN, et al. The utility of EEG monitoring in neonates with hyperammonemia due to inborn errors of metabolism. Molecular Genetics and Metabolism. 2018;**125**(3):235-240

**201**

Section 9

Toxicity of Associated

Drug

### Section 9

## Toxicity of Associated Drug

*Cellular Metabolism and Related Disorders*

[62] Ross BD, Danielsen ER, Blüml S.

in forty-nine Japanese patients with urea cycle enzymopathies. American

Journal of Medical Genetics.

[71] Waisbren SE, Gropman AL, Members of the Urea Cycle Disorders Consortium (UCDC), Batshaw ML. Improving long term outcomes in urea cycle disordersreport from the urea cycle disorders consortium. Journal of Inherited Metabolic Disease. 2016;**39**(4):573-584

[72] Norenberg M. Oxidative and nitrosative stress in ammonia neurotoxicity. Hepatology.

[73] Felipo V, Butterworth RF. Mitochondrial dysfunction in acute hyperammonemia. Neurochemistry International. 2002;**40**:487-491

of ammonia and fatty acids:

Neurochemical Research.

1991;**16**:795-803

[74] Lai JCK, Cooper AJL. Neurotoxicity

Differential inhibition of mitochondrial dehydrogenases by ammonia and fatty acyl coenzyme a derivatives.

[75] Rangroo Thrane V, Thrane AS, Wang F, Cotrina ML, Smith NA, Chen M, et al. Ammonia triggers neuronal disinhibition and seizures by impairing astrocyte potassium buffering. Nature Medicine. 2013;**19**(12):1643-1648

[76] Wiwattanadittakul N, Prust M, Gaillard WD, Massaro A, Vezina G, Tsuchida TN, et al. The utility of EEG monitoring in neonates with hyperammonemia due to inborn errors of metabolism. Molecular Genetics and Metabolism. 2018;**125**(3):235-240

1991;**40**(4):477-481

2003;**37**:245-248

spectroscopy: The new gold standard for diagnosis of clinical and subclinical hepatic encephalopathy? Digestive Diseases. 1996;**14**(Suppl 1):30-39

[63] Westergaard N, Sonnewald U, Schousboe A. Metabolic trafficking between neurons and astrocytes: The glutamate/glutamine cycle revisited. Developmental Neuroscience.

[64] Blüml S, Moreno-Torres A, Ross BD. [1-13C] glucose MRS in chronic hepatic encephalopathy in man. Magnetic Resonance in Medicine.

[65] Cagnon L, Braissant O.

Hyperammonemia-induced toxicity for the developing central nervous system. Brain Research Reviews.

[66] Wiwattanadittakul N, Prust M, Gaillard WD, et al. The utility of EEG monitoring in neonates with hyperammonemia due to inborn errors of metabolism. Molecular Genetics and Metabolism. 2018 Nov;**125**(3):235-240

[67] Jang Y, Smith NA, Liu J, et al. Neurological defects in the animal model of inducible hyperammonemia. Molecular Genetics and Metabolism.

[68] Bosoi CR, Rose CF. Identifying the direct effects of ammonia on the brain. Metabolic Brain Disease. 2008;**24**:95-102

Kooi KA. Electroencephalographic findings in urea-cycle disorders. Electroencephalography and Clinical Neurophysiology. 1984;**57**(2):105-112

[70] Nagata N, Matsuda I, Matsuura T, Oyanagi K, Tada K, Narisawa K, et al. Retrospective survey of urea cycle disorders: Part 2. Neurological outcome

Proton magnetic resonance

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**200**

**203**

the withdrawal of the culprit drug [9].

**Chapter 12**

*Ágnes Kinyó*

gliptins, eosinophil

**1. Introduction**

**Abstract**

Dipeptidyl Peptidase-4 Inhibitor-

Bullous pemphigoid (BP) is the most common type of autoimmune bullous diseases; drug-induced bullous pemphigoid is a rare variant of it. In the last decade, there is an increasing prevalence of BP, especially dipeptidyl peptidase-4 inhibitorassociated BP (DPP-4i-BP), with the higher prevalence of BP in diabetic patients. Recently, several clinical phenotypes of BP were detected, but there is a tendency in BP cases related to DPP-4 inhibitors to show an atypical noninflammatory form with less distributed skin symptoms, mild erythema, decreased eosinophilic infiltration in the periblister area, and normal or slightly elevated peripheral eosinophil count. Anti-NC16A BP180 autoantibodies are less frequently detected by ELISA, but they response to other epitopes of BP180. Clinical outcome is similar such as in classical non-DPP-4 BP patients, regardless of withdrawal of DPP-4 inhibitors.

**Keywords:** bullous pemphigoid, noninflammatory, dipeptidyl peptidase-4 inhibitor,

Bullous pemphigoid (BP) is a rare autoimmune blistering disease of elderly patients, but in the last decades, it shows increasing incidence [1–8]. Higher prevalence of BP may be according to the increasing global life expectancy of the population, increasing incidence of predisposing neurological diseases, growing numbers of provoking drugs, and improving awareness of newly recognized atypical clinical phenotypes and better diagnostic methods [1]. The role of culprit drugs such as neuroleptics, diuretics, and antidiabetics is reported in several studies [1, 2, 9]. BP is typically present in elderly with a higher predominance in female patients [4, 7]. The classical clinical features of BP are generalized bullous skin eruptions with surrounding erythema and itching; peripheral eosinophilia is also common. Mucosal involvement was observed in 10–30% of patients [2]. Atypical clinical variants may be present up to 20% in BP, including the more common prurigo-like or urticarial type, eczema-like type, dyshidrosiform type, erosive type, and erythema annulare centrifugum-like phenotype [1, 7]. The diagnosis is based on the histological findings, including direct and indirect immunofluorescence microscopy and anti-BP180/BP230 enzyme-linked immunosorbent assays (ELISA) [2]. The gold standard for the treatment of the disease according to guidelines is corticosteroid, in topical or systemic administration and in severe cases with adjuvant immunosuppressive medications, such as azathioprine, methotrexate, or mycophenolate mofetil [2]. In the case of drug-induced BP, the most important therapeutic step is

Associated Bullous Pemphigoid

#### **Chapter 12**

## Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid

*Ágnes Kinyó*

#### **Abstract**

Bullous pemphigoid (BP) is the most common type of autoimmune bullous diseases; drug-induced bullous pemphigoid is a rare variant of it. In the last decade, there is an increasing prevalence of BP, especially dipeptidyl peptidase-4 inhibitorassociated BP (DPP-4i-BP), with the higher prevalence of BP in diabetic patients. Recently, several clinical phenotypes of BP were detected, but there is a tendency in BP cases related to DPP-4 inhibitors to show an atypical noninflammatory form with less distributed skin symptoms, mild erythema, decreased eosinophilic infiltration in the periblister area, and normal or slightly elevated peripheral eosinophil count. Anti-NC16A BP180 autoantibodies are less frequently detected by ELISA, but they response to other epitopes of BP180. Clinical outcome is similar such as in classical non-DPP-4 BP patients, regardless of withdrawal of DPP-4 inhibitors.

**Keywords:** bullous pemphigoid, noninflammatory, dipeptidyl peptidase-4 inhibitor, gliptins, eosinophil

#### **1. Introduction**

Bullous pemphigoid (BP) is a rare autoimmune blistering disease of elderly patients, but in the last decades, it shows increasing incidence [1–8]. Higher prevalence of BP may be according to the increasing global life expectancy of the population, increasing incidence of predisposing neurological diseases, growing numbers of provoking drugs, and improving awareness of newly recognized atypical clinical phenotypes and better diagnostic methods [1]. The role of culprit drugs such as neuroleptics, diuretics, and antidiabetics is reported in several studies [1, 2, 9]. BP is typically present in elderly with a higher predominance in female patients [4, 7]. The classical clinical features of BP are generalized bullous skin eruptions with surrounding erythema and itching; peripheral eosinophilia is also common. Mucosal involvement was observed in 10–30% of patients [2]. Atypical clinical variants may be present up to 20% in BP, including the more common prurigo-like or urticarial type, eczema-like type, dyshidrosiform type, erosive type, and erythema annulare centrifugum-like phenotype [1, 7]. The diagnosis is based on the histological findings, including direct and indirect immunofluorescence microscopy and anti-BP180/BP230 enzyme-linked immunosorbent assays (ELISA) [2]. The gold standard for the treatment of the disease according to guidelines is corticosteroid, in topical or systemic administration and in severe cases with adjuvant immunosuppressive medications, such as azathioprine, methotrexate, or mycophenolate mofetil [2]. In the case of drug-induced BP, the most important therapeutic step is the withdrawal of the culprit drug [9].

#### **2. Bullous pemphigoid and diabetes**

BP is a chronic, relapsing disease in patients with several comorbidities and significant morbidity. Investigating the prevalence of diabetes mellitus (DM) in BP, a higher frequency of DM has been found in the last decade [10, 11]. In accordance to several case reports [12–18], case series, case-control studies, pharmacovigilance reports, and retrospective investigations [19–37], the growing number of DM in BP patients is in association with the increasing use of an antidiabetic drug, the dipeptidyl peptidase-4 inhibitor (DPP-4i). DPP-4i, also called gliptins, was approved in 2006 to treat type 2 DM. Sitagliptin, vildagliptin, linagliptin, saxagliptin, and alogliptin have been approved by FDA or EMA; anagliptin, trelagliptin, omarigliptin, and teneligliptin have approval only in Japan. Gliptins are used in monotherapy or in combination with metformin. However, there is a clear evidence of provoking role of DPP-4 inhibitors in BP; the pathomechanism of it is still not understood.

#### **3. Demographics of DPP-4 inhibitor-related BP**

DPP-4 inhibitor intake was associated with a threefold increased risk for BP [27, 31, 38]. According to the former investigations [14, 23, 26, 27, 29, 31, 38, 39], vildagliptin has the strongest association with BP; the risk was tenfold (ranged between 7.23 and 11.8) in a systemic review and meta-analysis by Kridin et al. [38]. A higher, sixfold risk was also observed with linagliptin [27, 38]. Higher risk of DPP-4i-BP was also found with sitagliptin by Lee et al. [40], and they also found in a larger sample size (patients with DPP-4i-BP n = 260) that the risks associated with specific DPP-4 inhibitors were lower than the previous studies [27, 38], 1.81 for vildagliptin, 1.64 for linagliptin, and 1.7 for sitagliptin. However, a significant association was detected with vildagliptin, linagliptin, and sitagliptin in age- and sex-matched controlled population; the association with saxagliptin in BP was not significant [27, 31]. Saxagliptin, anagliptin- and alogliptin-induced BP were presented only in a few sporadic cases [29, 31, 32, 40, 41]. DPP-4 inhibitors are often given in combination with metformin; the two recent publications reported that the association of BP and gliptins is independent of metformin exposure [27, 30]. Despite the BP is more common in females, a multicenter investigation and EudraVigilance data showed that DPP-4 inhibitor-associated BP tends to be more common in men [14, 23], similarly to Kridin et al. [27] and Lee et al. [40] and in contrast to Varpuluoma et al., who found a higher risk for BP in women taking DPP-4 inhibitors [30]. The mean age of DPP-4i-related BP patients ranged between 76.6 and 79.1 years [23, 27, 39]. Kridin et al. presented the strongest association in patients younger than 70 years [27], while Benzaquen et al. found stronger association in patients older than 80 years [23], while Lee et al. observed 1.76-fold risk in patients younger than 75 years and 1.5-fold risk in patients older than 75 years [40]. The mean latency period between the initiation of gliptin and the appearance of BP is ranging from 6 to 26.4 months [23, 27, 29, 30, 33]. That means DPP-4 inhibitors can be suspected in the pathogenesis of BP if the drug has been initiated at least 6 months, but it also has to be considered if the drug intake last for more than 2 years prior to the onset of BP.

#### **4. Clinical features of DPP-4 inhibitors-related noninflammatory BP**

The classical clinical picture of BP is generalized as bullous skin lesions, tense blisters with severe urticarial erythema. Recent publications characterized a noninflammatory form of BP with limited distribution, smaller blisters, and scant erythema

**205**

**Figure 2.**

*erythema on the upper extremities.*

**Figure 1.**

(**Figures 1** and **2**) [37, 42, 43]. These noninflammatory phenotypes do not react with the NC16A domain of BP, show better clinical outcome, and has a higher prevalence in DPP-4 inhibitor taking patients [22, 32, 34–37, 42, 43]. Noninflammatory BP can

*DPP-4i-related bullous pemphigoid in a female patient with small, round erosions without* 

*DPP-4i-related bullous pemphigoid. Mild skin involvement localized to the upper part of the trunk with small* 

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid*

*DOI: http://dx.doi.org/10.5772/intechopen.84933*

*blisters and erosions without erythema in a male patient.*

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid DOI: http://dx.doi.org/10.5772/intechopen.84933*

#### **Figure 1.**

*Cellular Metabolism and Related Disorders*

**2. Bullous pemphigoid and diabetes**

**3. Demographics of DPP-4 inhibitor-related BP**

BP is a chronic, relapsing disease in patients with several comorbidities and significant morbidity. Investigating the prevalence of diabetes mellitus (DM) in BP, a higher frequency of DM has been found in the last decade [10, 11]. In accordance to several case reports [12–18], case series, case-control studies, pharmacovigilance reports, and retrospective investigations [19–37], the growing number of DM in BP patients is in association with the increasing use of an antidiabetic drug, the dipeptidyl peptidase-4 inhibitor (DPP-4i). DPP-4i, also called gliptins, was approved in 2006 to treat type 2 DM. Sitagliptin, vildagliptin, linagliptin, saxagliptin, and alogliptin have been approved by FDA or EMA; anagliptin, trelagliptin, omarigliptin, and teneligliptin have approval only in Japan. Gliptins are used in monotherapy or in combination with metformin. However, there is a clear evidence of provoking role of DPP-4 inhibitors in BP; the pathomechanism of it is still not understood.

DPP-4 inhibitor intake was associated with a threefold increased risk for BP [27, 31, 38]. According to the former investigations [14, 23, 26, 27, 29, 31, 38, 39], vildagliptin has the strongest association with BP; the risk was tenfold (ranged between 7.23 and 11.8) in a systemic review and meta-analysis by Kridin et al. [38]. A higher, sixfold risk was also observed with linagliptin [27, 38]. Higher risk of DPP-4i-BP was also found with sitagliptin by Lee et al. [40], and they also found in a larger sample size (patients with DPP-4i-BP n = 260) that the risks associated with specific DPP-4 inhibitors were lower than the previous studies [27, 38], 1.81 for vildagliptin, 1.64 for linagliptin, and 1.7 for sitagliptin. However, a significant association was detected with vildagliptin, linagliptin, and sitagliptin in age- and sex-matched controlled population; the association with saxagliptin in BP was not significant [27, 31]. Saxagliptin, anagliptin- and alogliptin-induced BP were presented only in a few sporadic cases [29, 31, 32, 40, 41]. DPP-4 inhibitors are often given in combination with metformin; the two recent publications reported that the association of BP and gliptins is independent of metformin exposure [27, 30]. Despite the BP is more common in females, a multicenter investigation and EudraVigilance data showed that DPP-4 inhibitor-associated BP tends to be more common in men [14, 23], similarly to Kridin et al. [27] and Lee et al. [40] and in contrast to Varpuluoma et al., who found a higher risk for BP in women taking DPP-4 inhibitors [30]. The mean age of DPP-4i-related BP patients ranged between 76.6 and 79.1 years [23, 27, 39]. Kridin et al. presented the strongest association in patients younger than 70 years [27], while Benzaquen et al. found stronger association in patients older than 80 years [23], while Lee et al. observed 1.76-fold risk in patients younger than 75 years and 1.5-fold risk in patients older than 75 years [40]. The mean latency period between the initiation of gliptin and the appearance of BP is ranging from 6 to 26.4 months [23, 27, 29, 30, 33]. That means DPP-4 inhibitors can be suspected in the pathogenesis of BP if the drug has been initiated at least 6 months, but it also has to be considered if the drug intake last for more than 2 years prior to the

**4. Clinical features of DPP-4 inhibitors-related noninflammatory BP**

The classical clinical picture of BP is generalized as bullous skin lesions, tense blisters with severe urticarial erythema. Recent publications characterized a noninflammatory form of BP with limited distribution, smaller blisters, and scant erythema

**204**

onset of BP.

*DPP-4i-related bullous pemphigoid. Mild skin involvement localized to the upper part of the trunk with small blisters and erosions without erythema in a male patient.*

#### **Figure 2.**

*DPP-4i-related bullous pemphigoid in a female patient with small, round erosions without erythema on the upper extremities.*

(**Figures 1** and **2**) [37, 42, 43]. These noninflammatory phenotypes do not react with the NC16A domain of BP, show better clinical outcome, and has a higher prevalence in DPP-4 inhibitor taking patients [22, 32, 34–37, 42, 43]. Noninflammatory BP can

also be found in non-DPP-4-related cases but in a significantly lower manner. Higher frequency of mucosal involvement was reported in gliptin-associated BP in two studies (Kridin et al., 22.2%, n = 36, and Chijiwa et al., 78%, n = 9) [27, 33], but this observation was not supported by Plaquevent (n = 108) [31]. Interestingly, in gliptinassociated mucous membrane pemphigoid (MMP) there is a significantly lower buccal and more common cutaneous involvement [44]. Previous studies demonstrated that eosinophil count is in correlation with the severity of BP [45–47] and with BPDAI score [46]. Comparing the Bullous Pemphigoid Disease Area Index (BPDAI) [48], BPDAI scores for urticaria/erythema (U/E) were significantly lower in noninflammatory phenotypes [33, 36, 42, 43], and lower BPDAI U/E was in correlation with decreased eosinophil count in the perilesional skin [33, 42]. Significantly decreased peripheral eosinophil count was detected in patients of Kridin et al. [27].

#### **5. Immunological characterization of DPP-4 inhibitor-related BP**

In BP, there are two targets for autoantibodies, the hemidesmosomal BP180 and BP230 and the juxtamembranous extracellular non-collagenous 16A (NC16A), both of them can be easily detected by commercially available ELISA tests [2, 49, 50]. The domain of BP180 (also called COL17) is a major target epitope in 80–90% of cases [49]. In several investigations, noninflammatory BP patients did not show reactivity against the NC16A domain of BP180, but they were positive for full-length BP180 and its ectodomain midportion with ELISA [34, 36, 42]. The midportion of BP180 is more likely to be recognized than the NC16A domain in DPP-4i-associated noninflammatory BP patients; they are presented with localized symptoms and mild erythema [32, 35, 36, 42, 51]. Although there was a positive reaction to anti-NC16A in DPP-4i-BP cases, but they were mainly presented with prominent erythema and inflammation, concurring with classical phenotype of BP [31, 35, 42]. Kawaguchi et al. showed that the rate of ELISA positivity and antibody titers for anti-BP180 NC16A was significantly lower in DPP-4i-BP than the non-DPP-4 group [22], and this lower titer was also observed by García-Díez et al. [52]. Kawaguchi has also emphasized that patients with DPP-4i-BP tended to have noninflammatory phenotype of BP and presented with negative ELISA for BP180 NC16A domain [22]. Some studies reported noninflammatory DPP-4-induced BP patients who were negative for anti-NC16A domain initially but responded to the full-length BP180 and became positive for NC16A during the course of the disease. This epitope spreading was observed in several cases, after the prolonged use of DPP-4 inhibitors after the onset of BP [17, 37, 52]. Other investigations also demonstrated that multiple epitopes of BP180 are targeted in DPP-4i-BP (midportion, C terminus, and LAD1) [35, 52], and it may suggest that epitope spreading is more common in DPP-4i-BP than in classical BP cases [35]. García-Díez et al. suggested the major role of the midportion of BP180 in DPP-4i-BP, while other BP180 regions are involved later by epitope spreading [52]. Indirect IF positivity was also detected in DPP-4i-BP patients [13, 27, 34], and anti-BP230 autoantibodies were present [34, 35], but the sensitivity of the test was only 38%, which is lower than usually reported [51].

#### **6. Clinical outcome**

Based on several investigations, withdrawal of the DPP-4 inhibitors was the first therapeutic step in most cases in the treatment of the disease [23, 34]. Regarding to these data, discontinuation of DPP-4i treatment seems to have a favorable

**207**

**Table 1.**

*Comparison of clinical features in DPP-4i-related and classical type bullous pemphigoid.*

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid*

4i-BP patients such it was previously reported [31].

**7. Conclusions**

impact on the clinical outcome of BP [23, 27, 34], but Plaquevent et al. have found that there is no difference in outcome in patients who have further got the gliptin treatment after the diagnosis of BP [31]. Regardless of DPP-4 inhibitor withdrawal, standard treatment protocol was applied in most cases, topical potent corticosteroid treatment in localized form and gold standard systemic corticosteroid treatment with adjuvant immunosuppressive therapy, such as azathioprine, mycophenolate mofetil, or methotrexate in severe cases [27, 31]. Relapse rates were similar in DPP-

Dipeptidyl peptidase-4 inhibitors (also called gliptins) are widely used drug in the treatment of type 2 diabetes mellitus. There is an increased risk of BP in patients during DPP-4 inhibitor treatment. The exact pathomechanism of DPP-4i-associated BP is still unclear. Dipeptidyl peptidase 4 (also called CD26) is a 110kDa transmembrane glycoprotein, which is expressed on the surface of several cells, such as T cells [53, 54]. DPP-4 has antihyperglycemic effect and enzymatic activity; it plays a major role in glucose metabolism by blocking incretin [54]. DPP-4 is a plasminogen receptor that activates plasminogen resulted in plasmin formation [55, 56]. Plasmin, a serine protease, which has a high level in lesional skin and in blister fluid in BP [57], cleaves BP180 within the NC16A domain [58]. Cleavage of BP180 in the NC16A region can induce neoepitopes with altered antigenicities [42, 59]. The antifibrotic effect of DPP-4 inhibitors in the skin also supports the role of DPP-4 in collagen metabolism [56]. DPP-4 is involved in immune cell activation, and its inhibition can modify the immune response, which may increase the activation of eosinophil recruitment into the dermis, which is considered to be essential in blister formation in BP [60]. In contrary to these findings, in patients with gliptin-associated noninflammatory BP, both peripheral and perilesional skin eosinophil counts are significantly lower than in classical BP [27, 33], so the exact pathognostic role of eosinophils in DPP-4-related BP needs further investigations. It is also not elucidated why vildagliptin has the strongest association with BP, but it is known that vildagliptin has the lowest selectivity among gliptins with strong inhibition of DDP8 and DPP9 isozymes [22, 61]. Some results suggest that DPP-4 inhibitor has immunomodifier effect mainly in

*DOI: http://dx.doi.org/10.5772/intechopen.84933*

impact on the clinical outcome of BP [23, 27, 34], but Plaquevent et al. have found that there is no difference in outcome in patients who have further got the gliptin treatment after the diagnosis of BP [31]. Regardless of DPP-4 inhibitor withdrawal, standard treatment protocol was applied in most cases, topical potent corticosteroid treatment in localized form and gold standard systemic corticosteroid treatment with adjuvant immunosuppressive therapy, such as azathioprine, mycophenolate mofetil, or methotrexate in severe cases [27, 31]. Relapse rates were similar in DPP-4i-BP patients such it was previously reported [31].

#### **7. Conclusions**

*Cellular Metabolism and Related Disorders*

also be found in non-DPP-4-related cases but in a significantly lower manner. Higher frequency of mucosal involvement was reported in gliptin-associated BP in two studies (Kridin et al., 22.2%, n = 36, and Chijiwa et al., 78%, n = 9) [27, 33], but this observation was not supported by Plaquevent (n = 108) [31]. Interestingly, in gliptinassociated mucous membrane pemphigoid (MMP) there is a significantly lower buccal and more common cutaneous involvement [44]. Previous studies demonstrated that eosinophil count is in correlation with the severity of BP [45–47] and with BPDAI score [46]. Comparing the Bullous Pemphigoid Disease Area Index (BPDAI) [48], BPDAI scores for urticaria/erythema (U/E) were significantly lower in noninflammatory phenotypes [33, 36, 42, 43], and lower BPDAI U/E was in correlation with decreased eosinophil count in the perilesional skin [33, 42]. Significantly decreased

peripheral eosinophil count was detected in patients of Kridin et al. [27].

**5. Immunological characterization of DPP-4 inhibitor-related BP**

and BP230 and the juxtamembranous extracellular non-collagenous 16A (NC16A), both of them can be easily detected by commercially available ELISA tests [2, 49, 50]. The domain of BP180 (also called COL17) is a major target epitope in 80–90% of cases [49]. In several investigations, noninflammatory BP patients did not show reactivity against the NC16A domain of BP180, but they were positive for full-length BP180 and its ectodomain midportion with ELISA [34, 36, 42]. The midportion of BP180 is more likely to be recognized than the NC16A domain in DPP-4i-associated noninflammatory BP patients; they are presented with localized symptoms and mild erythema [32, 35, 36, 42, 51]. Although there was a positive reaction to anti-NC16A in DPP-4i-BP cases, but they were mainly presented with prominent erythema and inflammation, concurring with classical phenotype of BP [31, 35, 42]. Kawaguchi et al. showed that the rate of ELISA positivity and antibody titers for anti-BP180 NC16A was significantly lower in DPP-4i-BP than the non-DPP-4 group [22], and this lower titer was also observed by García-Díez et al. [52]. Kawaguchi has also emphasized that patients with DPP-4i-BP tended to have noninflammatory phenotype of BP and presented with negative ELISA for BP180 NC16A domain [22]. Some studies reported noninflammatory DPP-4-induced BP patients who were negative for anti-NC16A domain initially but responded to the full-length BP180 and became positive for NC16A during the course of the disease. This epitope spreading was observed in several cases, after the prolonged use of DPP-4 inhibitors after the onset of BP [17, 37, 52]. Other investigations also demonstrated that multiple epitopes of BP180 are targeted in DPP-4i-BP (midportion, C terminus, and LAD1) [35, 52], and it may suggest that epitope spreading is more common in DPP-4i-BP than in classical BP cases [35]. García-Díez et al. suggested the major role of the midportion of BP180 in DPP-4i-BP, while other BP180 regions are involved later by epitope spreading [52]. Indirect IF positivity was also detected in DPP-4i-BP patients [13, 27, 34], and anti-BP230 autoantibodies were present [34, 35], but the sensitivity of the test was only 38%, which is lower than usually reported [51].

In BP, there are two targets for autoantibodies, the hemidesmosomal BP180

Based on several investigations, withdrawal of the DPP-4 inhibitors was the first therapeutic step in most cases in the treatment of the disease [23, 34]. Regarding to these data, discontinuation of DPP-4i treatment seems to have a favorable

**206**

**6. Clinical outcome**

Dipeptidyl peptidase-4 inhibitors (also called gliptins) are widely used drug in the treatment of type 2 diabetes mellitus. There is an increased risk of BP in patients during DPP-4 inhibitor treatment. The exact pathomechanism of DPP-4i-associated BP is still unclear. Dipeptidyl peptidase 4 (also called CD26) is a 110kDa transmembrane glycoprotein, which is expressed on the surface of several cells, such as T cells [53, 54]. DPP-4 has antihyperglycemic effect and enzymatic activity; it plays a major role in glucose metabolism by blocking incretin [54]. DPP-4 is a plasminogen receptor that activates plasminogen resulted in plasmin formation [55, 56]. Plasmin, a serine protease, which has a high level in lesional skin and in blister fluid in BP [57], cleaves BP180 within the NC16A domain [58]. Cleavage of BP180 in the NC16A region can induce neoepitopes with altered antigenicities [42, 59]. The antifibrotic effect of DPP-4 inhibitors in the skin also supports the role of DPP-4 in collagen metabolism [56]. DPP-4 is involved in immune cell activation, and its inhibition can modify the immune response, which may increase the activation of eosinophil recruitment into the dermis, which is considered to be essential in blister formation in BP [60]. In contrary to these findings, in patients with gliptin-associated noninflammatory BP, both peripheral and perilesional skin eosinophil counts are significantly lower than in classical BP [27, 33], so the exact pathognostic role of eosinophils in DPP-4-related BP needs further investigations. It is also not elucidated why vildagliptin has the strongest association with BP, but it is known that vildagliptin has the lowest selectivity among gliptins with strong inhibition of DDP8 and DPP9 isozymes [22, 61]. Some results suggest that DPP-4 inhibitor has immunomodifier effect mainly in



genetically susceptible individuals, and they have detected that HLA-DQB1\*03:01 allele has higher prevalence in DPP-4i-BP patients [22, 62].

In conclusion, DPP-4 inhibitor-related BP tends to be presented with noninflammatory phenotype of BP, with limited extension, smaller blisters, scant perilesional erythema and eosinophilic infiltration, and normal or slightly elevated peripheral eosinophil count (**Table 1**). Anti-NC16A BP180 positivity is less common, and ELISA titers are slightly elevated, similarly to anti-BP230, but positivity for full-length BP180 or other epitopes of BP180 may be detected. Response to therapy is similar such as in classical non-DPP-4i-BP patients, regardless of withdrawal of DPP-4 inhibitors.

### **Conflict of interest**

There is no conflict of interest.

#### **Acronyms and abbreviations**


### **Author details**

#### Ágnes Kinyó

Department of Dermatology, Venereology and Oncodermatology, University of Pécs, Pécs, Hungary

\*Address all correspondence to: kinyo.agnes@pte.hu

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**209**

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid*

Journal of Investigative Dermatology. 2012;**132**:1998-2004. DOI: 10.1038/

[8] Försti AK, Jokelainen J, Timonen M, Tasanen K. Increasing incidence of bullous pemphigoid in Northern Finland: A retrospective database study in Oulu University Hospital. The British Journal of Dermatology. 2014;**171**: 1223-1226. DOI: 10.1111/bjd.13189

[9] Stavropoulos PG, Soura E, Antoniou C. Drug-induced pemphigoid: A review of the literature. Journal of the

European Academy of Dermatology and Venereology. 2014;**28**:1133-1140. DOI:

[10] Fania L, Di Zenzo G, Didona B, Pilla MA, Sobrino L, Panebianco A, et al. Increased prevalence of diabetes mellitus in bullous pemphigoid patients during the last decade. Journal of the European Academy of Dermatology and Venereology. 2018;**32**:e153-e154. DOI:

[11] Gravani A, Gaitanis G, Tsironi T, Tigas S, Bassukas ID. Changing prevalence of diabetes mellitus in bullous pemphigoid: It is the dipeptidyl peptidase-4 inhibitors. Journal of the European Academy of Dermatology and Venereology. 2018;**32**:e438-e439. DOI:

[12] Aouidad I, Fite C, Marinho E, Deschamps L, Crickx B, Descamps V. A case report of bullous pemphigoid induced by dipeptidyl peptidase-4 inhibitors. JAMA Dermatology. 2013;**149**:243-245. DOI: 10.1001/

jid.2012.35

10.1111/jdv.12366

10.1111/jdv.14649

10.1111/jdv.14957

jamadermatol.2013.1073

[13] Attaway A, Mersfelder TL, Vaishnav S, Baker JK. Bullous

peptidase IV inhibitors. A case report and review of literature. Journal of Dermatological Case

pemphigoid associated with dipeptidyl

*DOI: http://dx.doi.org/10.5772/intechopen.84933*

Pemphigoid: Overview and potential explanations. Frontiers in Medicine (Lausanne). 2018;**5**:220. DOI: 10.3389/

[2] Bernard P, Antonicelli F. Bullous pemphigoid: A review of its diagnosis, associations and treatment. American Journal of Clinical Dermatology. 2017;**18**:513-528. DOI: 10.1007/

[3] Schmidt E, Spindler V, Eming R, Amagai M, Antonicelli F, Baines JF, et al. Meeting report of the pathogenesis of pemphigus and Pemphigoid meeting in Munich, September 2016. The Journal of Investigative Dermatology. 2017;**137**:1199-1203. DOI: 10.1016/j.

[4] Langan SM, Smeeth L, Hubbard R, Fleming KM, Smith CJP, West J. Bullous pemphigoid and pemphigus vulgaris—Incidence and mortality in the UK: Population based cohort study. BMJ. 2008;**337**:160-163. DOI: 10.1136/

[5] Hübner F, Recke A, Zillikens D, Linder R, Schmidt E. Prevalence and age distribution of pemphigus and pemphigoid diseases in Germany. The Journal of Investigative Dermatology. 2016;**136**:2495-2498. DOI: 10.1016/j.

[6] Bernard P, Vaillant L, Labeille B, Bedane C, Arbeille B, Denoeux JP, et al. Incidence and distribution of subepidermal autoimmune bullous skin diseases in three French regions. Bullous diseases French study group. Archives of

Dermatology. 1995;**131**:48-52

[7] Joly P, Baricault S, Sparsa A,

et al. Incidence and mortality of bullous pemphigoid in France. The

Bernard P, Bédane C, Duvert-Lehembre S,

[1] Kridin K, Ludwig RJ. The growing incidence of bullous

**References**

fmed.2018.00220

s40257-017-0264-2

jid.2017.01.028

bmj.a180

jid.2016.07.013

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid DOI: http://dx.doi.org/10.5772/intechopen.84933*

#### **References**

*Cellular Metabolism and Related Disorders*

**Conflict of interest**

There is no conflict of interest.

**Acronyms and abbreviations**

COL17 collagen XVII DM diabetes mellitus DPP-4 dipeptidyl peptidase-4

BP bullous pemphigoid

BPDAI bullous pemphigoid disease area index

ELISA enzyme-linked immunosorbent assays

EMA European Medicines Agency FDA Food and Drug Administration

MMP mucous membrane pemphigoid

NC16A non-collagenous 16A

BPDAI BP disease area index

genetically susceptible individuals, and they have detected that HLA-DQB1\*03:01

In conclusion, DPP-4 inhibitor-related BP tends to be presented with noninflammatory phenotype of BP, with limited extension, smaller blisters, scant perilesional erythema and eosinophilic infiltration, and normal or slightly elevated peripheral eosinophil count (**Table 1**). Anti-NC16A BP180 positivity is less common, and ELISA titers are slightly elevated, similarly to anti-BP230, but positivity for full-length BP180 or other epitopes of BP180 may be detected. Response to therapy is similar such as in classical non-DPP-4i-BP patients, regardless of withdrawal of DPP-4 inhibitors.

DPP-4i-BP dipeptidyl peptidase-4 inhibitor-associated bullous pemphigoid

allele has higher prevalence in DPP-4i-BP patients [22, 62].

**208**

**Author details**

Pécs, Pécs, Hungary

Ágnes Kinyó

provided the original work is properly cited.

\*Address all correspondence to: kinyo.agnes@pte.hu

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

Department of Dermatology, Venereology and Oncodermatology, University of

[1] Kridin K, Ludwig RJ. The growing incidence of bullous Pemphigoid: Overview and potential explanations. Frontiers in Medicine (Lausanne). 2018;**5**:220. DOI: 10.3389/ fmed.2018.00220

[2] Bernard P, Antonicelli F. Bullous pemphigoid: A review of its diagnosis, associations and treatment. American Journal of Clinical Dermatology. 2017;**18**:513-528. DOI: 10.1007/ s40257-017-0264-2

[3] Schmidt E, Spindler V, Eming R, Amagai M, Antonicelli F, Baines JF, et al. Meeting report of the pathogenesis of pemphigus and Pemphigoid meeting in Munich, September 2016. The Journal of Investigative Dermatology. 2017;**137**:1199-1203. DOI: 10.1016/j. jid.2017.01.028

[4] Langan SM, Smeeth L, Hubbard R, Fleming KM, Smith CJP, West J. Bullous pemphigoid and pemphigus vulgaris—Incidence and mortality in the UK: Population based cohort study. BMJ. 2008;**337**:160-163. DOI: 10.1136/ bmj.a180

[5] Hübner F, Recke A, Zillikens D, Linder R, Schmidt E. Prevalence and age distribution of pemphigus and pemphigoid diseases in Germany. The Journal of Investigative Dermatology. 2016;**136**:2495-2498. DOI: 10.1016/j. jid.2016.07.013

[6] Bernard P, Vaillant L, Labeille B, Bedane C, Arbeille B, Denoeux JP, et al. Incidence and distribution of subepidermal autoimmune bullous skin diseases in three French regions. Bullous diseases French study group. Archives of Dermatology. 1995;**131**:48-52

[7] Joly P, Baricault S, Sparsa A, Bernard P, Bédane C, Duvert-Lehembre S, et al. Incidence and mortality of bullous pemphigoid in France. The

Journal of Investigative Dermatology. 2012;**132**:1998-2004. DOI: 10.1038/ jid.2012.35

[8] Försti AK, Jokelainen J, Timonen M, Tasanen K. Increasing incidence of bullous pemphigoid in Northern Finland: A retrospective database study in Oulu University Hospital. The British Journal of Dermatology. 2014;**171**: 1223-1226. DOI: 10.1111/bjd.13189

[9] Stavropoulos PG, Soura E, Antoniou C. Drug-induced pemphigoid: A review of the literature. Journal of the European Academy of Dermatology and Venereology. 2014;**28**:1133-1140. DOI: 10.1111/jdv.12366

[10] Fania L, Di Zenzo G, Didona B, Pilla MA, Sobrino L, Panebianco A, et al. Increased prevalence of diabetes mellitus in bullous pemphigoid patients during the last decade. Journal of the European Academy of Dermatology and Venereology. 2018;**32**:e153-e154. DOI: 10.1111/jdv.14649

[11] Gravani A, Gaitanis G, Tsironi T, Tigas S, Bassukas ID. Changing prevalence of diabetes mellitus in bullous pemphigoid: It is the dipeptidyl peptidase-4 inhibitors. Journal of the European Academy of Dermatology and Venereology. 2018;**32**:e438-e439. DOI: 10.1111/jdv.14957

[12] Aouidad I, Fite C, Marinho E, Deschamps L, Crickx B, Descamps V. A case report of bullous pemphigoid induced by dipeptidyl peptidase-4 inhibitors. JAMA Dermatology. 2013;**149**:243-245. DOI: 10.1001/ jamadermatol.2013.1073

[13] Attaway A, Mersfelder TL, Vaishnav S, Baker JK. Bullous pemphigoid associated with dipeptidyl peptidase IV inhibitors. A case report and review of literature. Journal of Dermatological Case

Reports. 2014;**8**:24-28. DOI: 10.3315/ jdcr.2014.1166

[14] García M, Aranburu MA, Palacios-Zabalza I, Lertxundi U, Aguirre C. Dipeptidyl peptidase-IV inhibitors induced bullous pemphigoid: A case report and analysis of cases reported in the European pharmacovigilance database. Journal of Clinical Pharmacy and Therapeutics. 2016;**41**:368-370. DOI: 10.1111/jcpt.12397

[15] Harada M, Yoneda A, Haruyama S, Yabuki K, Honma Y, Hiura M, et al. Bullous Pemphigoid associated with the dipeptidyl peptidase-4 inhibitor sitagliptin in a patient with liver cirrhosis complicated with rapidly progressive hepatocellular carcinoma. Internal Medicine. 2017;**56**:2471-2474. DOI: 10.2169/internalmedicine.8703-16

[16] Maki N, Nishie W, Takazawa M, Kakurai M, Yamada T, Umemoto N, et al. Dipeptidyl peptidase-4 inhibitorassociated bullous pemphigoid in a patient with acquired reactive perforating collagenosis. The Journal of Dermatology. 2018;**45**:600-602. DOI: 10.1111/1346-8138.14254

[17] Takama H, Yoshida M, Izumi K, Yanagishita T, Muto J, Ohshima Y, et al. Dipeptidyl peptidase-4 inhibitorassociated bullous pemphigoid: Recurrence with epitope spreading. Acta Dermato-Venereologica. 2018;**98**: 983-984. DOI: 10.2340/00015555-3010

[18] Oya K, Fujii M, Taguchi S, Nishie W, Izumi K, Shimizu H. Localized bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitor treatment. European Journal of Dermatology. 2018;**28**:250-251. DOI: 10.1684/ejd.2018.3230

[19] Pasmatzi E, Monastirli A, Habeos J, Georgiou S, Tsambaos D. Dipeptidyl peptidase-4 inhibitors cause bullous pemphigoid in diabetic patients: Report of two cases. Diabetes Care. 2011;**34**:e133. DOI: 10.2337/dc11-0804

[20] Mendonça FM, Martín-Gutierrez FJ, Ríos-Martín JJ, Camacho-Martinez F. Three cases of bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors—One due to Linagliptin. Dermatology. 2016;**232**:249-253. DOI: 10.1159/000443330

[21] Haber R, Fayad AM, Stephan F, Obeid G, Tomb R. Bullous pemphigoid associated with linagliptin treatment. JAMA Dermatology. 2016;**152**:224-226. DOI: 10.1001/jamadermatol.2015.2939

[22] Kawaguchi Y, Shimauchi R, Nishibori N, Kawashima K, Oshitani S, Fujiya A, et al. Dipeptidyl peptidase-4 inhibitors-associated bullous pemphigoid: A retrospective study of 168 pemphigoid and 9,304 diabetes mellitus patients. Journal of Diabetes Investigation. 2018. DOI: 10.1111/ jdi.12877. [Epub ahead of print]

[23] Benzaquen M, Borradori L, Berbis P, Cazzaniga S, Valero R, Richard MA, et al. Dipeptidyl peptidase IV inhibitors, a risk factor for bullous pemphigoid: Retrospective multicenter case-control study from France and Switzerland. Journal of the American Academy of Dermatology. 2018;**78**:1090-1096. DOI: 10.1016/j.jaad.2017.12.038

[24] Béné J, Jacobsoone A, Coupe P, Auffret M, Babai S, Hillaire-Buys D, et al. Bullous pemphigoid induced by vildagliptin: A report of three cases. Fundamental & Clinical Pharmacology. 2015;**29**:112-114. DOI: 10.1111/bjd.14601

[25] Skandalis K, Spirova M, Gaitanis G, Tsartsarakis A, Bassukas ID. Druginduced bullous pemphigoid in diabetes mellitus patients receiving dipeptidyl peptidase-IV inhibitors plus metformin. Journal of the European Academy of Dermatology and Venereology. 2012;**26**:249-253. DOI: 10.1111/j.1468-3083.2011.04062.x

[26] Schaffer C, Buclin T, Jornayvaz FR, Cazzaniga S, Borradori L, Gilliet M,

**211**

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid*

[32] Yoshiji S, Murakami T, Harashima SI, Ko R, Kashima R, Yabe D, et al. Bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors: A report of five cases. Journal of Diabetes Investigation. 2018;**9**:445-447. DOI:

[33] Chijiwa C, Takeoka S, Kamata M, Tateishi M, Fukaya S, Hayashi K, et al. Decrease in eosinophils infiltrating into the skin of patients with dipeptidyl

[34] García-Díez I, Ivars-Lleó M, López-Aventín D, Ishii N, Hashimoto T, Iranzo P, et al. Bullous pemphigoid induced by dipeptidyl peptidase-4 inhibitors. Eight cases with clinical and immunological characterization. International Journal of Dermatology. 2018;**57**:810-816. DOI:

[35] Fania L, Salemme A, Provini A, Pagnanelli G, Collina MC, Abeni D, et al. Detection and characterization of IgG, IgE, and IgA autoantibodies in patients with bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors. Journal of the American Academy of Dermatology. 2018;**78**: 592-595. DOI: 10.1016/j.jaad.2017.09.051

[36] Horikawa H, Kurihara Y, Funakoshi T, Umegaki-Arao N, Takahashi H, Kubo A, et al. Unique clinical and serological features of bullous pemphigoid

associated with dipeptidyl peptidase-4 inhibitors. The British Journal of Dermatology. 2018;**178**:1462-1463. DOI:

peptidase-4 inhibitor-related bullous pemphigoid. The Journal of Dermatology. 2018;**45**:596-599. DOI:

10.1111/1346-8138.14245

10.1111/ijd.14005

10.1111/bjd.16479

[37] Mai Y, Nishie W, Izumi K, Yoshimoto N, Morita Y, Watanabe M, et al. Detection of anti-BP180 NC16A autoantibodies after the onset of dipeptidyl peptidase-IV inhibitorassociated bullous pemphigoid: A report of three patients. The British Journal of

10.1111/jdi.12695

*DOI: http://dx.doi.org/10.5772/intechopen.84933*

et al. Use of Dipeptidyl-peptidase IV inhibitors and bullous pemphigoid. Dermatology. 2017;**233**:401-403. DOI:

[27] Kridin K, Bergman R. Association of bullous pemphigoid with dipeptidylpeptidase 4 inhibitors in patients with diabetes: Estimating the risk of the new agents and characterizing the patients. JAMA Dermatology. 2018;**154**:1152-1158. DOI: 10.1001/

[28] Arai M, Shirakawa J, Konishi H, Sagawa N, Terauchi Y. Bullous

pemphigoid and dipeptidyl peptidase 4 inhibitors: A disproportionality analysis based on the Japanese adverse drug event report database. Diabetes Care. 2018;**41**:e130-e132. DOI: 10.2337/

[29] Béné J, Moulis G, Bennani I, Auffret M, Coupe P, Babai S, et al. French Association of Regional PharmacoVigilance Centres: Bullous pemphigoid and dipeptidyl peptidase IV inhibitors: A case-noncase study in the French Pharmacovigilance database. The British Journal of Dermatology. 2016;**175**:296-301. DOI: 10.1111/

[30] Varpuluoma O, Försti AK,

Tasanen K, et al. Oral diabetes medications other than dipeptidyl peptidase 4 inhibitors are not associated with bullous pemphigoid: A Finnish nationwide case-control study. Journal of the American Academy of Dermatology. 2018;**79**:1034-1038. DOI:

10.1016/j.jaad.2018.05.030

[31] Plaquevent M, Tétart F, Fardet L, et al. Higher frequency of dipeptidyl peptidase IV inhibitor intake in bullous pemphigoid patients than in the French general population. The Journal of Investigative Dermatology. 2018;**18**:32923-3. DOI: 10.1016/j.jid.2018

Jokelainen J, Turpeinen M, Timonen M,

10.1159/000480498

jamadermatol.2018.2352

dc18-0210

fcp.12083

*Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid DOI: http://dx.doi.org/10.5772/intechopen.84933*

et al. Use of Dipeptidyl-peptidase IV inhibitors and bullous pemphigoid. Dermatology. 2017;**233**:401-403. DOI: 10.1159/000480498

*Cellular Metabolism and Related Disorders*

Reports. 2014;**8**:24-28. DOI: 10.3315/

[20] Mendonça FM, Martín-Gutierrez FJ, Ríos-Martín JJ, Camacho-Martinez F. Three cases of bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors—One due to Linagliptin. Dermatology. 2016;**232**:249-253. DOI:

[21] Haber R, Fayad AM, Stephan F, Obeid G, Tomb R. Bullous pemphigoid associated with linagliptin treatment. JAMA Dermatology. 2016;**152**:224-226. DOI: 10.1001/jamadermatol.2015.2939

[22] Kawaguchi Y, Shimauchi R,

inhibitors-associated bullous

10.1016/j.jaad.2017.12.038

[24] Béné J, Jacobsoone A, Coupe P, Auffret M, Babai S, Hillaire-Buys D, et al. Bullous pemphigoid induced by vildagliptin: A report of three cases. Fundamental & Clinical Pharmacology. 2015;**29**:112-114. DOI: 10.1111/bjd.14601

[25] Skandalis K, Spirova M, Gaitanis G, Tsartsarakis A, Bassukas ID. Druginduced bullous pemphigoid in diabetes mellitus patients receiving dipeptidyl peptidase-IV inhibitors plus metformin. Journal of the European Academy of Dermatology and Venereology. 2012;**26**:249-253. DOI: 10.1111/j.1468-3083.2011.04062.x

[26] Schaffer C, Buclin T, Jornayvaz FR, Cazzaniga S, Borradori L, Gilliet M,

Nishibori N, Kawashima K, Oshitani S, Fujiya A, et al. Dipeptidyl peptidase-4

pemphigoid: A retrospective study of 168 pemphigoid and 9,304 diabetes mellitus patients. Journal of Diabetes Investigation. 2018. DOI: 10.1111/ jdi.12877. [Epub ahead of print]

[23] Benzaquen M, Borradori L, Berbis P, Cazzaniga S, Valero R, Richard MA, et al. Dipeptidyl peptidase IV inhibitors, a risk factor for bullous pemphigoid: Retrospective multicenter case-control study from France and Switzerland. Journal of the American Academy of Dermatology. 2018;**78**:1090-1096. DOI:

10.1159/000443330

pharmacovigilance database. Journal of Clinical Pharmacy and Therapeutics. 2016;**41**:368-370. DOI: 10.1111/jcpt.12397

[15] Harada M, Yoneda A, Haruyama S, Yabuki K, Honma Y, Hiura M, et al. Bullous Pemphigoid associated with the dipeptidyl peptidase-4 inhibitor sitagliptin in a patient with liver cirrhosis complicated with rapidly progressive hepatocellular carcinoma. Internal Medicine. 2017;**56**:2471-2474. DOI: 10.2169/internalmedicine.8703-16

[16] Maki N, Nishie W, Takazawa M, Kakurai M, Yamada T, Umemoto N, et al. Dipeptidyl peptidase-4 inhibitorassociated bullous pemphigoid in a patient with acquired reactive

perforating collagenosis. The Journal of Dermatology. 2018;**45**:600-602. DOI:

[17] Takama H, Yoshida M, Izumi K, Yanagishita T, Muto J, Ohshima Y, et al. Dipeptidyl peptidase-4 inhibitorassociated bullous pemphigoid:

Dermato-Venereologica. 2018;**98**: 983-984. DOI: 10.2340/00015555-3010

DOI: 10.1684/ejd.2018.3230

Recurrence with epitope spreading. Acta

[18] Oya K, Fujii M, Taguchi S, Nishie W, Izumi K, Shimizu H. Localized bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitor treatment. European Journal of Dermatology. 2018;**28**:250-251.

[19] Pasmatzi E, Monastirli A, Habeos J, Georgiou S, Tsambaos D. Dipeptidyl peptidase-4 inhibitors cause bullous pemphigoid in diabetic patients: Report of two cases. Diabetes Care. 2011;**34**:e133. DOI: 10.2337/dc11-0804

10.1111/1346-8138.14254

[14] García M, Aranburu MA, Palacios-Zabalza I, Lertxundi U, Aguirre C. Dipeptidyl peptidase-IV inhibitors induced bullous pemphigoid:

A case report and analysis of cases reported in the European

jdcr.2014.1166

**210**

[27] Kridin K, Bergman R. Association of bullous pemphigoid with dipeptidylpeptidase 4 inhibitors in patients with diabetes: Estimating the risk of the new agents and characterizing the patients. JAMA Dermatology. 2018;**154**:1152-1158. DOI: 10.1001/ jamadermatol.2018.2352

[28] Arai M, Shirakawa J, Konishi H, Sagawa N, Terauchi Y. Bullous pemphigoid and dipeptidyl peptidase 4 inhibitors: A disproportionality analysis based on the Japanese adverse drug event report database. Diabetes Care. 2018;**41**:e130-e132. DOI: 10.2337/ dc18-0210

[29] Béné J, Moulis G, Bennani I, Auffret M, Coupe P, Babai S, et al. French Association of Regional PharmacoVigilance Centres: Bullous pemphigoid and dipeptidyl peptidase IV inhibitors: A case-noncase study in the French Pharmacovigilance database. The British Journal of Dermatology. 2016;**175**:296-301. DOI: 10.1111/ fcp.12083

[30] Varpuluoma O, Försti AK, Jokelainen J, Turpeinen M, Timonen M, Tasanen K, et al. Oral diabetes medications other than dipeptidyl peptidase 4 inhibitors are not associated with bullous pemphigoid: A Finnish nationwide case-control study. Journal of the American Academy of Dermatology. 2018;**79**:1034-1038. DOI: 10.1016/j.jaad.2018.05.030

[31] Plaquevent M, Tétart F, Fardet L, et al. Higher frequency of dipeptidyl peptidase IV inhibitor intake in bullous pemphigoid patients than in the French general population. The Journal of Investigative Dermatology. 2018;**18**:32923-3. DOI: 10.1016/j.jid.2018 [32] Yoshiji S, Murakami T, Harashima SI, Ko R, Kashima R, Yabe D, et al. Bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors: A report of five cases. Journal of Diabetes Investigation. 2018;**9**:445-447. DOI: 10.1111/jdi.12695

[33] Chijiwa C, Takeoka S, Kamata M, Tateishi M, Fukaya S, Hayashi K, et al. Decrease in eosinophils infiltrating into the skin of patients with dipeptidyl peptidase-4 inhibitor-related bullous pemphigoid. The Journal of Dermatology. 2018;**45**:596-599. DOI: 10.1111/1346-8138.14245

[34] García-Díez I, Ivars-Lleó M, López-Aventín D, Ishii N, Hashimoto T, Iranzo P, et al. Bullous pemphigoid induced by dipeptidyl peptidase-4 inhibitors. Eight cases with clinical and immunological characterization. International Journal of Dermatology. 2018;**57**:810-816. DOI: 10.1111/ijd.14005

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[36] Horikawa H, Kurihara Y, Funakoshi T, Umegaki-Arao N, Takahashi H, Kubo A, et al. Unique clinical and serological features of bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors. The British Journal of Dermatology. 2018;**178**:1462-1463. DOI: 10.1111/bjd.16479

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[54] Röhrborn D, Wronkowitz N, Eckel J. DPP4 in Diabetes. Frontiers in Immunology. 2015;**6**:386. DOI: 10.3389/ fimmu.2015.00386

[55] Gonzalez-Gronow M, Kaczowka S, Gawdi G, Pizzo SV. Dipeptidyl peptidase IV (DPP IV/CD26) is a cellsurface plasminogen receptor. Frontiers in Bioscience. 2008;**13**:1610-1618

[56] Thielitz A, Ansorge S, Bank U, Tager M, Wrenger S, Gollnick H, et al. The ectopeptidases dipeptidyl peptidase IV (DP IV) and aminopeptidase N (APN) and their related enzymes as possible targets in the treatment of skin diseases. Frontiers in Bioscience. 2008;**13**:2364-2375

[57] Schmidt E, Wehr B, Tabengwa EM, Reimer S, Bröcker EB, Zillikens D. Elevated expression and release of tissue-type, but not urokinasetype, plasminogen activator after binding of autoantibodies to bullous pemphigoid antigen 180 in cultured human keratinocytes. Clinical

and Experimental Immunology. 2004;**135**:497-504

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[61] Filippatos TD, Athyros VG, Elisaf MS. The pharmacokinetic considerations and adverse effects of DPP-4 inhibitors [corrected]. Expert Opinion on Drug Metabolism & Toxicology. 2014;**10**:787-812. DOI: 10.1517/17425255.2014.907274

[62] Ujiie H, Muramatsu K, Mushiroda T, Ozeki T, Miyoshi H, Iwata H, et al. HLA-DQB1\*03:01 as a biomarker for genetic susceptibility to bullous pemphigoid induced by DPP-4 inhibitors. The Journal of Investigative Dermatology. 2018;**138**:1201-1204. DOI: 10.1016/j. jid.2017.11.023

### *Edited by Jesmine Khan and Po-Shiuan Hsieh*

This book deals with a vital topic: metabolism in the cells of the body and various disorders due to its imbalance and/or diseases that disrupt the metabolism of the body. The objective of this book was to collect and compile up-to-date information from reputed researchers in their respective fields to disseminate the latest information about topics that have profound effects on the metabolic processes in the body including insulin resistance, diabetes mellitus, hypothyroidism, metabolic syndrome, glycogen storage disease, and the urea cycle disorder. In total, there are 12 chapters in this book in which the authors have shared their research findings and real-life experiences in managing their patients.

Published in London, UK © 2020 IntechOpen © CIPhotos / iStock

Cellular Metabolism and Related Disorders

Cellular Metabolism

and Related Disorders

*Edited by Jesmine Khan and Po-Shiuan Hsieh*