**1. State of the art**

Celiac disease (CD) is an immune-mediated disorder triggered by gluten ingestion in genetically susceptible subjects. About 1% of the European and North American population are affected, but the number of CD cases currently undiagnosed is suspected to be far superior to known cases due to the prevalence of forms with nonspecific symptoms. An increasing incidence of CD has been observed in developing countries, possibly due to westernization of the local diet, changes in wheat production/preparation, and increasing simplicity of diagnostic techniques. The principal determinant of genetic susceptibility to CD is the major histocompatibility class II HLA molecules. The HLA-DQ2 haplotype is expressed in the majority of patients with CD, whereas the HLA-DQ8 haplotype is expressed only in a minority of patients. However, although the presence of the DQ2 and DQ8 haplotypes is a necessary condition, it is not sufficient for the development of CD. In point of fact, only 10% of people with a genetic predisposition goes on to develop CD.

Gluten is a protein complex rich in proline and glutamine and is found in wheat, rye, and barley. The term gluten refers to a group of prolamins of wheat (gliadin and glutenin). Other prolamins are found in rye (secalin) and barley (hordein) and are genetically similar to each other.

It is particularly interesting that maize, while containing prolamins, causes no mucosal damage in celiac patients, most likely because a different phylogenetic evolution of maize prolamins makes its consumption safe for celiac subjects and not toxic.

Gluten is poorly digested in the human intestine regardless of the presence of celiac disease. Its oligopeptides cross the intestinal mucosa and reach the submucosa where they are deamidated by transglutaminase type 2 (tTG2). Deamidation promotes high affinity binding with HLA DQ2 and DQ8 expressed on the surface of T lymphocytes. In celiac patients, this process triggers an inflammatory and immune-mediated response, typical of the disease. T lymphocytes recognize the HLA complex and release various cytokines including IL-15 and IFN-γ. These molecules induce the activation and clonal expansion of B cells which produce antibodies against gluten as well as autoantibodies against tTG2. Other cytokines stimulate fibroblasts and inflammatory cells to secrete matrix metalloproteinases with consequent tissue remodeling and further release of tTG2 in the extracellular compartment. At the same time, there is an increase in intraepithelial lymphocytes with cytolytic activity which determines epithelial damage.

The typical histological lesions of celiac disease are villous atrophy, intraepithelial lymphocytosis, and crypt hyperplasia. Villous atrophy consists of decreased villous height and alteration of normal crypt/villous ratio (3:1) until total disappearance of villi. Intraepithelial lymphocytosis is defined as a number of intraepithelial lymphocyte (IEL) greater than 30 per 100 enterocytes. Crypt hyperplasia is the extension of the regenerative epithelial crypts associated with changes in the presence of more than one mitosis per crypt.

These elementary lesions associated with celiac disease are identified through duodenal biopsies from endoscopic evaluation. Multiple biopsies of the duodenum (at least one biopsy of the bulb and four of the distal part of the duodenum) are required to make a diagnosis as elementary lesions are not exclusive and frequently may be patchy [1].

In children, adding biopsies of the bulb increases diagnostic reliability, owing to the fact that in 10% of pediatric patients, villous atrophy is exclusively located in the duodenal bulb [2].

Histological changes can be classified according to the Marsh classification which identifies three entities: (1) type 1 or infiltrative lesions (normal villous and crypt architecture, normal villous/crypt ratio, and an increased number of intraepithelial lymphocytes); (2) type 2 or hyperplastic lesion (normal villous architecture, hyperplasia of the glandular element with an increased number of mitoses, and increased intraepithelial lymphocytes); and (3) type 3 or destructive lesion (varying degrees of villous atrophy associated with hyperplasia of the glandular crypt and increased intraepithelial lymphocytes). Oberhuber et al. [3] proposed a different classification dividing the Marsh type 3 lesion into three subgroups according to the severity of villous atrophy: (3a) mild villous atrophy and pathological increase of IELs; (3b) moderate villous atrophy and pathological increase of IELs; and (3c) total villous atrophy and pathological increase of IELs.

Diagnosis of CD is based not only on histology but also on the presence of specific serological markers which should be performed in patients on a glutencontaining diet.

Anti-tTG2 is circulating, gluten-dependent, autoantibodies that target transglutaminase 2, the principal self-antigen involved in pathogenesis of CD. IgA anti-tTG2 has high sensitivity (97%) and specificity (91%) and is deemed the single most

**55**

*The Emerging Role of the Autophagy Process in Children with Celiac Disease: Current Status…*

reliable test for detection of CD in primary care in cases of clinical suspicion or as a screening test in relatives of celiac patients or in people with an increased risk of developing CD. In comparison with the anti-endomysial antibody, the anti-tTG2 IgA assay has greater sensitivity and reproducibility. It is important to remember that IgA deficiency is more common among celiac patients than in the general population; therefore, in cases of low serum IgA levels, IgG class anti-tTG2 should be evaluated. Anti-endomysial antibodies (EMA) are directed against the intermyofibril substance of smooth muscle, which may correspond to either a reticulin-like structure or a surface component of smooth muscle fibrils. These are detected by indirect immunofluorescence on monkey esophagus cells and on human umbilical cord cells as a substrate. The EMA assay specificity is high (100%), but it is also IgAbased and the EMA IgG assay is not widely available. Anti-endomysial antibodies are considered a confirmatory assay and should be used only in cases of borderline

Testing for antibodies directed against native gliadin is no longer recommended. However, antibodies against synthetic deamidated IgG class gliadin peptides (anti-

Histological evaluation and serological markers are important for diagnosis but also for testing efficacy of alternative therapies for celiac disease, as mentioned below. Currently, the only effective treatment for celiac disease is a strict gluten-free diet (GFD). The aim of dietary regimen is recovery of intestinal damage (usually within 24 months), disappearance of serological markers, and resolution of symptoms, when present. Moreover, a GFD improves nutritional parameters including

Celiac patients should avoid all products containing wheat, barley, and rye for life. Complete elimination of gluten is very difficult, especially due to contamina-

Strict avoidance of gluten is demanding especially in Mediterranean countries

The definition "gluten-free" is reserved for foods having less than 20 parts per million of gluten. The lowest quantity of gluten known to be responsible for mucosal damage ranges from 10 to 50 mg per day. A gluten intake of less than 10 mg per

Nevertheless, some patients may be more sensitive than others are to gluten

The gluten-free diet has numerous difficulties; a significant lifestyle change is required by patients, and it may be challenging especially in Western countries

Furthermore, gluten-free products are more expensive [4] and are known to

Hypothetical gluten exposure in restaurants may also be a source of anxiety for

It is extremely important that patients know potential hidden sources of gluten and obtain precise information about gluten-free substitute and their fiber and nutrient content. Celiac patients should have high-fiber diets and frequently need supplementation of iron, folic acid, vitamin B12, and vitamin D. It may be very

Serological markers are used to assess adhesion to gluten-free diet and its efficacy. First of all, in a patient with persistent symptoms, despite a gluten-free diet, it is mandatory to verify strictly compliance to GFD and in particular to investigate

exposure. Therefore, compliance to GFD should be strict and lifelong.

useful to refer patients to a dietitian at the time of diagnosis.

where gluten ingestion in normal diet is high as well as in adolescence and in asymptomatic children diagnosed by screening. Therefore, CD subjects should be monitored annually for adherence to the GFD. Verification of the disappearance of

*DOI: http://dx.doi.org/10.5772/intechopen.80692*

positive or possibly false positive results for anti-tTG2.

DPG) have a diagnostic role in cases of IgA deficiency.

the specific antibodies is important during follow-up.

body mass index and bone mineral density.

tion of other foods with traces of gluten.

day is unlikely to cause mucosal damage.

where gluten is contained in a lot of foods.

have poor palatability and high fat content.

celiac patients [5].

### *The Emerging Role of the Autophagy Process in Children with Celiac Disease: Current Status… DOI: http://dx.doi.org/10.5772/intechopen.80692*

reliable test for detection of CD in primary care in cases of clinical suspicion or as a screening test in relatives of celiac patients or in people with an increased risk of developing CD. In comparison with the anti-endomysial antibody, the anti-tTG2 IgA assay has greater sensitivity and reproducibility. It is important to remember that IgA deficiency is more common among celiac patients than in the general population; therefore, in cases of low serum IgA levels, IgG class anti-tTG2 should be evaluated.

Anti-endomysial antibodies (EMA) are directed against the intermyofibril substance of smooth muscle, which may correspond to either a reticulin-like structure or a surface component of smooth muscle fibrils. These are detected by indirect immunofluorescence on monkey esophagus cells and on human umbilical cord cells as a substrate. The EMA assay specificity is high (100%), but it is also IgAbased and the EMA IgG assay is not widely available. Anti-endomysial antibodies are considered a confirmatory assay and should be used only in cases of borderline positive or possibly false positive results for anti-tTG2.

Testing for antibodies directed against native gliadin is no longer recommended. However, antibodies against synthetic deamidated IgG class gliadin peptides (anti-DPG) have a diagnostic role in cases of IgA deficiency.

Histological evaluation and serological markers are important for diagnosis but also for testing efficacy of alternative therapies for celiac disease, as mentioned below.

Currently, the only effective treatment for celiac disease is a strict gluten-free diet (GFD). The aim of dietary regimen is recovery of intestinal damage (usually within 24 months), disappearance of serological markers, and resolution of symptoms, when present. Moreover, a GFD improves nutritional parameters including body mass index and bone mineral density.

Celiac patients should avoid all products containing wheat, barley, and rye for life. Complete elimination of gluten is very difficult, especially due to contamination of other foods with traces of gluten.

Strict avoidance of gluten is demanding especially in Mediterranean countries where gluten ingestion in normal diet is high as well as in adolescence and in asymptomatic children diagnosed by screening. Therefore, CD subjects should be monitored annually for adherence to the GFD. Verification of the disappearance of the specific antibodies is important during follow-up.

The definition "gluten-free" is reserved for foods having less than 20 parts per million of gluten. The lowest quantity of gluten known to be responsible for mucosal damage ranges from 10 to 50 mg per day. A gluten intake of less than 10 mg per day is unlikely to cause mucosal damage.

Nevertheless, some patients may be more sensitive than others are to gluten exposure. Therefore, compliance to GFD should be strict and lifelong.

The gluten-free diet has numerous difficulties; a significant lifestyle change is required by patients, and it may be challenging especially in Western countries where gluten is contained in a lot of foods.

Furthermore, gluten-free products are more expensive [4] and are known to have poor palatability and high fat content.

Hypothetical gluten exposure in restaurants may also be a source of anxiety for celiac patients [5].

It is extremely important that patients know potential hidden sources of gluten and obtain precise information about gluten-free substitute and their fiber and nutrient content. Celiac patients should have high-fiber diets and frequently need supplementation of iron, folic acid, vitamin B12, and vitamin D. It may be very useful to refer patients to a dietitian at the time of diagnosis.

Serological markers are used to assess adhesion to gluten-free diet and its efficacy. First of all, in a patient with persistent symptoms, despite a gluten-free diet, it is mandatory to verify strictly compliance to GFD and in particular to investigate

*Celiac Disease - From the Bench to the Clinic*

genetically similar to each other.

Gluten is a protein complex rich in proline and glutamine and is found in wheat, rye, and barley. The term gluten refers to a group of prolamins of wheat (gliadin and glutenin). Other prolamins are found in rye (secalin) and barley (hordein) and are

It is particularly interesting that maize, while containing prolamins, causes no mucosal damage in celiac patients, most likely because a different phylogenetic evolution of maize prolamins makes its consumption safe for celiac subjects and not toxic. Gluten is poorly digested in the human intestine regardless of the presence of celiac disease. Its oligopeptides cross the intestinal mucosa and reach the submucosa where they are deamidated by transglutaminase type 2 (tTG2). Deamidation promotes high affinity binding with HLA DQ2 and DQ8 expressed on the surface of T lymphocytes. In celiac patients, this process triggers an inflammatory and immune-mediated response, typical of the disease. T lymphocytes recognize the HLA complex and release various cytokines including IL-15 and IFN-γ. These molecules induce the activation and clonal expansion of B cells which produce antibodies against gluten as well as autoantibodies against tTG2. Other cytokines stimulate fibroblasts and inflammatory cells to secrete matrix metalloproteinases with consequent tissue remodeling and further release of tTG2 in the extracellular compartment. At the same time, there is an increase in intraepithelial lymphocytes

The typical histological lesions of celiac disease are villous atrophy, intraepithelial lymphocytosis, and crypt hyperplasia. Villous atrophy consists of decreased villous height and alteration of normal crypt/villous ratio (3:1) until total disappearance of villi. Intraepithelial lymphocytosis is defined as a number of intraepithelial lymphocyte (IEL) greater than 30 per 100 enterocytes. Crypt hyperplasia is the extension of the regenerative epithelial crypts associated with changes in the

These elementary lesions associated with celiac disease are identified through duodenal biopsies from endoscopic evaluation. Multiple biopsies of the duodenum (at least one biopsy of the bulb and four of the distal part of the duodenum) are required to make a diagnosis as elementary lesions are not exclusive and frequently

In children, adding biopsies of the bulb increases diagnostic reliability, owing to the fact that in 10% of pediatric patients, villous atrophy is exclusively located in the

Histological changes can be classified according to the Marsh classification which identifies three entities: (1) type 1 or infiltrative lesions (normal villous and crypt architecture, normal villous/crypt ratio, and an increased number of intraepithelial lymphocytes); (2) type 2 or hyperplastic lesion (normal villous architecture, hyperplasia of the glandular element with an increased number of mitoses, and increased intraepithelial lymphocytes); and (3) type 3 or destructive lesion (varying degrees of villous atrophy associated with hyperplasia of the glandular crypt and increased intraepithelial lymphocytes). Oberhuber et al. [3] proposed a different classification dividing the Marsh type 3 lesion into three subgroups according to the severity of villous atrophy: (3a) mild villous atrophy and pathological increase of IELs; (3b) moderate villous atrophy and pathological increase of IELs; and (3c)

Diagnosis of CD is based not only on histology but also on the presence of specific serological markers which should be performed in patients on a gluten-

Anti-tTG2 is circulating, gluten-dependent, autoantibodies that target transglutaminase 2, the principal self-antigen involved in pathogenesis of CD. IgA anti-tTG2 has high sensitivity (97%) and specificity (91%) and is deemed the single most

with cytolytic activity which determines epithelial damage.

presence of more than one mitosis per crypt.

total villous atrophy and pathological increase of IELs.

may be patchy [1].

duodenal bulb [2].

containing diet.

**54**

the possibility of inadvertent gluten exposure. Second, it is important to exclude other causes of persistent symptoms. It is necessary to underline the hypothetic presence of alternative diagnosis (i.e., lactose or fructose intolerance, irritable bowel syndrome, microscopic colitis, pancreatic insufficiency, and small intestinal bacterial overgrowth). Another reason for the recurrence of clinical manifestations is refractory celiac disease, whereby CD patients present symptoms of malabsorption and villous atrophy despite a GFD for more than 12 months. In the primary form, there is no initial response to a diet, while in the secondary one, a relapse occurs after an initial response to a GFD. Patients with refractory CD are at risk of developing enteropathy-associated T cell lymphomas.
