**4. Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis**

#### **4.1. History and nosology**

case definition will be determined by RegiSCAR study, which comprises data collected from 6 European countries and the JSCAR Japanese registry. The incidence following phenytoin

DIHS has a relapsing remitting course lasting several weeks to months despite the withdrawal of the offending drug and this has been postulated to result from the sequential reactivation of herpes viruses analogous to that observed in graft versus host disease. The precise role of HHV-6 in DIHS is unclear. One theory is that HHV-6 triggers DIHS through its reactivation within T cells resulting in HHV-6 stimulated T cells cross-reacting with the culprit drug, following which there is sequential activation of heterologous herpes viruses. The alternative explanation is that drug specific T cells are activated resulting in reactivation of the viral

The histological features of DIHS are relatively non-specific and typically comprise a superfi‐ cial perivascular lymphocytic infiltrate. As the understanding of the disease mechanisms emerge, novel findings such as granulomatous inflammation have also been identified.

The diagnostic criteria consist of the typical clinical features and laboratory abnormalities. Confirmation of the role of the causative agent by skin testing is contraindicated because of the risk of a generalized reaction. The utility of LTTs is unclear as they are often negative early in the course of disease possibly as a result of regulatory T cell activation. LTTs may become positive after 5-7 weeks as the expanded regulatory T cell population are removed by apoptosis

A prolonged course of oral corticosteroids is required to treat DIHS given the relapsing

AGEP is rare with an incidence of 1-5 cases per million per year. The clinical manifestations are characterised by fever and the rapid appearance of disseminated sterile pustules 3-5 days after the commencement of treatment. It is accompanied by a marked neutrophilia. Mucous membranes are not typically involved. The drugs conferring the highest risk of AGEP according to the EuroSCAR study are aminopenicillins, pristinamycin, hydroxychloroquine, antibacterial sulphonamides, terbinafine and diltiazem. The pathogenesis of AGEP involves the initial influx of CD8 cytotoxic T cells resulting in apoptosis of keratinocytes and formation of vesicles. Then CXCL-8 producing CD4 cells enter the epidermis resulting in neutrophil mediated inflammation and formation of pustules. As a result the histology reveals intraepi‐ dermal usually subcorneal pustules and an accompanying neutrophilic and lymphocytic infiltrate. Epicutaneous patch testing may also support the diagnosis by causing a localized pustular reaction 48-96 hours after the offending drug is applied. The condition usually resolves by 15 days after the causative drug is withdrawn but oral corticosteroid therapy may be necessary in some individuals. The mortality rate is up to 5% and mostly occurs in the

remitting nature of the condition. The mortality rate is estimated to be 10-20%.

therapy is estimated to be 1 in 1000 to 10000 exposures.

48 Skin Biopsy - Diagnosis and Treatment

genome and sequential reactivation of herpes viruses.

at the end of the immune response.

elderly who have significant comorbidities.

**3. AGEP**

SJS and TEN were once considered as variants of erythema multiforme (EM), a condition first described by Ferdinand von Hebra in 1860 [1] as a mild and relapsing eruption of target lesions affecting the acral regions. Mucosal involvement occurs in up to 70% of cases of EM. In 1922, two American paediatricians, Albert Stevens and Frank Johnson, described two cases of fever, stomatitis, purulent conjunctivitis, and a generalized eruption of purple papules in boys aged 7 and 8 years, respectively [2]. Both cases were distinguished from EM by the prolonged high fever, and the generalized distribution and heavy terminal crusting of the skin lesions. Bernard Thomas proposed two categories of EM in 1950: erythema multiforme minor, as described by von Hebra, and erythema multiforme major, a severe form that encompassed SJS [3]. Alan Lyell, a Scottish dermatologist, termed the condition toxic epidermal necrolysis (TEN) after reporting four cases of an acute life threatening mucocutaneous disorder characterized by diffuse erythema followed by extensive epidermal detachment manifesting as blistering and sloughing of the skin [4]. Although SJS and TEN were initially considered distinct entities, it was later proposed that they form a continuum along the same disease process and differ mainly in the extent of involvement [5],[6]. It was also proposed that EM major and SJS are distinct conditions, with EM major characterised by acral target-like lesion typical of EM minor but with mucosal involvement. SJS was applied to cases of mucous membrane involvement and a more extensive eruption of atypical targetoid lesions, blisters or sloughing of the skin [7]. The distinction between EM and SJS are consistent with observations regarding differences in etiology, demography and histopathology and not just confined to variations in the severity of disease. Most cases of EM are related to infection especially those with recurrent disease, which is related to herpes simplex virus (HSV) infection [8]-[10] in contrast to SJS which usually is an idiosyncratic reaction to drugs [11]. EM typically affects young adults in their 20s and 30s although approximately 20% of cases involve children [12],[13] whereas SJS/TEN occurs at any age [11]. Histopathology in EM in contrast to SJS/TEN consists of a denser infiltrate of lymphocytes and less apoptosis of keratinocytes [14].

In 1993, a classification scheme was proposed that is widely but not universally adopted that arbitrarily defines SJS and TEN according to the extent of epidermal detachment [7]. In SJS, epidermal loss affects less than 10% of the total body surface area (TBSA) whereas TEN involves greater than 30% of the TBSA. Epidermal detachment between 10 and 30% of the TBSA is classified as SJS/TEN overlap.

## **4.2. Epidemiology**

The epidemiology of SJS/TEN and other severe cutaneous adverse reactions (SCARs) has been more accurately determined in recent years due to registries that have been established mainly across Europe comprising cases that are reviewed by expert committees and based on predefined and validated criteria. A population-based registry was commenced in Germany in 1990 to collect all hospitalised cases of SJS, TEN and EM major [15]. An international casecontrol study was conducted between 1989 and 1995 in France, Germany, Italy and Portugal (SCAR study) focusing on cases of SJS/TEN requiring hospitalisation [16],[17]. A European case-control surveillance study of SCARs (EuroSCAR study) was conducted between 1997 and 2001 in Austria, France, Germany, Israel, Italy, and the Netherlands investigating both SJS/TEN [11] and AGEP [18] that resulted in admission to hospital. In 2003, the European registry on SCARs (RegiSCAR) was commenced collecting biological samples across the same countries that participated in the EuroSCAR study. This network, which is focused on SJS/TEN and AGEP, has spawned numerous studies on epidemiology, pharmacogenetics and histopa‐ thology and includes community cases that requiring hospitalisation as well as cases that developed during hospital admissions. These registries not only provide valuable information on the epidemiology of SCAR but they have enabled close scrutiny of the availability and prescription of high-risk drugs. For example, the SCAR study resulted in the withdrawal of chlormezanone from the market and restricted indications for cotrimoxazole and phenobar‐ bitol [17].

observations [17],[19]. The most likely explanation is that valproic acid was frequently

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 51

A pooled analysis of the SCAR and EuroSCAR data was performed for children under 15 years of age and showed that anti-bacterial sulphonamides, phenobarbitol, lamotrigine and carba‐

Infection with *Mycoplasma pneumoniae* is a known cause of SJS especially in the paediatric population and a few cases of TEN have been reported to complicate infection with this agent [13],[21]. However, the EuroSCAR study, failed to show that infection is a risk factor on its own although there is a suggestion that it may modestly increase the risk of SJS/TEN from medication. SJS/TEN has been reported in association with vaccinations [22] and exposure to

SJS/TEN is characterized, as per the original descriptions, by fever, blistering skin eruption and severe mucositis [2],[4]. The skin lesions initially appear as atypical target –like or targetoid lesions, which are erythematous macules that contain a central purpuric blister (Fig. 1). Lesions

**Figure 1.** Atypical target-like or targetoid lesions in a patient with SJS characterized by an erythematous macule with

mazepine were strongly associated with SJS/TEN in this paediatric population [20].

coadministered with high-risk drugs.

industrial chemicals and fumigants [23].

**4.4. Clinical presentation**

a central blister.

*4.3.2. Other causes*

The incidence of SJS/TEN is 1-2 cases/million inhabitants/year [15]. The EuroSCAR study published in 2008 comprised 379 cases that included 134 cases of SJS, 136 cases of SJS/TEN overlap, and 109 cases TEN spanning a geographical area encompassing over a 100 million inhabitants. The median age of cases was found to be 50 years (range 1-95 years), and a female preponderance (62% of cases) was noted [11].

#### **4.3. Etiology**

#### *4.3.1. Drugs*

Drugs are nearly always the cause of SJS/TEN. Over 220 medications have been implicated but only relatively a few are responsible for the majority of cases. The EuroSCAR study comprised 379 cases of SJS/TEN and 1505 age-matched controls, who were patients admitted to hospital for other acute illnesses [11]. Univariate relative risk (uRR) and multivariate relative risk (mRR) were calculated for each drug suspected of causing SJS/TEN. The drugs found to confer the highest risk were cotrimoxazole (uRR 102), other anti-bacterial sulphonamides (uRR 53), carbamazepine (mRR 72), nevirapine (uRR >22), allopurinol (mRR 18), phenytoin (mRR 17), oxicam-NSAIDs (mRR 16), lamotrigine (uRR >14), and sertraline (mRR 11). Drugs that were found to have a significant but lower risk included acetic acid-NSAIDs, macrolides, quino‐ lones, cephalosporins, tetracyclines and aminopenicillins. SJS/TEN typically occurs with drugs that are taken on a long-term basis. The median latency between the onset of medication use and the occurrence of SJS/TEN in the EuroSCAR study was found to be less than 4 weeks (range 1-8 weeks): carbamazepine 15 days, phenobarbitol 17 days, allopurinol 20 days, phenytoin 24 days. Pantoprazole and tramadol were associated with high uRRs, 18 and 20, respectively, but the frequent co-medication with highly suspected drugs and the timing of the onset of SJS/TEN were not suggestive of a true risk. Commonly used medications not associated with a risk of SJS/TEN included beta-blockers, ACE-inhibitors, calcium channel blockers, thiazide diuretics, furosemide, propionic acid-NSAIDs, sulphonylureas, and insulin. Interestingly, valproic acid was not shown to have a significant risk, which is in contrast to previous observations [17],[19]. The most likely explanation is that valproic acid was frequently coadministered with high-risk drugs.

A pooled analysis of the SCAR and EuroSCAR data was performed for children under 15 years of age and showed that anti-bacterial sulphonamides, phenobarbitol, lamotrigine and carba‐ mazepine were strongly associated with SJS/TEN in this paediatric population [20].

#### *4.3.2. Other causes*

(SCAR study) focusing on cases of SJS/TEN requiring hospitalisation [16],[17]. A European case-control surveillance study of SCARs (EuroSCAR study) was conducted between 1997 and 2001 in Austria, France, Germany, Israel, Italy, and the Netherlands investigating both SJS/TEN [11] and AGEP [18] that resulted in admission to hospital. In 2003, the European registry on SCARs (RegiSCAR) was commenced collecting biological samples across the same countries that participated in the EuroSCAR study. This network, which is focused on SJS/TEN and AGEP, has spawned numerous studies on epidemiology, pharmacogenetics and histopa‐ thology and includes community cases that requiring hospitalisation as well as cases that developed during hospital admissions. These registries not only provide valuable information on the epidemiology of SCAR but they have enabled close scrutiny of the availability and prescription of high-risk drugs. For example, the SCAR study resulted in the withdrawal of chlormezanone from the market and restricted indications for cotrimoxazole and phenobar‐

The incidence of SJS/TEN is 1-2 cases/million inhabitants/year [15]. The EuroSCAR study published in 2008 comprised 379 cases that included 134 cases of SJS, 136 cases of SJS/TEN overlap, and 109 cases TEN spanning a geographical area encompassing over a 100 million inhabitants. The median age of cases was found to be 50 years (range 1-95 years), and a female

Drugs are nearly always the cause of SJS/TEN. Over 220 medications have been implicated but only relatively a few are responsible for the majority of cases. The EuroSCAR study comprised 379 cases of SJS/TEN and 1505 age-matched controls, who were patients admitted to hospital for other acute illnesses [11]. Univariate relative risk (uRR) and multivariate relative risk (mRR) were calculated for each drug suspected of causing SJS/TEN. The drugs found to confer the highest risk were cotrimoxazole (uRR 102), other anti-bacterial sulphonamides (uRR 53), carbamazepine (mRR 72), nevirapine (uRR >22), allopurinol (mRR 18), phenytoin (mRR 17), oxicam-NSAIDs (mRR 16), lamotrigine (uRR >14), and sertraline (mRR 11). Drugs that were found to have a significant but lower risk included acetic acid-NSAIDs, macrolides, quino‐ lones, cephalosporins, tetracyclines and aminopenicillins. SJS/TEN typically occurs with drugs that are taken on a long-term basis. The median latency between the onset of medication use and the occurrence of SJS/TEN in the EuroSCAR study was found to be less than 4 weeks (range 1-8 weeks): carbamazepine 15 days, phenobarbitol 17 days, allopurinol 20 days, phenytoin 24 days. Pantoprazole and tramadol were associated with high uRRs, 18 and 20, respectively, but the frequent co-medication with highly suspected drugs and the timing of the onset of SJS/TEN were not suggestive of a true risk. Commonly used medications not associated with a risk of SJS/TEN included beta-blockers, ACE-inhibitors, calcium channel blockers, thiazide diuretics, furosemide, propionic acid-NSAIDs, sulphonylureas, and insulin. Interestingly, valproic acid was not shown to have a significant risk, which is in contrast to previous

bitol [17].

50 Skin Biopsy - Diagnosis and Treatment

**4.3. Etiology**

*4.3.1. Drugs*

preponderance (62% of cases) was noted [11].

Infection with *Mycoplasma pneumoniae* is a known cause of SJS especially in the paediatric population and a few cases of TEN have been reported to complicate infection with this agent [13],[21]. However, the EuroSCAR study, failed to show that infection is a risk factor on its own although there is a suggestion that it may modestly increase the risk of SJS/TEN from medication. SJS/TEN has been reported in association with vaccinations [22] and exposure to industrial chemicals and fumigants [23].

#### **4.4. Clinical presentation**

SJS/TEN is characterized, as per the original descriptions, by fever, blistering skin eruption and severe mucositis [2],[4]. The skin lesions initially appear as atypical target –like or targetoid lesions, which are erythematous macules that contain a central purpuric blister (Fig. 1). Lesions

**Figure 1.** Atypical target-like or targetoid lesions in a patient with SJS characterized by an erythematous macule with a central blister.

are symmetrically distributed often starting on the face and thorax before spreading to other areas (Fig. 2). The scalp is typically spared. Blisters result from epidermal detachment and they are easily breached resulting in dark red oozing erosions. Lesions exhibit Nikolsky's sign, which is epidermal separation induced by gentle lateral pressure applied to the skin surface. The skin then sloughs rapidly over several days as a result of separation of large sheets of the epidermis from the dermis. Fulminant cases of TEN have been reported were total loss of the epidermis occurs within 24 hours [24]. New lesions may continue to erupt for up to 4 weeks. However, the growth of a new epithelium occurs after several days and individual lesions are completely re-epithelialized after a mean of 3 weeks. Cicatrization of the mucous membranes may take longer to complete.

At least two mucosal surfaces are involved in 90% of cases of SJS/TEN [25]. Oropharyngeal involvement causes severe pain and odynophagia as a result of erosion and crusting (Fig. 3). Ocular regions may show a purulent conjunctivitis, pseudomembrane formation and corneal ulceration as a result of sloughing of conjunctival and corneal epithelia (Fig. 4). Urethritis may result in dysuria and even urinary retention. Sloughing of the tracheal and bronchial epithe‐ lium occurs in up to 30% of cases and may result in hypoxia, bronchial hypersecretion, pulmonary edema and bronchiolitis obliterans and the need for mechanical ventilation [26], [27]. The gastrointestinal tract can also be involved resulting in per rectal bleeding [28].

(a)

(b)

and thorax before spreading to other areas.

**Figure 2.** Symmetrical distribution of targetoid lesions in a patient with SJS, which typically first appear on the face

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 53

The mortality of SJS is generally below 10% whereas 30-50% of TEN patients die in the acute phase of the illness mostly as a result of skin failure. Infection and sepsis with multiorgan failure is the most common of death. The causative organisms are usually *Staphylococcus aureus* and *Pseudomonas aeruginosa* [29]. Fluid and electrolyte imbalances occur as a result of increased transepidermal water loss and impaired intake of nutrition due to odynophagia from stomatitis. Less common fatal complications include adult respiratory distress syndrome, pulmonary embolism and gastrointestinal haemorrhage [30],[31]. Mortality is accurately predicted by the SCORTEN scale (Table 1) and should be computed within 24 hours and 3 days following admission [32]-[34].

Chronic complications occur frequently following the acute phase of SJS/TEN. The most serious sequelae relate to the eye. The chronic ocular consequences are that of a cicatrization of the conjunctiva and symblepharon formation, severe dry eye, trichiasis, eyelid margin keratinization, and limbal stem cell deficiency, all of which combine to cause corneal ulceration and scarring and loss of vision (Fig. 5) [35],[36]. Patients may also experience chronic photo‐ phobia and eye pain [37]. Skin sequelae include scarring, pigmentation abnormalities, and shedding of hair and nails [38]. Vulvovaginal involvement can result in stenosis [39]. Vulvar adenosis can occur in young women several years after resolution of the acute episode and can present with tender, erosive, haemorrhagic lesions [40]. Phimosis can occur in men [41]. Bronchopulmonary complications confer a poor prognosis and include chronic bronchitis, bronchiolitis obliterans, bronchiolitis obliterans with organizing pneumonia, bronchiectasis [42],[43] Oesophageal stricture and webbing has also been described and can result in dysphagia [44].

are symmetrically distributed often starting on the face and thorax before spreading to other areas (Fig. 2). The scalp is typically spared. Blisters result from epidermal detachment and they are easily breached resulting in dark red oozing erosions. Lesions exhibit Nikolsky's sign, which is epidermal separation induced by gentle lateral pressure applied to the skin surface. The skin then sloughs rapidly over several days as a result of separation of large sheets of the epidermis from the dermis. Fulminant cases of TEN have been reported were total loss of the epidermis occurs within 24 hours [24]. New lesions may continue to erupt for up to 4 weeks. However, the growth of a new epithelium occurs after several days and individual lesions are completely re-epithelialized after a mean of 3 weeks. Cicatrization of the mucous membranes

At least two mucosal surfaces are involved in 90% of cases of SJS/TEN [25]. Oropharyngeal involvement causes severe pain and odynophagia as a result of erosion and crusting (Fig. 3). Ocular regions may show a purulent conjunctivitis, pseudomembrane formation and corneal ulceration as a result of sloughing of conjunctival and corneal epithelia (Fig. 4). Urethritis may result in dysuria and even urinary retention. Sloughing of the tracheal and bronchial epithe‐ lium occurs in up to 30% of cases and may result in hypoxia, bronchial hypersecretion, pulmonary edema and bronchiolitis obliterans and the need for mechanical ventilation [26], [27]. The gastrointestinal tract can also be involved resulting in per rectal bleeding [28].

The mortality of SJS is generally below 10% whereas 30-50% of TEN patients die in the acute phase of the illness mostly as a result of skin failure. Infection and sepsis with multiorgan failure is the most common of death. The causative organisms are usually *Staphylococcus aureus* and *Pseudomonas aeruginosa* [29]. Fluid and electrolyte imbalances occur as a result of increased transepidermal water loss and impaired intake of nutrition due to odynophagia from stomatitis. Less common fatal complications include adult respiratory distress syndrome, pulmonary embolism and gastrointestinal haemorrhage [30],[31]. Mortality is accurately predicted by the SCORTEN scale (Table 1) and should be computed within 24 hours and 3

Chronic complications occur frequently following the acute phase of SJS/TEN. The most serious sequelae relate to the eye. The chronic ocular consequences are that of a cicatrization of the conjunctiva and symblepharon formation, severe dry eye, trichiasis, eyelid margin keratinization, and limbal stem cell deficiency, all of which combine to cause corneal ulceration and scarring and loss of vision (Fig. 5) [35],[36]. Patients may also experience chronic photo‐ phobia and eye pain [37]. Skin sequelae include scarring, pigmentation abnormalities, and shedding of hair and nails [38]. Vulvovaginal involvement can result in stenosis [39]. Vulvar adenosis can occur in young women several years after resolution of the acute episode and can present with tender, erosive, haemorrhagic lesions [40]. Phimosis can occur in men [41]. Bronchopulmonary complications confer a poor prognosis and include chronic bronchitis, bronchiolitis obliterans, bronchiolitis obliterans with organizing pneumonia, bronchiectasis [42],[43] Oesophageal stricture and webbing has also been described and can result in

may take longer to complete.

52 Skin Biopsy - Diagnosis and Treatment

days following admission [32]-[34].

dysphagia [44].

**Figure 2.** Symmetrical distribution of targetoid lesions in a patient with SJS, which typically first appear on the face and thorax before spreading to other areas.

**Severe Cutaneous Adverse Reactions Severe Cutaneous**

Age >40 years 1 Presence of malignancy 1 Heart rate >120/min 1 TBSA involved >10% 1 Serum urea > 10 mmol/L (28 mg/dL) 1 Serum glucose >14 mmol/L (252 mg/dL) 1 Serum bicarbonate <20 mmol/L (20 mEq/L) 1

SCORTEN Mortality (%) 0-1 3.2 2 12.1 3 35.3 4 58.3 ≥5 90

SJS/TEN results from the T- and NK-cell mediated extensive apoptosis of keratinocytes. The pharmaco-immune (p-i) concept, the mechanism by which the drug binds directly with the T cell receptor (TCR) causing activation of proapoptotic pathways. Granulysin is the major mediator of apoptosis in SJS/TEN. Apoptosis is also mediated through involved Fas-FasL

It is generally accepted that in SJS/TEN, the parent drug binds directly and non-covalently to the MHC and the TCR of primed effector and memory T cells [45]. Naïve T cells are not sufficiently stimulated by a p-i drug and additional signals are required [46]. T cells may be primed by infection or autoimmune disease resulting in high cytokine levels such as IL-2 and IFN-γ resulting in increased expression of MHC and costimulatory molecules. This may provide an explanation for the increased incidence of drug hypersensitivity in inflammatory and infectious diseases. The drug may also bind to toll-like receptors resulting in the expression of costimulatory molecules by dendritic cells. For drugs such as cotrimoxazole, lamotrigine, and carbamazepine, the p-i concept may not be the sole mechanism involved; metabolites may

**Table 1.** SCORTEN

**4.5. Pathogenesis**

interaction, and the release of granzyme and perforin.

*4.5.1. The pharmaco-immune (p-i) concept*

also play a role through haptenization [47].

**Adverse Reactions**

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 55

**Figure 3.** Oral mucositis in a patient with SJS depicted as sloughing, necrosis and crusting of the inner labial surfaces.

**Figure 4.** Purulent conjunctivitis in a patient with SJS accompanied by pseudomembrane formation, which results from sloughing of conjunctival and corneal surfaces.


**Table 1.** SCORTEN

**Figure 3.** Oral mucositis in a patient with SJS depicted as sloughing, necrosis and crusting of the inner labial surfaces.

**Figure 4.** Purulent conjunctivitis in a patient with SJS accompanied by pseudomembrane formation, which results

from sloughing of conjunctival and corneal surfaces.

54 Skin Biopsy - Diagnosis and Treatment

#### **4.5. Pathogenesis**

SJS/TEN results from the T- and NK-cell mediated extensive apoptosis of keratinocytes. The pharmaco-immune (p-i) concept, the mechanism by which the drug binds directly with the T cell receptor (TCR) causing activation of proapoptotic pathways. Granulysin is the major mediator of apoptosis in SJS/TEN. Apoptosis is also mediated through involved Fas-FasL interaction, and the release of granzyme and perforin.

#### *4.5.1. The pharmaco-immune (p-i) concept*

It is generally accepted that in SJS/TEN, the parent drug binds directly and non-covalently to the MHC and the TCR of primed effector and memory T cells [45]. Naïve T cells are not sufficiently stimulated by a p-i drug and additional signals are required [46]. T cells may be primed by infection or autoimmune disease resulting in high cytokine levels such as IL-2 and IFN-γ resulting in increased expression of MHC and costimulatory molecules. This may provide an explanation for the increased incidence of drug hypersensitivity in inflammatory and infectious diseases. The drug may also bind to toll-like receptors resulting in the expression of costimulatory molecules by dendritic cells. For drugs such as cotrimoxazole, lamotrigine, and carbamazepine, the p-i concept may not be the sole mechanism involved; metabolites may also play a role through haptenization [47].

of the caspase cascade and apoptosis. The source of the FasL is unclear. Viard et al showed that the FasL was is present on the surface of keratinocytes and in the serum of patients with TEN but not on the surface of keratinocytes or in the serum of patients with maculopapular exanthems and normal controls [51]. A further study demonstrated that FasL was not consti‐ tutively expressed on the surface of keratinocytes but are transported to the cell membrane after damage to the keratinocyte [52]. Abe et al, however, found that the source of FasL was

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 57

Nassif et al showed that mononuclear cells from blister fluid induce cytotoxicity via perforin and granzyme B [54]. This cytotoxicity was blocked by inhibiting perforin/granzyme but not by inhibiting Fas. Perforin and granzyme are proteins stored in the granules of CTLs. Upon recognition of a target cell, the CTL releases perforin, which create 16-nm channels in the target cell membrane. Granzyme B, a protease passes through these channels to activate the caspase cascade. The loss of T regulatory cell function in the acute stage of SJS/TEN may further

Posadas et al, showed that both Fas-FasL and perforin/granzyme pathways may be involved in SJS/TEN. They found a direct correlation between disease severity and levels of perforin and granzyme B in patients with maculopapular exanthems, SJS and TEN. FasL was detected in the PBMCs and blister fluid of patients in SJS and TEN but not in those in maculopapular

Nassif et al, also showed a potential role for cytokines in the pathogenesis of SJS/TEN. He found elevated levels of IFN-γ, soluble TNF, IL-10, soluble FasL in the blister fluid of TEN patients. Although they disputed the central role of FasL, they hypothesised that drug specific CTLs secrete IFN-γ, which activates keratinocytes to produce TNF, a cytokine that upregulated MHC class I molecules. This increases exposure of keratinocytes to CTL resulting in perforin/ granzyme-mediated apoptosis. IL-10 serves to downregulate the inflammatory reaction [57].

More recently, TRAIL (TNF related apoptosis inducing ligand) and TWEAK (TNF-like weak inducer of apoptosis) were shown to be present in blister fluid from TEN patients [36]. They are released by CD1a and CD14 cells and initiate apoptosis of keratinocytes in a MHC-class I-

It was observed in the 1990s that the most commonly offending drugs varied among different ethnic populations. In Western countries, the most commonly implicated agents of SJS/TEN were NSAIDs and sulphonamides [17]. In contrast, carbamazepine was found to be the leading cause of SJS/TEN in Southeast Asian countries, including India, Malaysia, Singapore, Taiwan and Hong Kong [58]. Interestingly, carbamazepine in Western countries causes more cases of DIHS than SJS/TEN. Allopurinol is also a frequent case of SJS/TEN and DIHS but does not

contribute to the epidermal damage caused by effector T cells [55].

exanthema, suggesting that Fas-FasL is involved in more severe reactions [56].

PBMCs and not keratinocytes [53].

independent manner.

**4.6. Risk factors for SJS/TEN**

appear to have a racial bias [59].

*4.6.1. Genetic susceptibility*

**Figure 5.** Cicatrization of the bulbar and palpebral conjunctival surfaces with resultant symblepharon formation, shortening of the fornix, and distichiasis.

#### *4.5.2. Granulysin*

A recent study by Chung et al using global gene expression profiling showed that granulysin RNA was the most significant cytotoxic molecule expressed in blister cells from patients with SJS/TEN. Granulysin protein concentrations were 2-4 times higher than perforin, granzyme B, and FasL and depleting granulysin reduced cytotoxicity [48]. Granulysin is a cationic cytolytic protein produced by CTL, NK and NKT cells [49]. The 15-kDa-precursor form, found in blister fluid, induced skin necrosis when injected into mice and exhibited significant cytotoxicity in vitro. This contrasted with the minimal cytotoxicity induced by perforin, granzyme B, and FasL [48]. Granulysin is also a proinflammatory molecule that causes an increase in the expression of chemokines (RANTES/CCL5, MCP-1, MCP-3, MIP-1α/CCL3) and cytokines (IL-1, IL-6, IFN-α) resulting in the recruitment of T cells, monocytes and other inflammatory cells [50].

#### *4.5.3. Fas-FasL, perforin/ granzyme and TNF pathways*

Viard et al, showed that the binding of FasL to Fas expressed on the surface of keratinocytes resulted in their apoptosis [51]. The cytoplasmic death domain of Fas undergoes conforma‐ tional changes and trimerization upon recognition of FasL. This results in the recruitment of the Fas-associated death domain (FADD), which binds to procaspase 8 resulting in triggering of the caspase cascade and apoptosis. The source of the FasL is unclear. Viard et al showed that the FasL was is present on the surface of keratinocytes and in the serum of patients with TEN but not on the surface of keratinocytes or in the serum of patients with maculopapular exanthems and normal controls [51]. A further study demonstrated that FasL was not consti‐ tutively expressed on the surface of keratinocytes but are transported to the cell membrane after damage to the keratinocyte [52]. Abe et al, however, found that the source of FasL was PBMCs and not keratinocytes [53].

Nassif et al showed that mononuclear cells from blister fluid induce cytotoxicity via perforin and granzyme B [54]. This cytotoxicity was blocked by inhibiting perforin/granzyme but not by inhibiting Fas. Perforin and granzyme are proteins stored in the granules of CTLs. Upon recognition of a target cell, the CTL releases perforin, which create 16-nm channels in the target cell membrane. Granzyme B, a protease passes through these channels to activate the caspase cascade. The loss of T regulatory cell function in the acute stage of SJS/TEN may further contribute to the epidermal damage caused by effector T cells [55].

Posadas et al, showed that both Fas-FasL and perforin/granzyme pathways may be involved in SJS/TEN. They found a direct correlation between disease severity and levels of perforin and granzyme B in patients with maculopapular exanthems, SJS and TEN. FasL was detected in the PBMCs and blister fluid of patients in SJS and TEN but not in those in maculopapular exanthema, suggesting that Fas-FasL is involved in more severe reactions [56].

Nassif et al, also showed a potential role for cytokines in the pathogenesis of SJS/TEN. He found elevated levels of IFN-γ, soluble TNF, IL-10, soluble FasL in the blister fluid of TEN patients. Although they disputed the central role of FasL, they hypothesised that drug specific CTLs secrete IFN-γ, which activates keratinocytes to produce TNF, a cytokine that upregulated MHC class I molecules. This increases exposure of keratinocytes to CTL resulting in perforin/ granzyme-mediated apoptosis. IL-10 serves to downregulate the inflammatory reaction [57].

More recently, TRAIL (TNF related apoptosis inducing ligand) and TWEAK (TNF-like weak inducer of apoptosis) were shown to be present in blister fluid from TEN patients [36]. They are released by CD1a and CD14 cells and initiate apoptosis of keratinocytes in a MHC-class Iindependent manner.

## **4.6. Risk factors for SJS/TEN**

#### *4.6.1. Genetic susceptibility*

*4.5.2. Granulysin*

shortening of the fornix, and distichiasis.

56 Skin Biopsy - Diagnosis and Treatment

cells [50].

*4.5.3. Fas-FasL, perforin/ granzyme and TNF pathways*

A recent study by Chung et al using global gene expression profiling showed that granulysin RNA was the most significant cytotoxic molecule expressed in blister cells from patients with SJS/TEN. Granulysin protein concentrations were 2-4 times higher than perforin, granzyme B, and FasL and depleting granulysin reduced cytotoxicity [48]. Granulysin is a cationic cytolytic protein produced by CTL, NK and NKT cells [49]. The 15-kDa-precursor form, found in blister fluid, induced skin necrosis when injected into mice and exhibited significant cytotoxicity in vitro. This contrasted with the minimal cytotoxicity induced by perforin, granzyme B, and FasL [48]. Granulysin is also a proinflammatory molecule that causes an increase in the expression of chemokines (RANTES/CCL5, MCP-1, MCP-3, MIP-1α/CCL3) and cytokines (IL-1, IL-6, IFN-α) resulting in the recruitment of T cells, monocytes and other inflammatory

**Figure 5.** Cicatrization of the bulbar and palpebral conjunctival surfaces with resultant symblepharon formation,

Viard et al, showed that the binding of FasL to Fas expressed on the surface of keratinocytes resulted in their apoptosis [51]. The cytoplasmic death domain of Fas undergoes conforma‐ tional changes and trimerization upon recognition of FasL. This results in the recruitment of the Fas-associated death domain (FADD), which binds to procaspase 8 resulting in triggering

It was observed in the 1990s that the most commonly offending drugs varied among different ethnic populations. In Western countries, the most commonly implicated agents of SJS/TEN were NSAIDs and sulphonamides [17]. In contrast, carbamazepine was found to be the leading cause of SJS/TEN in Southeast Asian countries, including India, Malaysia, Singapore, Taiwan and Hong Kong [58]. Interestingly, carbamazepine in Western countries causes more cases of DIHS than SJS/TEN. Allopurinol is also a frequent case of SJS/TEN and DIHS but does not appear to have a racial bias [59].

The most striking genetic association was detected in a cohort of Han Chinese in Taiwan, where the *HLA-B\*1502* allele was found in 100% of the 44 patients with carbamazepineinduced SJS/TEN and only 3% of the carbamazepine-tolerant individuals; OR 2504 [126– 49522] [60]. These findings were replicated in an extended cohort of subjects of Chinese descent originating from separated geographic areas of China, Taiwan, and the United States [61]. This association with carbamazepine-induced SJS/TEN, however, was not found in individuals with European [62] and Japanese ancestries [63], respectively, and therefore the allele appears relevant in the context of ethnicity. In a recent study compris‐ ing 12 patients of Northern European ancestry with carbamazepine-induced SJS/TEN, 5 (42%) carried the *HLA-A\*3101* allele, as compared with 10 (4%) of the 257 control sub‐ jects; OR 25.93 [4.93-116.18] [64]. The results of this study are yet to be replicated in other cohorts of subjects with Northern European ancestry. In a Japanese study, The *HLA-A\*3101* allele was found in 5/6 (83.3%) carbamazepine-induced SJS/TEN compared to 47/376 (12.5%) carbamazepine-tolerant patients; OR 33.9 [3.9-295.6]. Larger patient sample sizes are required to confirm this association in the Japanese where the allele frequency is 9% [65]. Interestingly the *HLA-A\*3101* allele was shown to be associated with maculopap‐ ular exanthem (OR 17.5 [4.6-66.5]) but not SJS/TEN in a Han Chinese population [66].

not in a European population. It is also plausible is that SJS/TEN is a polygenic disorder, with many susceptibility and protective alleles in genes involved in the pathogenesis of the disease. Polymorphisms in the proapoptotic gene *Fas-L* [71], the toll-like receptor 3 gene [72], and in the IL-4 receptor/IL-13 signalling pathway [73] have all been recently described in a Japanese

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 59

The FDA and Health Canada have issued warnings for carbamazepine stating that persons with ancestry in genetically at-risk populations should be screened for the presence of *HLA-B\*1502* prior to initiating treatment [74]. Genetic screening for *HLA-B\*1502* in a high risk population such as the Han Chinese has a 100% sensitivity and 97% specificity and its presence confers a 7.7% positive predictive value for carbamazepine-induced SJS/TEN whereas its absence has a 100% negative predictive value [58]. The odds ratio in test-positive Chinese patients to test-negative patients of having carbamazepine-induced SJS/TEN is >3200. Al‐ though 3% of patients who are test-positive may never develop the disease, the serious and life-threatening consequences of developing SJS/TEN and the availability of alternative drugs, justifies its exclusion from these individuals. The lack of prevalence of *HLA-B\*1502* in non-Asian populations may limit its cost effectiveness as a screening tool in these populations and cannot be currently recommended. A recent study demonstrated the benefit of genetic screening; in a Taiwanese population, screening for the *HLA-B\*1502* allele resulted in no cases of SJS/TEN in 4501 patients who were negative for the allele [75]. The authors concluded that this would have prevented 10 cases of SJS/TEN. Despite the FDA recommendations, screening is not routinely performed partly because of the lack of availability of cost effective and rapid methods of detection [76]. Susceptibility alleles can be identified by high resolution sequence based HLA typing after a 20 ml sample of blood is collected in an ADC tube. However, this highly specialized and relatively expensive diagnostic technique is limited to a small number of laboratories that focus on transplantation medicine and may be limited by longer turnaround times of up to 3-4 weeks. Many laboratories have now developed high resolution genetic testing using a sequence-specific primer assay method for the detection of this allele from samples collected in either 7-10 ml of whole blood (EDTA tube) or buccal swabs (provided by the testing laboratory). The assay can be performed within 3-4 hours. Such a strategy is not novel and has been very successful in virtually abolishing the incidence of *HLA-B\*5701* associated abacavir hypersensitivity in HIV-infected patients [77]. Multiplexed PCRs can be

It is important to note that the *HLA-B\*1502* allele does not predispose to carbamazepineinduced DIHS, maculopapular eruptions or other adverse reactions and continued vigilance

Currently, there is no recommendation for genetic screening prior to the commencement of allopurinol therapy. Although such a strategy is plausible, studies are required to determine

The EuroSCAR study showed that HIV infection conferred the highest risk of SJS/TEN; multivariate relative risk (mvRR) 12 [2.4-59]. Other disease associations included collagen

for the symptoms of SCAR needs to be maintained if treatment is commenced [61].

the benefits of screening for the *HLA\*5801* allele in at risk populations.

study. Such alleles may also vary in different populations.

utilized to assess multiple alleles.

*4.6.2. Diseases*

A study comprising a Han Chinese cohort in Taiwan demonstrated the presence of the *HLA-B\*5801* allele in all 51 patients with allopurinol-induced SCAR (21 with TEN, 30 with DIHS) compared with only 15% (20/135) in allopurinol-tolerant subjects; OR 580.3 [34.4-9780.9] [67].

The role of these HLA alleles in the pathogenesis of SCAR is unclear. Certain HLA alleles may bind to particular drugs more robustly than other alleles. Furthermore, the binding of the drug in SJS/TEN is MHC class I restricted, which is consistent with the prominent role of CD8 cells in the pathogenesis of the disease. If an allele has a functional effect that may play a role in the pathogenesis of disease, this association will be consistently observed across different popu‐ lations. The differences observed between the Chinese and European studies may be partly explained by the fact that pharmacogenetic studies are likely to yield positive results when conducted in a population with a high frequency of such an allele [69]. The risk of disease from a genetic polymorphism is influenced by its prevalence. The *HLA-B\*1502* allele frequency is 4.8 to 12.8% in Southeast Asians compared to 0-0.1% observed in Northern Europeans [58]. For instance, *HLA-B\*1502* is of low prevalence in Caucasians and hence, if it is a true suscept‐ ibility allele, a very large sample size is required in this population to detect a significant odds ratio of sufficient power. In contrast, the allele frequency of *HLA-A\*3101* is 2-5% in Northern Europeans [70] and the sample size required to demonstrate an association in a sufficiently powered study is less than that for the *HLA-B\*1502* allele. The *HLA-B\*5801* allele, in contrast to *HLA-B\*1502* is more evenly distributed among different racial groups [59] and hence, associations, albeit weaker, have been demonstrated in other ethnic groups such as the Southern Japanese [63] and in whites (OR 80 [34-157]) [68].

Another explanation is that *HLA-B\*1502*, is a marker of a true disease contributing allele through strong linkage disequilibrium, which varies between populations. In other words, the same high-risk allele may have a different pattern of association with marker alleles and therefore *HLA-B\*1502* is in strong linkage disequilibrium in the Han Chinese population, but not in a European population. It is also plausible is that SJS/TEN is a polygenic disorder, with many susceptibility and protective alleles in genes involved in the pathogenesis of the disease. Polymorphisms in the proapoptotic gene *Fas-L* [71], the toll-like receptor 3 gene [72], and in the IL-4 receptor/IL-13 signalling pathway [73] have all been recently described in a Japanese study. Such alleles may also vary in different populations.

The FDA and Health Canada have issued warnings for carbamazepine stating that persons with ancestry in genetically at-risk populations should be screened for the presence of *HLA-B\*1502* prior to initiating treatment [74]. Genetic screening for *HLA-B\*1502* in a high risk population such as the Han Chinese has a 100% sensitivity and 97% specificity and its presence confers a 7.7% positive predictive value for carbamazepine-induced SJS/TEN whereas its absence has a 100% negative predictive value [58]. The odds ratio in test-positive Chinese patients to test-negative patients of having carbamazepine-induced SJS/TEN is >3200. Al‐ though 3% of patients who are test-positive may never develop the disease, the serious and life-threatening consequences of developing SJS/TEN and the availability of alternative drugs, justifies its exclusion from these individuals. The lack of prevalence of *HLA-B\*1502* in non-Asian populations may limit its cost effectiveness as a screening tool in these populations and cannot be currently recommended. A recent study demonstrated the benefit of genetic screening; in a Taiwanese population, screening for the *HLA-B\*1502* allele resulted in no cases of SJS/TEN in 4501 patients who were negative for the allele [75]. The authors concluded that this would have prevented 10 cases of SJS/TEN. Despite the FDA recommendations, screening is not routinely performed partly because of the lack of availability of cost effective and rapid methods of detection [76]. Susceptibility alleles can be identified by high resolution sequence based HLA typing after a 20 ml sample of blood is collected in an ADC tube. However, this highly specialized and relatively expensive diagnostic technique is limited to a small number of laboratories that focus on transplantation medicine and may be limited by longer turnaround times of up to 3-4 weeks. Many laboratories have now developed high resolution genetic testing using a sequence-specific primer assay method for the detection of this allele from samples collected in either 7-10 ml of whole blood (EDTA tube) or buccal swabs (provided by the testing laboratory). The assay can be performed within 3-4 hours. Such a strategy is not novel and has been very successful in virtually abolishing the incidence of *HLA-B\*5701* associated abacavir hypersensitivity in HIV-infected patients [77]. Multiplexed PCRs can be utilized to assess multiple alleles.

It is important to note that the *HLA-B\*1502* allele does not predispose to carbamazepineinduced DIHS, maculopapular eruptions or other adverse reactions and continued vigilance for the symptoms of SCAR needs to be maintained if treatment is commenced [61].

Currently, there is no recommendation for genetic screening prior to the commencement of allopurinol therapy. Although such a strategy is plausible, studies are required to determine the benefits of screening for the *HLA\*5801* allele in at risk populations.

#### *4.6.2. Diseases*

The most striking genetic association was detected in a cohort of Han Chinese in Taiwan, where the *HLA-B\*1502* allele was found in 100% of the 44 patients with carbamazepineinduced SJS/TEN and only 3% of the carbamazepine-tolerant individuals; OR 2504 [126– 49522] [60]. These findings were replicated in an extended cohort of subjects of Chinese descent originating from separated geographic areas of China, Taiwan, and the United States [61]. This association with carbamazepine-induced SJS/TEN, however, was not found in individuals with European [62] and Japanese ancestries [63], respectively, and therefore the allele appears relevant in the context of ethnicity. In a recent study compris‐ ing 12 patients of Northern European ancestry with carbamazepine-induced SJS/TEN, 5 (42%) carried the *HLA-A\*3101* allele, as compared with 10 (4%) of the 257 control sub‐ jects; OR 25.93 [4.93-116.18] [64]. The results of this study are yet to be replicated in other cohorts of subjects with Northern European ancestry. In a Japanese study, The *HLA-A\*3101* allele was found in 5/6 (83.3%) carbamazepine-induced SJS/TEN compared to 47/376 (12.5%) carbamazepine-tolerant patients; OR 33.9 [3.9-295.6]. Larger patient sample sizes are required to confirm this association in the Japanese where the allele frequency is 9% [65]. Interestingly the *HLA-A\*3101* allele was shown to be associated with maculopap‐ ular exanthem (OR 17.5 [4.6-66.5]) but not SJS/TEN in a Han Chinese population [66].

58 Skin Biopsy - Diagnosis and Treatment

A study comprising a Han Chinese cohort in Taiwan demonstrated the presence of the *HLA-B\*5801* allele in all 51 patients with allopurinol-induced SCAR (21 with TEN, 30 with DIHS) compared with only 15% (20/135) in allopurinol-tolerant subjects; OR 580.3 [34.4-9780.9] [67].

The role of these HLA alleles in the pathogenesis of SCAR is unclear. Certain HLA alleles may bind to particular drugs more robustly than other alleles. Furthermore, the binding of the drug in SJS/TEN is MHC class I restricted, which is consistent with the prominent role of CD8 cells in the pathogenesis of the disease. If an allele has a functional effect that may play a role in the pathogenesis of disease, this association will be consistently observed across different popu‐ lations. The differences observed between the Chinese and European studies may be partly explained by the fact that pharmacogenetic studies are likely to yield positive results when conducted in a population with a high frequency of such an allele [69]. The risk of disease from a genetic polymorphism is influenced by its prevalence. The *HLA-B\*1502* allele frequency is 4.8 to 12.8% in Southeast Asians compared to 0-0.1% observed in Northern Europeans [58]. For instance, *HLA-B\*1502* is of low prevalence in Caucasians and hence, if it is a true suscept‐ ibility allele, a very large sample size is required in this population to detect a significant odds ratio of sufficient power. In contrast, the allele frequency of *HLA-A\*3101* is 2-5% in Northern Europeans [70] and the sample size required to demonstrate an association in a sufficiently powered study is less than that for the *HLA-B\*1502* allele. The *HLA-B\*5801* allele, in contrast to *HLA-B\*1502* is more evenly distributed among different racial groups [59] and hence, associations, albeit weaker, have been demonstrated in other ethnic groups such as the

Another explanation is that *HLA-B\*1502*, is a marker of a true disease contributing allele through strong linkage disequilibrium, which varies between populations. In other words, the same high-risk allele may have a different pattern of association with marker alleles and therefore *HLA-B\*1502* is in strong linkage disequilibrium in the Han Chinese population, but

Southern Japanese [63] and in whites (OR 80 [34-157]) [68].

The EuroSCAR study showed that HIV infection conferred the highest risk of SJS/TEN; multivariate relative risk (mvRR) 12 [2.4-59]. Other disease associations included collagen vascular disease mvRR 2.2 [0.9-5.0], recent malignancy mvRR 2.7 [1.3-5.7], recent radiotherapy mvRR 2.1 [0.5-9.0], or acute infection in the past 4 weeks [1.2-2.3] [11].

bullae [93]. The mononuclear predominantly T cell dermal infiltrate is generally sparse but dense infiltrates can also be present. Quinn et al, has shown an extensive infiltrate was associated with a 71% mortality rate, a moderate infiltrate with a 53% mortality, and a sparse infiltrate with a 27% mortality, respectively [94]. A fresh sample for direct immunofluoresence (DIF) reveals an absence of immunoglobulin and complement deposition. The cornified layer remains intact. Immunohistochemistry usually reveals a predominance of CD8 cells in the epidermis and CD4 cells in the dermis. A fresh sample for direct immunofluoresence (DIF)

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 61

**Figure 6.** Low power view of a skin biopsy from a patient with SJS demonstrates separation of the epidermis from the dermis at the level of the stratum spinosum and basal cell layer resulting in the formation of subepidermal bullae

Cultures on blood, wounds and mucosal lesions should be performed to evaluate for super‐

A recent pilot study showed that serum granulysin levels may be raised early in the course of disease but rapidly wanes with progression of disease [95]. Further studies are required to determine whether this assay will prove to be a useful early diagnostic test for SJS/TEN.

Skin tests and oral challenges are contraindicated in SJS/TEN because of the risk of inducing a recurrence of disease. Patch testing has not been investigated extensively. The biggest cohort comprised 22 patients and showed a poor sensitivity of only 9% [96]. Lymphocyte transfor‐ mation tests (LTTs) assesses the proliferation of the patient's peripheral blood T cells cultured

infection. Serology may be performed for *Mycoplasma pneumoniae* if indicated.

(Hematoxylin-eosin, original magnification x40).

**4.8. Allergy testing**

reveals an absence of immunoglobulin and complement deposition.

#### *4.6.3. Pharmacokinetics*

The EuroSCAR study revealed an increased risk of SJS/TEN at higher doses of allopurinol; adjusted odds ratio (OR) 36 [17-76] for doses ≥200 mg daily compared with an adjusted OR 3.0 [1.1-8.4] for doses <200 mg daily [78]. This study also revealed that the risk was mostly confined to short-term use (≤8 weeks, unadjusted OR 261 [36-∞]). Allopurinol should be commenced at a dose of 100 mg daily and increased by 100 mg increments until the desired serum uric acid level is attained. Previous reports have shown that allopurinol is commenced at inappropriate doses [79] and that higher doses are associated with an increased incidence of acute events [80]. It is likely that the rapid accumulation of the chemically reactive metabolite oxypurinol when higher doses of allopurinol are commenced increases the risk of SJS/TEN [81],[82]. This drug accumulation hypothesis is further supported by the 4.7 fold increased incidence of allopuri‐ nol-induced SCAR in renal insufficiency [83]. The established indications for allopurinol are treatment of hyperuricemia associated with chronic gout, acute uric acid nephropathy, recurrent uric acid stone formation, enzyme disorders of purine metabolism, and in the management of tumour lysis. Allopurinol is not indicated in the majority of patients with asymptomatic hyperuricemia [84]. However, allopurinol is inappropriately prescribed in up to 86% of cases [85]-[87]. A comparison of allopurinol exposure between the SCAR (1989-1993) and EuroSCAR (1997-2001) studies showed a 2-3 fold increase in exposure for both patients and control subjects, which may be attributed to the increased prescribing of the drug for the treatment of asymptomatic hyperuricemia. The authors of the EuroSCAR study postulate that up to 48 of the 56 cases of allopurinol-induced SJS/TEN could have been prevented if the treatment guidelines for prescribing allopurinol were followed.

Lamotrigine when commenced at high doses can also overwhelm the detoxifying capacity resulting in an increased risk of SJS/TEN and DIHS [88]. The incidence has reduced signifi‐ cantly as a result of the now conventional practice of gradually titrating the dose [89]. Coad‐ ministration of certain drugs can predispose to SCAR by competition for the same enzymebinding site. Reactions to lamotrigine are more common when given in combination with valproic acid as the addition of valproic acid inhibits the clearance of lamotrigine by competing for glucoronic acid conjugation [90].

The role of slow acetylation phenotypes of N-acetyltransferase was thought to confer suscept‐ ibility of sulphonamide-induced SJS/TEN in two small studies [91],[92] but this needs confir‐ mation in larger studies.

#### **4.7. Diagnosis**

A presumptive diagnosis of SJS/TEN is made clinically and is confirmed with a skin biopsy (Figs. 6 & 7). Early lesions demonstrate vacuolar alteration and scattered necrotic keratinocytes in the epidermal layers at the level of the stratum spinosum and the basal cell layer. Later, full thickness epidermal necrosis is evident, which eventuates in the formation of subepidermal bullae [93]. The mononuclear predominantly T cell dermal infiltrate is generally sparse but dense infiltrates can also be present. Quinn et al, has shown an extensive infiltrate was associated with a 71% mortality rate, a moderate infiltrate with a 53% mortality, and a sparse infiltrate with a 27% mortality, respectively [94]. A fresh sample for direct immunofluoresence (DIF) reveals an absence of immunoglobulin and complement deposition. The cornified layer remains intact. Immunohistochemistry usually reveals a predominance of CD8 cells in the epidermis and CD4 cells in the dermis. A fresh sample for direct immunofluoresence (DIF) reveals an absence of immunoglobulin and complement deposition.

**Figure 6.** Low power view of a skin biopsy from a patient with SJS demonstrates separation of the epidermis from the dermis at the level of the stratum spinosum and basal cell layer resulting in the formation of subepidermal bullae (Hematoxylin-eosin, original magnification x40).

Cultures on blood, wounds and mucosal lesions should be performed to evaluate for super‐ infection. Serology may be performed for *Mycoplasma pneumoniae* if indicated.

A recent pilot study showed that serum granulysin levels may be raised early in the course of disease but rapidly wanes with progression of disease [95]. Further studies are required to determine whether this assay will prove to be a useful early diagnostic test for SJS/TEN.

#### **4.8. Allergy testing**

vascular disease mvRR 2.2 [0.9-5.0], recent malignancy mvRR 2.7 [1.3-5.7], recent radiotherapy

The EuroSCAR study revealed an increased risk of SJS/TEN at higher doses of allopurinol; adjusted odds ratio (OR) 36 [17-76] for doses ≥200 mg daily compared with an adjusted OR 3.0 [1.1-8.4] for doses <200 mg daily [78]. This study also revealed that the risk was mostly confined to short-term use (≤8 weeks, unadjusted OR 261 [36-∞]). Allopurinol should be commenced at a dose of 100 mg daily and increased by 100 mg increments until the desired serum uric acid level is attained. Previous reports have shown that allopurinol is commenced at inappropriate doses [79] and that higher doses are associated with an increased incidence of acute events [80]. It is likely that the rapid accumulation of the chemically reactive metabolite oxypurinol when higher doses of allopurinol are commenced increases the risk of SJS/TEN [81],[82]. This drug accumulation hypothesis is further supported by the 4.7 fold increased incidence of allopuri‐ nol-induced SCAR in renal insufficiency [83]. The established indications for allopurinol are treatment of hyperuricemia associated with chronic gout, acute uric acid nephropathy, recurrent uric acid stone formation, enzyme disorders of purine metabolism, and in the management of tumour lysis. Allopurinol is not indicated in the majority of patients with asymptomatic hyperuricemia [84]. However, allopurinol is inappropriately prescribed in up to 86% of cases [85]-[87]. A comparison of allopurinol exposure between the SCAR (1989-1993) and EuroSCAR (1997-2001) studies showed a 2-3 fold increase in exposure for both patients and control subjects, which may be attributed to the increased prescribing of the drug for the treatment of asymptomatic hyperuricemia. The authors of the EuroSCAR study postulate that up to 48 of the 56 cases of allopurinol-induced SJS/TEN could have been prevented if the

Lamotrigine when commenced at high doses can also overwhelm the detoxifying capacity resulting in an increased risk of SJS/TEN and DIHS [88]. The incidence has reduced signifi‐ cantly as a result of the now conventional practice of gradually titrating the dose [89]. Coad‐ ministration of certain drugs can predispose to SCAR by competition for the same enzymebinding site. Reactions to lamotrigine are more common when given in combination with valproic acid as the addition of valproic acid inhibits the clearance of lamotrigine by competing

The role of slow acetylation phenotypes of N-acetyltransferase was thought to confer suscept‐ ibility of sulphonamide-induced SJS/TEN in two small studies [91],[92] but this needs confir‐

A presumptive diagnosis of SJS/TEN is made clinically and is confirmed with a skin biopsy (Figs. 6 & 7). Early lesions demonstrate vacuolar alteration and scattered necrotic keratinocytes in the epidermal layers at the level of the stratum spinosum and the basal cell layer. Later, full thickness epidermal necrosis is evident, which eventuates in the formation of subepidermal

mvRR 2.1 [0.5-9.0], or acute infection in the past 4 weeks [1.2-2.3] [11].

treatment guidelines for prescribing allopurinol were followed.

for glucoronic acid conjugation [90].

mation in larger studies.

**4.7. Diagnosis**

*4.6.3. Pharmacokinetics*

60 Skin Biopsy - Diagnosis and Treatment

Skin tests and oral challenges are contraindicated in SJS/TEN because of the risk of inducing a recurrence of disease. Patch testing has not been investigated extensively. The biggest cohort comprised 22 patients and showed a poor sensitivity of only 9% [96]. Lymphocyte transfor‐ mation tests (LTTs) assesses the proliferation of the patient's peripheral blood T cells cultured

typically shows an interface dermatitis with hydropic degeneration of the basal cell layer [99]. Some exanthems may progress to more severe reactions such as SJS/TEN or DIHS. Generalized bullous fixed drug eruption (GBFDE) features large brownish violaceous patches upon which flaccid blisters arise. These blisters affect only a small percentage of the TBSA. Mucosal involvement is rare and fever is absent. Most patients report a history of a similar local reaction

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 63

Staphylococcal scalded skin syndrome (SSSS) usually affects children under the age of 5 years and patients present with fever, erythema and painful skin, followed by blistering, which is typically accentuated in areas of friction and around orifices [101]. SSSS is caused by the systemic distribution of epidermolytic toxins produced by certain strains of Staphylococci. These toxins cause separation at the level of the stratum granulosum, the upper layer of the epidermis, resulting in very superficial detachment of the skin and blistering[102]. Mucous membrane involvement is rare. The condition usually but not always follows local or systemic staphylococcal infection [103]. Adults are less susceptible as improved renal function allows for better clearance of the toxins. However SSSS has been described in adults who are immu‐ nosuppressed or in renal failure [101]. Toxic shock syndrome (TSS) is caused by elaboration of toxins produced by *Staphylococcus aureus* and *Streptococcus pyogenes* that act as superanti‐ gens, which bind to the variable regions of β chains of antigen receptors on subsets of T cells and cross-link them to the MHC molecules of antigen-presenting cells [104]. This results in activation of large numbers of T cells (5-30%) and the massive release of cytokines including IL-2, TNF, lymphotoxin and IL-1β. TSS is characterised by fever, diffuse red macular rash, hypotension and involvement of ≥3 organs: renal failure, hepatitis, thrombocytopenia, encephalopathy, mucous membrane hyperemia, gastrointestinal involvement with vomiting and diarhhoea. Desquamation occurs after 1-2 weeks and predominantly affects the palms and soles. Approximately 50% of cases are menstrually related due to the prolonged application of absorbent tampons. Notably, 50% of cases of TSS are not associated with menstruation. Nonmenstrual cases of TSS usually complicate the use of barrier contraceptives, surgical and postpartum wound infections, burns, cutaneous lesions, osteomyelitis, and arthritis. Although

most cases of TSS occur in women, about 25% of non-menstrual cases occur in men.

Autoimmune bullous diseases need to be considered in the differential diagnosis of SJS/ TEN. These conditions, in contrast to SJS/TEN, usually have a chronic course and are characterized by acantholysis on histopathology and immunoglobulin deposition on DIF. Drug-induced linear IgA bullous dermatosis can produce an acute extensive eruption of target-like lesions, pruritic urticarial plaques and tense bullae on the trunk and limbs [105]. Vancomycin is the most commonly implicated drug. In contrast to SJS, mucosal le‐ sions are rare and DIF shows linear deposition of IgA at the basement membrane zone. Paraneoplastic pemphigus (PNP) is a chronic disease characterized by severe and intract‐ able oral mucositis and a generalized polymorphous blistering eruption in association with an occult or overt malignancy, especially, lymphoma and Castleman's disease [106], [107]. Conjunctivitis is common and respiratory and gastrointestinal surfaces may be in‐ volved. DIF shows deposition of IgG and complement (C3) within the epidermal intercel‐ lular spaces and along the epidermal basement membrane. Drug-induced pemphigus is

or fixed drug eruption [100].

**Figure 7.** High power view of a skin biopsy from a patient with SJS shows necrosis of keratinocytes, and vacuolar de‐ generation of the basal cell layer. A sparse lymphocytic infiltrate is present at the dermoepidermal junction and dis‐ plays satellitosis or clustering around dying basal cells (Hematoxylin-eosin, original magnification x200).

in the presence of a suspected drug for 6 days by measuring the incorporation of 3 H-thymidine during DNA synthesis. The result is expressed as a stimulation index, which is the ratio of cell proliferation with antigen and without antigen. The sensitivity of LTTs in SJS/TEN is greatly improved if the test is performed within 1 week of the onset of disease but becomes negative by 6 weeks [97]. This may be attributed to loss of regulatory T cell function in the acute phase, which is then restored upon recovery [55]. Recently, a new cytotoxicity assay combining the measurement of expression of the degranulation marker, CD107a, using flow cytometry and the release of the serine protease, granzyme B by Elispot after incubating the patient's peripheral blood mononuclear cells with the suspected drug for 3 days [98]. The test has very good specificity with all of the 16 controls having a negative test and good sensitivity with 10 of the 12 patients having a positive result. One role of these in vitro tests is to determine the culprit drug when more than one drug is suspected.

#### **4.9. Differential Diagnosis**

SJS/TEN is differentiated from other conditions on the basis of the acute onset of disease, the presence of targetoid and vesiculobullous lesions, sloughing of the epidermis, severe mucosal involvement, the histologic finding of full thickness epidermal necrosis, and a negative DIF. In EM major, erosive mucous membrane involvement is present but in contrast to SJS, the patient has typical target lesions mainly affecting the extremities and it is often induced by acute or recurrent HSV infection. The clinical manifestations of drug-induced maculopapular exanthems (MPE) are variable and often polymorphic and lesions may have a target-like appearance. Fever may be present but mucosal involvement is absent. The histopathology typically shows an interface dermatitis with hydropic degeneration of the basal cell layer [99]. Some exanthems may progress to more severe reactions such as SJS/TEN or DIHS. Generalized bullous fixed drug eruption (GBFDE) features large brownish violaceous patches upon which flaccid blisters arise. These blisters affect only a small percentage of the TBSA. Mucosal involvement is rare and fever is absent. Most patients report a history of a similar local reaction or fixed drug eruption [100].

Staphylococcal scalded skin syndrome (SSSS) usually affects children under the age of 5 years and patients present with fever, erythema and painful skin, followed by blistering, which is typically accentuated in areas of friction and around orifices [101]. SSSS is caused by the systemic distribution of epidermolytic toxins produced by certain strains of Staphylococci. These toxins cause separation at the level of the stratum granulosum, the upper layer of the epidermis, resulting in very superficial detachment of the skin and blistering[102]. Mucous membrane involvement is rare. The condition usually but not always follows local or systemic staphylococcal infection [103]. Adults are less susceptible as improved renal function allows for better clearance of the toxins. However SSSS has been described in adults who are immu‐ nosuppressed or in renal failure [101]. Toxic shock syndrome (TSS) is caused by elaboration of toxins produced by *Staphylococcus aureus* and *Streptococcus pyogenes* that act as superanti‐ gens, which bind to the variable regions of β chains of antigen receptors on subsets of T cells and cross-link them to the MHC molecules of antigen-presenting cells [104]. This results in activation of large numbers of T cells (5-30%) and the massive release of cytokines including IL-2, TNF, lymphotoxin and IL-1β. TSS is characterised by fever, diffuse red macular rash, hypotension and involvement of ≥3 organs: renal failure, hepatitis, thrombocytopenia, encephalopathy, mucous membrane hyperemia, gastrointestinal involvement with vomiting and diarhhoea. Desquamation occurs after 1-2 weeks and predominantly affects the palms and soles. Approximately 50% of cases are menstrually related due to the prolonged application of absorbent tampons. Notably, 50% of cases of TSS are not associated with menstruation. Nonmenstrual cases of TSS usually complicate the use of barrier contraceptives, surgical and postpartum wound infections, burns, cutaneous lesions, osteomyelitis, and arthritis. Although most cases of TSS occur in women, about 25% of non-menstrual cases occur in men.

in the presence of a suspected drug for 6 days by measuring the incorporation of 3

plays satellitosis or clustering around dying basal cells (Hematoxylin-eosin, original magnification x200).

culprit drug when more than one drug is suspected.

**4.9. Differential Diagnosis**

62 Skin Biopsy - Diagnosis and Treatment

during DNA synthesis. The result is expressed as a stimulation index, which is the ratio of cell proliferation with antigen and without antigen. The sensitivity of LTTs in SJS/TEN is greatly improved if the test is performed within 1 week of the onset of disease but becomes negative by 6 weeks [97]. This may be attributed to loss of regulatory T cell function in the acute phase, which is then restored upon recovery [55]. Recently, a new cytotoxicity assay combining the measurement of expression of the degranulation marker, CD107a, using flow cytometry and the release of the serine protease, granzyme B by Elispot after incubating the patient's peripheral blood mononuclear cells with the suspected drug for 3 days [98]. The test has very good specificity with all of the 16 controls having a negative test and good sensitivity with 10 of the 12 patients having a positive result. One role of these in vitro tests is to determine the

**Figure 7.** High power view of a skin biopsy from a patient with SJS shows necrosis of keratinocytes, and vacuolar de‐ generation of the basal cell layer. A sparse lymphocytic infiltrate is present at the dermoepidermal junction and dis‐

SJS/TEN is differentiated from other conditions on the basis of the acute onset of disease, the presence of targetoid and vesiculobullous lesions, sloughing of the epidermis, severe mucosal involvement, the histologic finding of full thickness epidermal necrosis, and a negative DIF. In EM major, erosive mucous membrane involvement is present but in contrast to SJS, the patient has typical target lesions mainly affecting the extremities and it is often induced by acute or recurrent HSV infection. The clinical manifestations of drug-induced maculopapular exanthems (MPE) are variable and often polymorphic and lesions may have a target-like appearance. Fever may be present but mucosal involvement is absent. The histopathology

H-thymidine

Autoimmune bullous diseases need to be considered in the differential diagnosis of SJS/ TEN. These conditions, in contrast to SJS/TEN, usually have a chronic course and are characterized by acantholysis on histopathology and immunoglobulin deposition on DIF. Drug-induced linear IgA bullous dermatosis can produce an acute extensive eruption of target-like lesions, pruritic urticarial plaques and tense bullae on the trunk and limbs [105]. Vancomycin is the most commonly implicated drug. In contrast to SJS, mucosal le‐ sions are rare and DIF shows linear deposition of IgA at the basement membrane zone. Paraneoplastic pemphigus (PNP) is a chronic disease characterized by severe and intract‐ able oral mucositis and a generalized polymorphous blistering eruption in association with an occult or overt malignancy, especially, lymphoma and Castleman's disease [106], [107]. Conjunctivitis is common and respiratory and gastrointestinal surfaces may be in‐ volved. DIF shows deposition of IgG and complement (C3) within the epidermal intercel‐ lular spaces and along the epidermal basement membrane. Drug-induced pemphigus is usually triggered by thiol drugs in genetically susceptible individuals [108]. These drugs, such as penicillamine, captopril and enalapril, directly interact with the epidermis and cause acantholysis and a superficial blistering eruption with crusts and erosions without mucosal involvement resembling pemphigus foliaceus (PF) [109]. However, in contrast to PF, which is mediated by antibodies against desmoglein-3, DIF may be negative in druginduced pemphigus. Non-thiol drugs can cause disease indistinguishable from pemphi‐ gus vulgaris (PV). These cases of drug-triggered pemphigus, like PV are chronic with autoantibodies formed against desmoglein-3 [110]. Hence a flaccid blistering eruption with mucosal involvement occurs, and DIF shows IgG and C3 deposition in the epider‐ mal intercellular spaces. Bullous pemphigoid (BP) is a chronic disease that is typified by a tense bullous eruption that primarily affects individuals in the fifth through seventh decades of life. Drugs, especially diuretics such as furosemide and spironolactone, can in‐ duce BP [111] and should be considered when the condition occurs in a young patient and the course is more abrupt [112]. Unlike in SJS/TEN, fever is absent, mucosal lesions are usually absent, and DIF reveals IgG and C3 linear deposition along the epidermal basement membrane [113].

**Bullous disease Fever Mucositis Rash DIF Onset Other notable**

Targetoid lesions Vesicles, bullae Erosions, detachment

Target lesions

Pleomorphic

Large bullae

Skin tenderness Periorificial crusting

Desquamation of palms and soles


rash

Bullae

Crusts

Bullae

pustules Erythroderma

Flaccid bullae

Erosions, detachment



SJS/TEN + + Erythroderma

EM Major + + Acral

Drug-induced MPE +/- - Variable

GBFDE - - Brown patches

SSSS + - Erythroderma

TSS + + Diffuse red macular

PNP - + Polymorphous

AGVHD + + Morbilliform rash

AGEP + +/- Small nonfollicular

**Table 2.** The differential diagnosis of SJS/TEN

Drug-induced linear IgA dermatosis

Drug-induced pemphigus

Drug-triggered pemphigus

**features**

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 65

spreads

recurrences

reaction Small % TBSA

therapy

Pruritus

Adults with chronic renal failure and on immunosuppressive

Multiple organ failure





+ Gradual Thiol drugs

+ Gradual Non-thiol drugs


+ Gradual


proximal upper limbs and face and then



Acute graft versus host disease (AGVHD) shares many of the same clinical, pathologic and immunologic features as SJS/TEN. Both conditions are mediated by cytotoxic T cells, which results in epidermal necrosis and keratinolysis [114],[115]. Furthermore, bone marrow transplantation (BMT) patients receive medications that can trigger SJS/TEN. AGVHD generally occurs 4 weeks after stem cell transplantation. Patients describe a sensation of skin pain and itching followed by a morbilliform rash that in severe cases becomes generalized with diffuse areas of epidermal necrosis [116]. Mucositis is usually present. AGVHD frequently begins acrally and spreads proximally in contrast to TEN, which begins on the trunk and spreads distally. Also, the early exanthem of AGVHD has a folliculocentric distribution [117].

AGEP is characterized by fever and as the disease progresses, widespread erosions mimicking SJS/TEN may be evident [118]. Mucous membrane involvement is unusual and if present is mild.

SJS/TEN, Stevens-Johnson syndrome/toxic epidermal necrolysis; EM, erythema multiforme; MPE, maculopapular exanthem; GBFDE, generalized bullous fixed drug eruption; SSSS, staphylococcal scalded skin syndrome; TSS, toxic shock syndrome; PNP, paraneoplastic pemphigus; AGVHD, acute graft versus host disease; AGEP, acute generalized exanthematous pustulosis

#### **4.10. Treatment**

#### *4.10.1. Supportive care*

Immediate discontinuation of the culprit drug is mandatory to reduce mortality [119]. As the management of TEN is similar to that of extensive burns, a transfer to a burns unit reduces morbidity and mortality. The largest trial showed a mortality rate of 29.8% after transfer to a burns unit compared to 51.4% (p <.05) after 7 days [120]. The unit has expertise in providing


**Table 2.** The differential diagnosis of SJS/TEN

usually triggered by thiol drugs in genetically susceptible individuals [108]. These drugs, such as penicillamine, captopril and enalapril, directly interact with the epidermis and cause acantholysis and a superficial blistering eruption with crusts and erosions without mucosal involvement resembling pemphigus foliaceus (PF) [109]. However, in contrast to PF, which is mediated by antibodies against desmoglein-3, DIF may be negative in druginduced pemphigus. Non-thiol drugs can cause disease indistinguishable from pemphi‐ gus vulgaris (PV). These cases of drug-triggered pemphigus, like PV are chronic with autoantibodies formed against desmoglein-3 [110]. Hence a flaccid blistering eruption with mucosal involvement occurs, and DIF shows IgG and C3 deposition in the epider‐ mal intercellular spaces. Bullous pemphigoid (BP) is a chronic disease that is typified by a tense bullous eruption that primarily affects individuals in the fifth through seventh decades of life. Drugs, especially diuretics such as furosemide and spironolactone, can in‐ duce BP [111] and should be considered when the condition occurs in a young patient and the course is more abrupt [112]. Unlike in SJS/TEN, fever is absent, mucosal lesions are usually absent, and DIF reveals IgG and C3 linear deposition along the epidermal

Acute graft versus host disease (AGVHD) shares many of the same clinical, pathologic and immunologic features as SJS/TEN. Both conditions are mediated by cytotoxic T cells, which results in epidermal necrosis and keratinolysis [114],[115]. Furthermore, bone marrow transplantation (BMT) patients receive medications that can trigger SJS/TEN. AGVHD generally occurs 4 weeks after stem cell transplantation. Patients describe a sensation of skin pain and itching followed by a morbilliform rash that in severe cases becomes generalized with diffuse areas of epidermal necrosis [116]. Mucositis is usually present. AGVHD frequently begins acrally and spreads proximally in contrast to TEN, which begins on the trunk and spreads distally. Also, the early exanthem of AGVHD has a folliculocentric distribution [117].

AGEP is characterized by fever and as the disease progresses, widespread erosions mimicking SJS/TEN may be evident [118]. Mucous membrane involvement is unusual and if present is

SJS/TEN, Stevens-Johnson syndrome/toxic epidermal necrolysis; EM, erythema multiforme; MPE, maculopapular exanthem; GBFDE, generalized bullous fixed drug eruption; SSSS, staphylococcal scalded skin syndrome; TSS, toxic shock syndrome; PNP, paraneoplastic pemphigus; AGVHD, acute graft versus host disease; AGEP, acute generalized exanthematous

Immediate discontinuation of the culprit drug is mandatory to reduce mortality [119]. As the management of TEN is similar to that of extensive burns, a transfer to a burns unit reduces morbidity and mortality. The largest trial showed a mortality rate of 29.8% after transfer to a burns unit compared to 51.4% (p <.05) after 7 days [120]. The unit has expertise in providing

basement membrane [113].

64 Skin Biopsy - Diagnosis and Treatment

mild.

pustulosis

**4.10. Treatment**

*4.10.1. Supportive care*

analgesia, maintaining fluid and electrolyte balance and preventing and treating superinfec‐ tion. It has been recently noted that in contrast to burns, TEN affects the epidermis and hence fluid and electrolyte requirements are less than for burns of the same extent [121]; initial administration of 2 ml/kg/%TBSA is usually sufficient [122]. Additional nutritional require‐ ments result from loss of nitrogen and energy from the wound exudate, the hypermetabolic response of TEN and sepsis and the promotion of wound healing. However, these require‐ ments may lower than in burns, with one study in the paediatric population suggesting that that patients with TENS require 22% fewer calories per day than patients with burns. A formula was subsequently developed: calorie requirement = baseline weight (kg) x 24.6 + wound size (%TBSA) x 4.1 + 940 [123]. Enteral or total parenteral nutrition should be considered in patients unable to ingest food. Nasogastric feeding should be cautiously initiated because of gastroin‐ testinal involvement from TEN and the difficulties in placing a nasogastric tube in the presence of a oropharyngeal involvement [124]. Room temperature should be adjusted to 30-32ºC or heat-air body warmers should be used to prevent excessive caloric expenditure due to epidermal loss [25].

*4.10.2. Corticosteroids*

The role of corticosteroids in the treatment of SJS/TEN is controversial. Corticosteroids given 48 hours or more prior to admission are associated with an increase incidence of infection, length of hospital admission, and mortality in children and adults [132]-[134]. A study in 1986 of 30 patients with TEN with an average TBSA involvement > 80% were equally divided into those receiving supportive care alone and those receiving dexamethasone at varying doses [135]. Although the incidence of sepsis was not significant different between the groups, the survival following onset of sepsis was less in the corticosteroid treated group. The use of corticosteroids doubled the rate of mortality (66% versus 33%). Corticosteroids do not prevent SJS/TEN from occurring and have no effect on arresting disease progression [136],[137]. A retrospective analysis of 281 patients from the EuroSCAR study found no benefit from

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 67

The poor outcomes may have resulted from inadequate doses and the delay in the initiation of corticosteroid therapy. In a prospective study of 16 children with SJS in 1997, 10 received methylprednisolone (4 mg/kg/daily) within 3 days of the onset of rash whilst 6 received supportive care only; corticosteroids were associated with decreased length of fever and duration of skin eruption [138]. The use of pulsed IV corticosteroids has been shown in retrospective reviews to reduce mortality [139]-[141]. The initiation of IV methylprednisolone 500-1000 mg/daily for 3-4 days may also prevent ocular complications of cicatrization and preservation of visual acuity [142]. The benefits of early pulsed therapy with IV corticosteroids

The current level of evidence suggests that high dose corticosteroids may be beneficial if commenced early in the course of disease with vigilant monitoring for emergence of infection. However, no definitive conclusion can be drawn from this current level of evidence and prospective trials with well defined protocols are required to define the role of corticosteroids

The rationale for the use of IVIg was based on its ability in vitro to block Fas and subsequently FasL-mediated apoptosis of keratinocytes [51]. The beneficial role of IVIg in SJS/TEN has been demonstrated in retrospective studies. The largest such study to date comprised 48 patients with TEN with a 44.8% mean TBSA recruited from centres across Europe and the United States. Treatment with IVIg resulted in a more rapid cessation of epidermal detachment and a survival rate of 88%. The authors subsequently recommended a dose of 1 g/kg/daily for 3 days [143]. Studies have also demonstrated benefit when investigators have compared the rates of mortality following the use of IVIg with the pre-treatment estimate using SCORTEN. For example, Campione et al, found that 400 mg/kg/daily for 5 days of IVIg resulted in a mortality rate of 10%, significantly lower that the 35% predicted using SCORTEN [144]. Metry et al,

In 2006, a retrospective study found that the use of IVIg at a total dose of 2.8 g/kg/daily in 23 patients resulted in a marked difference in mortality compared to 8 patients who received

showed that the benefit of IVIg extended to the paediatric population [145].

corticosteroids or IVIg compared to supportive care alone.

need to be further evaluated in randomized control trials.

in the treatment of SJS/TEN.

*4.10.3. Intravenous Immunoglobulin (IVIg)*

The optimal approach to wound management has not been determined and will therefore vary between specialty units. The contrasting measures of surgical debridement with whirlpool therapy to remove necrotic epidermis, and anti-shear wound care [125], in which detached skin is left in situ to act as a biological dressing [126], both have equivalent rates of reepithelialization and survival. Non-adherent nanocrystalline-containing gauzes are being increasingly used because of their broad antimicrobial effects [127],[128]. This obviates the need for topical silver sulphadiazine because of the strong association between sulphonamides and SJS/TEN. There is also a trend in the use of biosynthetic skin substitutes in place of porcine xenograft and human allograft cadaveric skin because of reduced pain and improved mobili‐ zation in elderly patients [129].

Prophylactic antibiotics are not advised as they predispose to the emergence of resistant organisms [121]. Hence, repeated cultures of the skin, blood and other sites guide the need for antibiotic therapy. Sterile handling and reverse-isolation procedures are essential in the prevention of nosocomial infection [130].

Ophthalmologic consultation is mandatory in SJS/TEN and the combination of aggressive lubrication, topical antibiotics, topical corticosteroids, and lysis of adhesions with a glass rod is implemented immediately but has only a modest effect on the long term ocular complications. Recently, the application of amniotic membranes has proved effective in preserving visual acuity and an intact ocular surface [37]. The benefit may be derived from creating a physical barrier between inflamed and denuded mucosal surfaces that minimiz‐ es the formation of adhesions. The membrane may also have antiinflammatory and antifibrotic effects [131].

Other supportive measures include hygienic mouthwashes and topical oral anaesthetics, and monitoring for urinary retention.

#### *4.10.2. Corticosteroids*

analgesia, maintaining fluid and electrolyte balance and preventing and treating superinfec‐ tion. It has been recently noted that in contrast to burns, TEN affects the epidermis and hence fluid and electrolyte requirements are less than for burns of the same extent [121]; initial administration of 2 ml/kg/%TBSA is usually sufficient [122]. Additional nutritional require‐ ments result from loss of nitrogen and energy from the wound exudate, the hypermetabolic response of TEN and sepsis and the promotion of wound healing. However, these require‐ ments may lower than in burns, with one study in the paediatric population suggesting that that patients with TENS require 22% fewer calories per day than patients with burns. A formula was subsequently developed: calorie requirement = baseline weight (kg) x 24.6 + wound size (%TBSA) x 4.1 + 940 [123]. Enteral or total parenteral nutrition should be considered in patients unable to ingest food. Nasogastric feeding should be cautiously initiated because of gastroin‐ testinal involvement from TEN and the difficulties in placing a nasogastric tube in the presence of a oropharyngeal involvement [124]. Room temperature should be adjusted to 30-32ºC or heat-air body warmers should be used to prevent excessive caloric expenditure due to

The optimal approach to wound management has not been determined and will therefore vary between specialty units. The contrasting measures of surgical debridement with whirlpool therapy to remove necrotic epidermis, and anti-shear wound care [125], in which detached skin is left in situ to act as a biological dressing [126], both have equivalent rates of reepithelialization and survival. Non-adherent nanocrystalline-containing gauzes are being increasingly used because of their broad antimicrobial effects [127],[128]. This obviates the need for topical silver sulphadiazine because of the strong association between sulphonamides and SJS/TEN. There is also a trend in the use of biosynthetic skin substitutes in place of porcine xenograft and human allograft cadaveric skin because of reduced pain and improved mobili‐

Prophylactic antibiotics are not advised as they predispose to the emergence of resistant organisms [121]. Hence, repeated cultures of the skin, blood and other sites guide the need for antibiotic therapy. Sterile handling and reverse-isolation procedures are essential in the

Ophthalmologic consultation is mandatory in SJS/TEN and the combination of aggressive lubrication, topical antibiotics, topical corticosteroids, and lysis of adhesions with a glass rod is implemented immediately but has only a modest effect on the long term ocular complications. Recently, the application of amniotic membranes has proved effective in preserving visual acuity and an intact ocular surface [37]. The benefit may be derived from creating a physical barrier between inflamed and denuded mucosal surfaces that minimiz‐ es the formation of adhesions. The membrane may also have antiinflammatory and

Other supportive measures include hygienic mouthwashes and topical oral anaesthetics, and

epidermal loss [25].

66 Skin Biopsy - Diagnosis and Treatment

zation in elderly patients [129].

antifibrotic effects [131].

monitoring for urinary retention.

prevention of nosocomial infection [130].

The role of corticosteroids in the treatment of SJS/TEN is controversial. Corticosteroids given 48 hours or more prior to admission are associated with an increase incidence of infection, length of hospital admission, and mortality in children and adults [132]-[134]. A study in 1986 of 30 patients with TEN with an average TBSA involvement > 80% were equally divided into those receiving supportive care alone and those receiving dexamethasone at varying doses [135]. Although the incidence of sepsis was not significant different between the groups, the survival following onset of sepsis was less in the corticosteroid treated group. The use of corticosteroids doubled the rate of mortality (66% versus 33%). Corticosteroids do not prevent SJS/TEN from occurring and have no effect on arresting disease progression [136],[137]. A retrospective analysis of 281 patients from the EuroSCAR study found no benefit from corticosteroids or IVIg compared to supportive care alone.

The poor outcomes may have resulted from inadequate doses and the delay in the initiation of corticosteroid therapy. In a prospective study of 16 children with SJS in 1997, 10 received methylprednisolone (4 mg/kg/daily) within 3 days of the onset of rash whilst 6 received supportive care only; corticosteroids were associated with decreased length of fever and duration of skin eruption [138]. The use of pulsed IV corticosteroids has been shown in retrospective reviews to reduce mortality [139]-[141]. The initiation of IV methylprednisolone 500-1000 mg/daily for 3-4 days may also prevent ocular complications of cicatrization and preservation of visual acuity [142]. The benefits of early pulsed therapy with IV corticosteroids need to be further evaluated in randomized control trials.

The current level of evidence suggests that high dose corticosteroids may be beneficial if commenced early in the course of disease with vigilant monitoring for emergence of infection. However, no definitive conclusion can be drawn from this current level of evidence and prospective trials with well defined protocols are required to define the role of corticosteroids in the treatment of SJS/TEN.

#### *4.10.3. Intravenous Immunoglobulin (IVIg)*

The rationale for the use of IVIg was based on its ability in vitro to block Fas and subsequently FasL-mediated apoptosis of keratinocytes [51]. The beneficial role of IVIg in SJS/TEN has been demonstrated in retrospective studies. The largest such study to date comprised 48 patients with TEN with a 44.8% mean TBSA recruited from centres across Europe and the United States. Treatment with IVIg resulted in a more rapid cessation of epidermal detachment and a survival rate of 88%. The authors subsequently recommended a dose of 1 g/kg/daily for 3 days [143]. Studies have also demonstrated benefit when investigators have compared the rates of mortality following the use of IVIg with the pre-treatment estimate using SCORTEN. For example, Campione et al, found that 400 mg/kg/daily for 5 days of IVIg resulted in a mortality rate of 10%, significantly lower that the 35% predicted using SCORTEN [144]. Metry et al, showed that the benefit of IVIg extended to the paediatric population [145].

In 2006, a retrospective study found that the use of IVIg at a total dose of 2.8 g/kg/daily in 23 patients resulted in a marked difference in mortality compared to 8 patients who received supportive therapy alone despite the absence of a difference in SCORTEN between the two groups. The mortality rate was 26% in the patient group receiving IVIg and 75% in the group receiving supportive care only. This difference, however, was not statistically significant. A study by Yang et al, showed a lower than predicted mortality rate for patients given IVIg and corticosteroids and a higher than expected mortality rate for those receiving corticosteroids alone. This difference was not statistically significant [146].

care but without PE [166]. There is insufficient evidence at this stage to support the use of PE

Severe Cutaneous Adverse Reactions http://dx.doi.org/10.5772/54820 69

TNF is thought to be upregulated in TEN and immunohistochemistry has demonstrated increased levels of TNF from 23 patients as compared with controls [167]. Thalidomide, a potent inhibitor of TNF, was found in a double blinded randomized placebo controlled trial to be lethal in 10 of 12 patients compared with 3 of 10 control subjects. The exact mechanism underlying these fatalities is unknown but the drug is firmly contraindicated in SJS/TEN.

Infliximab and eternecept has been shown to be beneficial in a small number of case reports [168]-[173]. The drug was usually administered late in the course of disease and therefore its

Strategies have been explored to overcome the diminished detoxifying capacity of abnormal inherent metabolic pathways evident in a proportion of patients with SJS/TEN. Administration of N-acetylcysteine enhances the oxidant buffering capacity of glutathione, which enhances the detoxification of a range of drugs, as well as inhibiting NF-ĸB. Two case reports have shown a beneficial response but larger studies are clearly required before it is readily applied in clinical

In addition to the restricted use of the same medication, structurally similar drugs should also be avoided. The aromatic anticonvulsants carbamazepine, phenytoin and phenobarbitol cross react with one another. Cross reactivity resulting in SJS/TEN can also occur across different classes of beta-lactam antibiotics, such as penicillins, cephalosporins and carbapenems [176]. Administration of a structurally related drug can also result in different reactions. One case report described a patient with ceftriaxone-induced TEN who developed immediate anaphy‐

The risk of SJS/TEN with structurally distinct agents within the same class of drug is less clear. For example, the cross reactivity between a priopionic acid NSAID and an enolic acid NSAID is unknown. The safest practice is to restrict all NSAIDs following NSAID-induced SJS/TEN.

The term hypersensitivity syndrome has been used for decades to describe a cutaneous drug reaction accompanied by involvement of internal organs. In 1938, Merritt and Putnam described a toxic reaction to phenytoin characterized by exfoliative dermatitis, fever and

laxis following the administration of piperacillin/tazobactam [177].

**5. Drug induced hypersensitivity syndrome**

benefit is not clear and requires case-control studies to further elucidate its role.

in preference to other adjunctive measures.

*4.10.6. Anti-TNF therapy*

*4.10.7. N-acetylcysteine*

practice [174],[175].

**5.1. Nosology**

*4.10.8. Restricted use of related medications*

Despite the initial preponderance of evidence favouring the use of IVIG in SJS/TEN, a few published reports have not demonstrated any benefit. Most of these studies comparing the use of IVIg with supportive care alone used doses less than the recommended 2-3 g/kg [147]-[150]. The largest restrospective analysis on the use of IVIg derived from the EuroSCAR study and published in 2008 included 109 patients with TEN, 136 with SJS/TEN overlap, and 134 with SJS found that IVIg administered at a dose of 1.9 g/kg conferred an OR of 1.4 when compared to the use of supportive measures alone. This study involved the use of lower than recom‐ mended doses of IVIg and the patients from the IVIg group tended to have a greater TBSA involvement [151]. A controlled observational study in an intensive care unit in a French dermatology department of 34 patients who presented at a mean of 4.3 days after the onset of TEN revealed a higher mortality rate than that predicted by SCORTEN when 2g/kg of IVIg was administered within 2 days of admission [85].

Randomized control studies are required using sufficient doses of IVIg to characterize its benefit in not only reducing mortality but also arresting the rate of progression and hastening the rate of re-epithelialization. However, the evidence thus far, is not robust as an adjunctive immunomodulatory therapy in the treatment of SJS/TEN.

## *4.10.4. C yclosporine*

Cyclosporine inhibits CD8 activation and subsequent release of granulysin, granzyme and perforin as well as inhibiting the proapoptotic effect of NF-ĸB. Several case and case series reports have shown arrest of disease progression and shorter time to re-epithelialization with doses varying from 3-10 mg/kg/daily for a period ranging from 8 days to several weeks [152] [153]-[161]. The study by Arevalo et al, showed that outcomes for 10 patients treated with cyclosporin was superior to 6 patients treated with cyclophosphamide and corticosteroids with respect to re-epithelialization, disease progression and death [157]. However, randomized control studies are required to better define its benefits, the appropriate dose and duration of therapy. Furthermore, no studies have been published to date evaluating the efficacy of using both IVIg and cyclosporine but may be worthwhile considering as different pathways involved in the pathogenesis of SJS/TEN are targeted.

#### *4.10.5. Plasmapheresis*

Plasmapheresis (PE) has been reported to be beneficial in several case reports and series in patients with TEN based on the principle that the drug, drug metabolite or cytotoxic mediator is removed from the circulation [162]-[165]. One report from Sweden showed no benefit from PE in eight patients compared with patients from other studies who received similar support care but without PE [166]. There is insufficient evidence at this stage to support the use of PE in preference to other adjunctive measures.

#### *4.10.6. Anti-TNF therapy*

supportive therapy alone despite the absence of a difference in SCORTEN between the two groups. The mortality rate was 26% in the patient group receiving IVIg and 75% in the group receiving supportive care only. This difference, however, was not statistically significant. A study by Yang et al, showed a lower than predicted mortality rate for patients given IVIg and corticosteroids and a higher than expected mortality rate for those receiving corticosteroids

Despite the initial preponderance of evidence favouring the use of IVIG in SJS/TEN, a few published reports have not demonstrated any benefit. Most of these studies comparing the use of IVIg with supportive care alone used doses less than the recommended 2-3 g/kg [147]-[150]. The largest restrospective analysis on the use of IVIg derived from the EuroSCAR study and published in 2008 included 109 patients with TEN, 136 with SJS/TEN overlap, and 134 with SJS found that IVIg administered at a dose of 1.9 g/kg conferred an OR of 1.4 when compared to the use of supportive measures alone. This study involved the use of lower than recom‐ mended doses of IVIg and the patients from the IVIg group tended to have a greater TBSA involvement [151]. A controlled observational study in an intensive care unit in a French dermatology department of 34 patients who presented at a mean of 4.3 days after the onset of TEN revealed a higher mortality rate than that predicted by SCORTEN when 2g/kg of IVIg

Randomized control studies are required using sufficient doses of IVIg to characterize its benefit in not only reducing mortality but also arresting the rate of progression and hastening the rate of re-epithelialization. However, the evidence thus far, is not robust as an adjunctive

Cyclosporine inhibits CD8 activation and subsequent release of granulysin, granzyme and perforin as well as inhibiting the proapoptotic effect of NF-ĸB. Several case and case series reports have shown arrest of disease progression and shorter time to re-epithelialization with doses varying from 3-10 mg/kg/daily for a period ranging from 8 days to several weeks [152] [153]-[161]. The study by Arevalo et al, showed that outcomes for 10 patients treated with cyclosporin was superior to 6 patients treated with cyclophosphamide and corticosteroids with respect to re-epithelialization, disease progression and death [157]. However, randomized control studies are required to better define its benefits, the appropriate dose and duration of therapy. Furthermore, no studies have been published to date evaluating the efficacy of using both IVIg and cyclosporine but may be worthwhile considering as different pathways involved

Plasmapheresis (PE) has been reported to be beneficial in several case reports and series in patients with TEN based on the principle that the drug, drug metabolite or cytotoxic mediator is removed from the circulation [162]-[165]. One report from Sweden showed no benefit from PE in eight patients compared with patients from other studies who received similar support

alone. This difference was not statistically significant [146].

was administered within 2 days of admission [85].

in the pathogenesis of SJS/TEN are targeted.

*4.10.4. C yclosporine*

68 Skin Biopsy - Diagnosis and Treatment

*4.10.5. Plasmapheresis*

immunomodulatory therapy in the treatment of SJS/TEN.

TNF is thought to be upregulated in TEN and immunohistochemistry has demonstrated increased levels of TNF from 23 patients as compared with controls [167]. Thalidomide, a potent inhibitor of TNF, was found in a double blinded randomized placebo controlled trial to be lethal in 10 of 12 patients compared with 3 of 10 control subjects. The exact mechanism underlying these fatalities is unknown but the drug is firmly contraindicated in SJS/TEN.

Infliximab and eternecept has been shown to be beneficial in a small number of case reports [168]-[173]. The drug was usually administered late in the course of disease and therefore its benefit is not clear and requires case-control studies to further elucidate its role.

#### *4.10.7. N-acetylcysteine*

Strategies have been explored to overcome the diminished detoxifying capacity of abnormal inherent metabolic pathways evident in a proportion of patients with SJS/TEN. Administration of N-acetylcysteine enhances the oxidant buffering capacity of glutathione, which enhances the detoxification of a range of drugs, as well as inhibiting NF-ĸB. Two case reports have shown a beneficial response but larger studies are clearly required before it is readily applied in clinical practice [174],[175].

## *4.10.8. Restricted use of related medications*

In addition to the restricted use of the same medication, structurally similar drugs should also be avoided. The aromatic anticonvulsants carbamazepine, phenytoin and phenobarbitol cross react with one another. Cross reactivity resulting in SJS/TEN can also occur across different classes of beta-lactam antibiotics, such as penicillins, cephalosporins and carbapenems [176]. Administration of a structurally related drug can also result in different reactions. One case report described a patient with ceftriaxone-induced TEN who developed immediate anaphy‐ laxis following the administration of piperacillin/tazobactam [177].

The risk of SJS/TEN with structurally distinct agents within the same class of drug is less clear. For example, the cross reactivity between a priopionic acid NSAID and an enolic acid NSAID is unknown. The safest practice is to restrict all NSAIDs following NSAID-induced SJS/TEN.
