Epidemiology of cutaneous adverse drug reactions

Epidemiologic investigation of cutaneous adverse drug reactions (cADRs) is important in order to evaluate their impact on dermatology and health care in general as well as their burden on affected patients. Few epidemiologic studies have been performed on frequent non-life-threatening cADR, including reactions of both delayed and immediate hypersensitivity, such as maculopapular exanthema (MPE), fixed drug eruption, and urticaria. Concerning rare but life-threatening severe cutaneous adverse reactions, e.g., toxic epidermal necrolysis (TEN), Stevens-Johnson syndrome (SJS), acute generalized exanthematous pustulosis (AGEP), and drug reaction with eosinophilia and systemic symptoms (DRESS), several epidemiologic studies have been performed to date, some of which are still ongoing. Such studies enable the calculation of reliable incidence rates and demographic data, and also allow researchers to perform risk estimation for drugs. The spectrum of drugs causing cADR differs substantially when separating the various clinical conditions. Whereas antibiotics are by far the most frequent inducers of milder cADRs, like MPE, they have a much lower risk of inducing SJS/TEN, for which "high-risk" drugs are anti-infective sulfonamides, allopurinol, certain anti-epileptic drugs, nevirapine, and non-steroidal anti-inflammatory drugs (NSAIDs) of the oxicam-type. In contrast, AGEP is predominantly caused by the antibiotics pristinamycin and aminopenicillins, followed by quinolones, (hydroxy-)chloroquine, and sulfonamides. DRESS can be induced by a number of drugs known to cause SJS/TEN, such as certain antiepileptics and allopurinol, but also other medications (e.g., minocyclin).

Drug reaction with eosinophilia and systemic symptoms (DRESS): an original multisystem adverse drug reaction. Results from the prospective RegiSCAR study

BACKGROUND

Cases of severe drug hypersensitivity, demonstrating a variable spectrum of cutaneous and systemic involvement, are reported under various names, especially drug reaction with eosinophilia and systemic symptoms (DRESS). Case definition and overlap with other severe cutaneous adverse reactions (SCAR) are debated.

OBJECTIVES

To analyse the spectrum of signs and symptoms of DRESS and distribution of causative drugs in a large multicentre series.

PATIENTS AND METHODS

RegiSCAR, a multinational registry of SCAR, prospectively enrolled 201 potential cases from 2003 to mid-2009. Using a standardized scoring system, 117 cases were validated as showing probable or definite DRESS.

RESULTS

The male/female ratio was 0.80; females were borderline significantly younger than males. Next to the ubiquitous exanthema, the main features were eosinophilia (95%), visceral involvement (91%), high fever (90%), atypical lymphocytes (67%), mild mucosal involvement (56%) and lymphadenopathy (54%). The reaction was protracted in all but two patients; two patients died during the acute phase. Drug causality was plausible in 88% of cases. Antiepileptic drugs were involved in 35%, allopurinol in 18%, antimicrobial sulfonamides and dapsone in 12% and other antibiotics in 11%. The median time interval after drug intake was 22 days (interquartile range 17-31) for all drugs with (very) probable causality, with differences between drugs.

CONCLUSION

This prospective observational study supports the hypothesis that DRESS is an original phenotype among SCAR in terms of clinical and biological characteristics, causative drugs, and time relation. The diversity of causative drugs was rather limited, and mortality was lower than that suggested by prior publications.

The role of prior corticosteroid use on the clinical course of Stevens-Johnson syndrome and toxic epidermal necrolysis: a case-control analysis of patients selected from the multinational EuroSCAR and RegiSCAR studies

BACKGROUND

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are immunologically mediated, severe cutaneous adverse reactions involving cytotoxic T cells, natural killer cells and various mediators. In large studies, up to 15% of SJS/TEN occurred in patients with chronic corticosteroid use. It is unclear if this prior exposure to corticosteroids modified the disease course.

OBJECTIVES

To evaluate whether systemic corticosteroid usage prior to the onset of SJS/TEN modified the clinical course and outcome. If a disease-modifying effect is present, information from such an analysis may have implications on the therapeutic use of corticosteroids in SJS/TEN.

METHODS

This is a case-control study based on data collected in the EuroSCAR and RegiSCAR studies. Ninety-two cases of SJS/TEN with exposure to corticosteroids prior to the onset of disease, and 321 randomly selected SJS/TEN patients without prior exposure were included. Primary outcomes included progression of disease, disease severity and mortality. A secondary analysis of latency between the beginning of drug use and the onset of disease, based on exposure to a single high-risk drug, was also performed.

RESULTS

On multivariate analysis, cases with prior exposure to corticosteroids had a longer progression of disease by 2·2 days [95% confidence interval (CI) 1·1-3·2]. The disease severity and mortality outcome were unaffected. In addition, there is evidence that corticosteroids delayed the onset of SJS/TEN in patients with exposure to high-risk drugs by 7·1 days (CI -0·2 to 14·5).

CONCLUSIONS

The prior use of corticosteroids prolonged the period of disease progression without influencing the disease severity or mortality. In addition, when SJS/TEN is preceded by use of a single high-risk drug, the latency between the drug intake and the onset of SJS/TEN may also be increased. These findings suggest that corticosteroids have a mild impact on the course of SJS/TEN, and further studies are required to clarify any potential therapeutic effects.

Stevens-Johnson syndrome and toxic epidermal necrolysis in patients with lupus erythematosus: a descriptive study of 17 cases from a national registry and review of the literature

BACKGROUND

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe cutaneous adverse reactions with high morbidity and mortality. Some expressions of lupus erythematosus (LE) may cause enormous difficulties in differentiating them from SJS and TEN by showing large areas of sheet-like epidermal necrosis.

OBJECTIVE

To evaluate clinically and histopathologically probable or definite cases of SJS/TEN with a history of systemic or other LE [(S)LE].

METHODS

This was a retrospective analysis of validated cases of SJS/TEN with a history of (S)LE, based on a large population-based national registry.

RESULTS

Among 1366 patients with SJS/TEN, 17 with a sufficiently documented history of (S)LE and representative histological material could be identified, suggesting a considerable over-representation of LE in patients with SJS/TEN. Eight of these showed clinically and/or histopathologically some LE-characteristic features interfering with the diagnosis of SJS/TEN. Differentiation could be elaborated on clinical and histopathological grounds: four patients were classified as SJS/TEN with a preceding (S)LE exacerbation and/or LE-typical histopathological features, and four as 'TEN-like' (S)LE.

CONCLUSION

Most patients with SJS/TEN and a history of (S)LE demonstrate clinical and histopathological properties allowing clear differentiation. However, occasionally acute cutaneous manifestations of (S)LE and SJS/TEN can be phenotypically similar, caused by extensive epidermal necrosis. Although no feature by itself is conclusive, a combination of recent (S)LE exacerbation, evident photodistribution, annular lesions and absent or only mild focal erosive mucosal involvement may favour LE over SJS/TEN clinically. Histopathologically, in particular, junctional vacuolar alteration, and the presence of solitary necrotic keratinocytes at lower epidermal levels, combined with moderate to dense periadnexal and perivascular lymphocytic infiltrates with a variable presence of melanophages, and mucin point to a LE-related origin.

Poor relevance of a lymphocyte proliferation assay in lamotrigine-induced Stevens-Johnson syndrome or toxic epidermal necrolysis

BACKGROUND

Prior use of 'lymphocyte transformation test' (LTT) in Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) provided conflicting results, possibly dependent on sampling dates (acute vs. late).

OBJECTIVE

Evaluation of LTT in patients with SJS or TEN who reacted to lamotrigine (LTG). In a small subgroup we explored the possible role of regulatory T cells (T-reg).

METHODS

Acute phase samples (9) and post-recovery samples (14) from cases of SJS or TEN to LTG were provided by the RegiSCAR-study group. Controls were persons never exposed to LTG (12), patients exposed without reaction (6), and patients who developed a mild eruption to LTG (6). LTT was performed by measuring (3) H-thymidine incorporation after 3 days of incubation with phytohemmaglutinin, LTG (10 μg/mL) or medium. Stimulation index ≥ 2 was considered positive. In 16 cases LTT was redone after depletion of T-reg by fluorescence activated cell sorting.

RESULTS

Positive LTT was observed in 3/6 cases of mild eruptions, 1/9 SJS/TEN-cases tested during the acute phase and 3/14 SJS/TEN-cases tested after recovery. We noted a very mild and nonsignificant trend for an increased response after depletion of T-reg in late samples from SJS or TEN patients.

CONCLUSIONS AND CLINICAL RELEVANCE

With the largest number of LTT performed in patients with SJS or TEN to a single drug, we confirmed that reactive cells are rarely detected in these reactions. Poor reactivity did not seem related to T-reg. Other in vitro assays than those testing proliferation should be evaluated, before raising the hypothesis that specific cells disappeared by undergoing apoptosis during the reaction.

An application of propensity score methods to estimate the treatment effect of corticosteroids in patients with severe cutaneous adverse reactions

PURPOSE

To investigate whether propensity score (ps) methods could reasonably be applied to estimate the treatment effect on mortality, based on a comparatively small sample of patients with severe cutaneous adverse reactions (SCAR) and who come from different countries where physicians prefer different treatment schemes.

METHODS

Ps methods were applied to cope with confounding due to non-randomized treatment assignment for the analysis of the treatment data obtained in the case-control study EuroSCAR. For the study's purpose, the analysis focused on the comparison of the treatments: corticosteroids (STER) and supportive care only (SUPP).

RESULTS

206 French and German patients were treated either with SUPP or STER. Imbalances between treatment groups as well as between the countries were recognized. Concerning the balance between the treatment groups no ps model for the full cohort was satisfying. In addition, the inclusion of a variable for patient's country led to a separation of the patients by country. Thus, we developed ps models for each country separately and estimated the treatment effects (France: odds ratio (OR) 0.52, 95% confidence interval (CI) 0.09-3.10, Germany: OR 0.23, CI 0.06-0.92, Overall: OR 0.33 CI 0.11-1.04).

CONCLUSIONS

The application of the ps methods was successful and provided valuable information. We could confirm the findings of the original analysis which was based on standard logistic regression, especially concerning the necessity of a country-specific analysis. The observed country differences in the estimated treatment effects were less pronounced and thus seemed to be more reasonable than those of the past analysis.

Risk factors for acute generalized exanthematous pustulosis (AGEP)-results of a multinational case-control study (EuroSCAR)

BACKGROUND

Acute generalized exanthematous pustulosis (AGEP) is a disease characterized by the rapid occurrence of many sterile, nonfollicular pustules usually arising on an oedematous erythema often accompanied by leucocytosis and fever. It is usually attributed to drugs.

OBJECTIVES

To evaluate the risk for different drugs of causing AGEP.

PATIENTS AND METHODS

A multinational case-control study (EuroSCAR) conducted to evaluate the risk for different drugs of causing severe cutaneous adverse reactions; the study included 97 validated community cases of AGEP and 1009 controls. Results Strongly associated drugs, i.e. drugs with a lower bound of the 95% confidence interval (CI) of the odds ratio (OR) > 5 were pristinamycin (CI 26-infinity), ampicillin/amoxicillin (CI 10-infinity), quinolones (CI 8.5-infinity), (hydroxy)chloroquine (CI 8-infinity), anti-infective sulphonamides (CI 7.1-infinity), terbinafine (CI 7.1-infinity) and diltiazem (CI 5.0-infinity). No significant risk was found for infections and a personal or family history of psoriasis (CI 0.7-2.2).

CONCLUSIONS

Medications associated with AGEP differ from those associated with Stevens-Johnson syndrome or toxic epidermal necrolysis. Different timing patterns from drug intake to reaction onset were observed for different drugs. Infections, although possible triggers, played no prominent role in causing AGEP and there was no evidence that AGEP is a variant of pustular psoriasis.

A marker for Stevens-Johnson syndrome …: ethnicity matters

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are rare but severe cutaneous adverse drug reactions, which can be caused by a certain number of specific drugs among which is carbamazepine, an antiepileptic agent. A very strong association of carbamazepine-induced SJS with HLA-B*1502 has recently been described in the Han Chinese population. Here in, we report preliminary results from a European study (RegiSCAR) of 12 carbamazepine-induced SJS/TEN cases (nine French and three German). Among these only four had a HLA-B*1502 allele. Remarkably, these four patients had an Asian ancestry, whereas the others did not as far as we have ascertained. This shows that although the HLA region may contain important genes for SJS, the HLA-B*1502 allele is not a universal marker for this disease and that ethnicity matters.

Schwere Arzneimittelreaktionen der Haut

Toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) are severe drug-induced bullous skin reactions. They are rare, but often life-threatening and have a high mortality rate. Acute generalized exanthematous pustulosis (AGEP) is a severe cutaneous adverse reaction, but after the suspected drug is withdrawn, the skin heals rapidly and mortality is low. The clinical pattern, histology and inducing drugs differ substantially between AGEP and the SJS/TEN group.

Interventions for toxic epidermal necrolysis

BACKGROUND

Toxic epidermal necrolysis is a rare condition where a drug reaction induces skin loss, similar to that seen in extensive burns. It is associated with high morbidity and mortality and there is no clear agreement on effective treatment.

OBJECTIVES

To assess the effects of all interventions for the treatment of toxic epidermal necrolysis.

SEARCH STRATEGY

We searched the Cochrane Skin Group Specialised Register (March 2001), the Cochrane Controlled Trials Register (March 2001), MEDLINE (1966 to December 2001), EMBASE (1980 to December 2001), DARE (4th Quarter 2001) and CINAHL (1982 to October 2001).

SELECTION CRITERIA

Randomised controlled trials of therapeutic and supportive interventions that included participants clinically diagnosed with toxic epidermal necrolysis were included.

DATA COLLECTION AND ANALYSIS

Two independent reviewers carried out study selection and assessment of methodological quality.

MAIN RESULTS

Only one randomised controlled trial of treatment was identified. This trial compared the effectiveness of thalidomide with placebo and included 22 patients, 12 in the treatment group and 10 in the placebo group. Patients on the treatment arm received thalidomide 200 mg twice daily for 5 days. The main end point was the measurement of the progression of skin detachment after 7 days. Other end points were the overall mortality and severity of the disease evaluated with the simplified acute physiology score. The study was terminated as the mortality on the treatment arm was 83% compared to 30% on the control arm (relative risk 2.78, 95% confidence interval 1.04 to 7.40). No randomised controlled trials of the most commonly used current treatments i.e. systemic steroids, cyclosporin A and intravenous immunoglobulins were found.

REVIEWER'S CONCLUSIONS

Treatment with thalidomide was not shown to be effective and was associated with significantly higher mortality than placebo. There is no reliable evidence on which to base treatment for toxic epidermal necrolysis, a disease commonly associated with mortality rates of around 30%. More research is required to understand the mechanisms of toxic epidermal necrolysis. International multi-centre studies are needed in the form of randomised controlled trials, to evaluate treatments for toxic epidermal necrolysis, especially those using high doses of steroid and intravenous immunoglobulins.

[Reproducible drug exanthema to terbinafine with characteristic distribution of baboon syndrome]

A 26 year old patient developed a fixed drug eruption located on his hands, inguinal and gluteal areas following oral treatment of onychomycosis with terbinafine. The rash showed the characteristic distribution of the "baboon-syndrome", so-named because of the red perianal region of the baboon. Although epicutaneous testing revealed no positive reaction, the rash could be induced in identical sites by oral administration of terbinafine. As the underlying pathomechanism for the "baboon-syndrome" a systemically induced allergic contact dermatitis has been suggested. In addition to the described substances, e.g. mercury, amoxicillin, ampicillin, heparin and nickel, this is the first report of "baboon syndrome" induced by terbinafine.

Nevirapine and the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis

OBJECTIVE

To draw attention to the many cases of Stevens-Johnson syndrome (SJS) or toxic epidermal necrolysis (TEN) related to nevirapine detected in a multinational case-control study of SJS and TEN.

METHODS

Actively detected cases and matched hospital controls were interviewed for exposure to drugs and other risk factors. Data were analysed with case-control and case-crossover methods.

RESULTS

Between May 1997 and November 1999, a diagnosis of SJS or TEN was established in 246 patients. Eighteen were known to be infected by HIV-1 (7.3%), 15 out of these 18 had been exposed to nevirapine. The reaction began 10-240 days after the introduction of nevirapine (median, 12 days) and all patients had received escalating doses. In 10 patients the reaction occurred with the initial dosage. All but one patients received simultaneously a variety of other antiretroviral agents but no specific drug combination emerged, and nevirapine was the only drug significantly associated with an increased risk of SJS or TEN in HIV-infected persons [odds ratio, 62 (10.4; +infinity) in the case-control analysis; odds ratio, +infinity (2.8; +infinity) in the case-crossover analysis].

CONCLUSIONS

In European countries the risk of SJS or TEN in the context of HIV infection appears to be associated with nevirapine. The respect of a lead-in period does not appear to prevent SJS or TEN. Because of the severity of these reactions and the long elimination half-life of nevirapine, we suggest discontinuation of the drug as soon as any eruption occurs.

[Linear IgA dermatosis in an adult with clinical signs of Stevens-Johnson syndrome]

Immunohistologically linear IgA disease presents with unambiguous features, whereas clinical manifestations are variable. It sometimes shows similarity to other bullous dermatoses such as bullous pemphigoid and dermatitis herpetiformis. A 73 year old female patient was referred with the diagnosis of bullous pemphigoid. One day after admission clinical examination revealed the classical features of Stevens-Johnson syndrome (SJS): widespread confluent atypical target lesions, partly raised, partly flat with central blisters, and erythematous spots, but few typical targets, as well as blisters and large areas of skin detachment on her back and buttocks, accompanied by erosions of the oral and genital mucosa. Direct immunofluorescence performed on peri-lesional skin showed linear deposition of IgA along the basement membrane zone, leading to the diagnosis of linear IgA disease of adults. Our case report shows that linear IgA disease may present with the clinical pattern of SJS.

The dermal type of erythema multiforme: a rare variant of Stevens-Johnson syndrome or cases of clinical misclassification?

Since 01.04.90 the Dokumentationszentrum schwerer Hautreaktionen (dZh) in Freiburg has registered cases of severe skin reactions like erythema exsudativum multiforme majus, Stevens-Johnson syndrome and toxic epidermal necrolysis in Germany. With the largest study so far of histological slides from patients included in this registry we were able to show that the epidermal type of erythema multiforme described by Orfanos et al. is the histopathological correlated of these severe skin reactions. Except two biopsies all of the specimens taken from the registered patients showed histological characteristics of this type of erythema multiforme. These two cases are now reported. Clinical data and photographic documentation did not prove authentic erythema multiforme. The lesions of both patients were described as atypical macules and papules; mucosal sites were only locally involved. Biopsies taken from the patients had the characteristics of the dermal type of erythema multiforme (Orfanos et al.). We conclude that histomorphological characteristics of the dermal type, in addition to an atypical clinical course, favour another diagnosis, such as multiforme-like eruption.

Epidemiology of drug-induced severe skin reactions

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe, sometimes life-threatening skin reactions that are often drug-induced. Unfortunately, the definitions and nomenclature of these severe skin reactions have been confusing, and thus various publications on this issue can hardly be compared. After several attempts have been made to clarify this situation, a consensus definition published in 1993 suggests the differentiation between erythema exsudativum multiforme majus (EEMM) and SJS, as well as an overlap group of SJS and TEN, whereas TEN with maculae is the most severe type of skin reaction with more than 30% of skin detachment related to the body surface area (BSA). This classification was applied to cases of severe skin reactions in several large studies that have been undertaken within the last few years and published recently. The incidence of SJS, SJS/TEN overlap and TEN has been estimated to be approximately 1.89 cases per one million people per year. Although SJS and TEN occur very rarely, a mortality rate of more than 40% can be calculated for patients suffering from TEN. One may conclude that mortality increases with age and the amount of skin detachment related to the BSA. A number of drugs have been reported to induce severe skin reactions, eg, anti-infective sulfonamides, antibiotics, anticonvulsants and nonsteroidal anti-inflammatory drugs. For risk evaluation for certain drugs or drug groups population-based data as ascertained by the German registry of severe skin reactions, and prescription data in defined daily doses can be used. In addition, risk evaluation is possible by performing a case-control study as it has been undertaken within different European countries. As long as the pathogenesis of drug-induced severe skin reactions is not known, and specific screening methods to identify susceptible individuals do not exist, the epidemiological approach will remain the only possibility for risk estimation.

Histopathological and epidemiological characteristics of patients with erythema exudativum multiforme major, Stevens-Johnson syndrome and toxic epidermal necrolysis

The clinical and histopathological classification of erythema exudativum multiforme major (EEMM), Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are difficult, due to the lack of clear-cut criteria. Based on a new clinical classification, 149 of 219 (68%) histopathological specimens, from a total of 534 patients with EEMM, SJS and TEN, have been reviewed. A comparison was made with the clinical picture, and any past history of infection or drug intake. All patients had been included in the German Registry of Severe Skin Reactions between April 1990 and December 1993. No differences could be found between the biopsies examined and the total number of histopathological specimens, concerning clinical diagnosis, gender and age. Sections from 28 of 149 specimens were not diagnostic or were too old to be properly evaluated. In nine cases, other diagnoses were proposed. One hundred and eleven of the histological slides with the diagnosis of EEMM (n = 16), SJS (n = 34) and TEN (n = 61), were classified as epidermal type of erythema multiforme. In these 111 slides, necrotic keratinocytes could be found, ranging from individual cells to confluent epidermal necrosis. The epidermo-dermal junction showed changes ranging from vacuolar alteration up to subepidermal blisters. The dermal infiltrate was superficial and mostly perivascular. It was sparse in SJS and TEN, and more pronounced in EEMM. Oedema in the papillary dermis was evident occasionally in all clinical groups. In 59 of 111 cases (53%), at least one eosinophil was present in the dermis. In 11 of 111 (10%), more than 10 eosinophils per field could be seen. Eosinophils were less common in the patients with the most severe forms of TEN, in whom there was detachment of more than 30% of the skin surface area. No differences in the history for drug intake, or for infection with Mycoplasma pneumoniae, herpes simplex and other organisms, could be detected between patients with or without eosinophils in their skin sections. This dermatopathological study of patients with EEMM, SJS and TEN indicates that the epidermal type of erythema multiforme is the pathological correlate for these diseases.

Epidemiology of erythema exsudativum multiforme majus, Stevens-Johnson syndrome, and toxic epidermal necrolysis in Germany (1990-1992): structure and results of a population-based registry

The severe skin reactions erythema exsudativum multiforme majus (EEM with mucosal involvement, EEMM), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) are difficult to study as they are very rare diseases with an incidence of about two cases per 1 million inhabitants per year. We report on the structure of a registry with the aim of ascertaining all hospitalized cases of EEMM, SJS, and TEN in western Germany and Berlin. The registry is structured as an intensive reporting system, regularly contacting more than 1500 departments including 100% of the burn units (n = 34), departments of pediatrics (n = 241), departments of dermatology (n = 106), and 100% of all internal medicine departments in hospitals with intensive care facilities or with more than 200 beds (n = 1161). With a coverage rate up to 95% based on the number of responding departments between April 1, 1990 and December 31, 1992, from a total of 767 reported cases 353 patients with EEMM, SJS, and TEN were finally included in the registry. Most of these patients were directly reported to the registry; only 2.54% (9 of 353) were primarily registered by the German spontaneous reporting systems. Assuming an average population of 64.5 million for western Germany and Berlin an incidence up to 1.89 per 1 million inhabitants per year could be calculated for SJS and TEN.

Low N-acetylating capacity in patients with Stevens-Johnson syndrome and toxic epidermal necrolysis

Low constitutive N-acetylating capacity has been implicated as a predisposing factor for the development of adverse reactions to certain drugs. This prompted us to investigate whether the N-acetylating capacity of patients with serious cutaneous adverse reactions, i.e., Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) differed from that of healthy control subjects. N-acetylating activity was measured in hair root cells by preparing a homogenate from freshly extracted hair roots and assessing acetyl-CoA-dependent N-acetylation by RP-HPLC using 2-aminofluorene as a substrate. Samples were obtained from hospitalized patients suffering from acute SJS and TEN or from healthy controls. All patients with SJS and TEN were found to have a low N-acetylating capacity (0.85 nmol/mg/min compared to 2.21 nmol/mg/min in controls, p < 0.05). Based on these findings, a low constitutive N-acetylating capacity may be one of the predisposing factors for the development of serious cutaneous adverse reactions to drugs that require N-acetylation in these patients.