The spectrum of Stevens-Johnson syndrome and toxic epidermal necrolysis: a clinical classification.

The nosology of severe bullous erythema multiforme (EM), Stevens-Johnson syndrome (SJS), and toxic epidermal necrolysis (TEN) remains controversial. To conduct a prospective case-control study of the etiologic factors of these diseases, we needed to define criteria for classifying the cases. After having reviewed photographs of the skin lesions of more than 200 patients, an international group of dermatologists proposed a classification based on the pattern of "EM-like lesions" (categorized as typical targets, raised or flat atypical targets, and purpuric macules) and on the extent of epidermal detachment. The "consensus" classification in five categories was as follows: bullous erythema multiforme, detachment below 10% of the body surface area (BSA) plus localized typical targets or raised atypical targets; SJS, detachment below 10% of the BSA plus widespread erythematous or purpuric macules or flat atypical targets; overlap SJSTEN, detachment between 10% and 30% of the BSA plus widespread purpuric macules or flat atypical targets; TEN with spots, detachment above 30% of the BSA plus wide-spread purpuric macules or flat atypical targets; TEN without spots, detachment above 10% of the BSA with large epidermal sheets and without any purpuric macules or target. Whether all five categories proposed represent distinct etiopathologic entities will require further epidemiologic and laboratory investigations.