SJS/TEN — SCE Dermatology MCQ

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HardDrug ReactionsSJS/TENSCE Dermatology

A 35-year-old man develops a widespread erythematous rash with target-like lesions after starting Phenytoin. Unlike true erythema multiforme targets, these lesions have only two zones (dusky centre and erythematous rim) without the classic three-zone morphology. What are these called?

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Correct answer: A — Atypical targets (consistent with drug-induced SJS spectrum rather than EM)

The distinction between typical (three-zone) and atypical (two-zone) target lesions is clinically important. Typical targets (three zones: dusky centre, oedematous pale ring, erythematous outer ring) are characteristic of erythema multiforme, most commonly triggered by HSV. Atypical targets (two zones only: dusky centre and erythematous rim, often with central blister) are more characteristic of the SJS/TEN spectrum, typically drug-induced. Phenytoin is a well-known cause of SJS/TEN (particularly in HLA-B*1502-positive individuals of Southeast Asian ancestry). This morphological distinction helps differentiate EM (usually benign, HSV-associated) from SJS (potentially life-threatening, drug-associated).

Reference: BAD 2016 SJS/TEN Guidelines; Bastuji-Garin Classification