SJS/TEN — SCE Dermatology MCQ

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ModerateDrug ReactionsSJS/TENSCE Dermatology

A 48-year-old woman with no significant past medical history presents with sudden onset of widespread painful skin tenderness followed by large sheets of epidermis sloughing with gentle lateral pressure. She was started on Allopurinol 3 weeks ago. BSA of epidermal detachment is 35%. What is the diagnosis?

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Correct answer: D — Toxic epidermal necrolysis

The correct answer is D, toxic epidermal necrolysis (TEN). The UK guidelines for SJS/TEN define severity by percentage of body surface area (BSA) of epidermal detachment: SJS affects less than 10 percent, SJS/TEN overlap 10 to 30 percent, and TEN more than 30 percent. This patient has 35 percent BSA detachment with a positive Nikolsky sign (sheet-like sloughing on gentle lateral pressure), fulfilling the diagnostic threshold for TEN rather than the overlap or SJS categories. Allopurinol is one of the classic high-risk culprit drugs for TEN, typically triggering the reaction within the first few weeks of exposure, consistent with the three-week timeline here. The combination of a known high-risk drug, prodromal skin pain, and detachment exceeding 30 percent BSA is diagnostic of TEN and mandates urgent burns unit or ICU-level care.

Reference: https://www.nice.org.uk/guidance/conditions-and-diseases/skin-conditions