A 34-year-old man presents with fever, severe mucosal erosions (eyes, lips, oropharynx), and painful dysuria 14 days after starting carbamazepine for trigeminal neuralgia. Examination reveals atypical targetoid macules on the face and trunk that have rapidly coalesced into dusky, purpuric patches and flaccid bullae. Pressure on involved skin produces full-thickness sloughing in sheets (positive Nikolsky sign) over 22% of body surface area. Skin biopsy demonstrates full-thickness epidermal necrosis with subepidermal cleavage and sparse lymphocytic infiltrate. The clinical and histopathological findings shown in the diagram at **A** are consistent with which classification?

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Accepted Answer

C. SJS-TEN overlap with 10-30% body surface area detachment. ## Why SJS-TEN overlap with 10-30% body surface area detachment is right The patient presents with the classic triad of SJS-TEN: targetoid macules progressing to dusky bullae, mucosal erosions, and a positive Nikolsky sign indicating full-thickness epidermal necrosis with subepidermal cleavage. The 22% body surface area involvement with full-thickness epidermal detachment places this patient squarely in the SJS-TEN overlap category (10-30% BSA), not pure SJS (<10%) or TEN (>30%). Bolognia Dermatology 5e defines this spectrum classification based on the extent of full-thickness epidermal detachment, and the histopathology of full-thickness necrosis with subepidermal cleavage distinguishes this from SSSS. The carbamazepine exposure is a known high-risk drug trigger, particularly in HLA-B*15:02-positive populations. ## Why each distractor is wrong - **Stevens-Johnson Syndrome (SJS) with <10% body surface area detachment**: SJS is defined by <10% BSA involvement. This patient has 22% BSA detachment, which exceeds the SJS threshold and enters the overlap category. - **Toxic Epidermal Necrolysis (TEN) with >30% body surface area detachment**: TEN is defined by >30% BSA involvement. Although this patient has severe disease, the 22% BSA detachment does not meet the threshold for TEN classification. - **Staphylococcal Scalded-Skin Syndrome (SSSS) with intraepidermal cleavage at the granular layer**: SSSS cleaves intraepidermally at the granular layer and lacks full-thickness epidermal necrosis. This patient's biopsy shows full-thickness epidermal necrosis with subepidermal cleavage, a hallmark of SJS-TEN spectrum, not SSSS. **High-Yield:** SJS-TEN overlap is defined by 10-30% full-thickness epidermal detachment; the spectrum is classified by BSA involvement, not clinical severity alone. Full-thickness necrosis with subepidermal cleavage distinguishes SJS-TEN from SSSS (intraepidermal cleavage). [cite: Bolognia Dermatology 5e Ch 20; Bastuji-Garin SCORTEN J Invest Dermatol 2000; Roujeau NEJM 1995]

Answer

A. Toxic Epidermal Necrolysis (TEN) with >30% body surface area detachment

Answer

B. Staphylococcal Scalded-Skin Syndrome (SSSS) with intraepidermal cleavage at the granular layer

Answer

D. Stevens-Johnson Syndrome (SJS) with <10% body surface area detachment

Explanation

Why SJS-TEN overlap with 10-30% body surface area detachment is right

Why each distractor is wrong

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