Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are distinguished by body surface area of epidermal detachment. What percentage defines TEN?

• A Less than 5% — SJS; greater than 20% — TEN
• B Less than 15% — SJS; greater than 25% — TEN
• C Any mucous membrane involvement — TEN
• D Less than 10% BSA — SJS; 10–30% overlap; greater than 30% — TEN ✓

Explanation

The Bastuji-Garin classification distinguishes: SJS (epidermal detachment <10% BSA), SJS/TEN overlap (10–30%), and TEN (>30%). Both involve mucosal erosions, purpuric macules, and atypical target lesions. The SCORTEN (Severity of Illness Score for TEN) uses 7 variables to predict mortality. The most common causative drugs are allopurinol, carbamazepine (associated with HLA-B*1502 in Asians), lamotrigine, sulfamethoxazole, nevirapine, and oxicam NSAIDs.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.