A patient on co-trimoxazole for urinary tract infection develops target lesions with three distinct zones (central dark area, pale edematous ring, outer erythematous halo) over palms, soles, and oral mucosa. There is no skin detachment. What is the diagnosis?

• A Stevens-Johnson syndrome
• B Erythema multiforme major ✓
• C Toxic epidermal necrolysis
• D Fixed drug eruption

Explanation

Erythema multiforme major presents with classic three-zone target lesions (iris lesions) predominantly on palms and soles with mucosal involvement of two or more sites, but the epidermal detachment is absent or minimal (<10% BSA). The target lesion's three zones correspond to central necrosis (dark), perilesional edema (pale ring), and peripheral erythema. Stevens-Johnson syndrome also has mucosal involvement and epidermal detachment >10% but <30% BSA. Common triggers include HSV infection and drugs like sulfonamides and anticonvulsants.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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