A 70-year-old man has diffuse malaise, oral pain, and a widespread tender erythroderma that began after starting trimethoprim-sulfamethoxazole five days ago for a skin infection. An exam shows signs of a mucocutaneous eruption. Which classic finding on physical examination is most likely associated with the underlying diagnosis?

• A. Desquamation of the skin with minor friction
• B. Targetoid lesions on palms
• C. Painless mucosal ulcers
• D. Papular rash with annular lesions

Answer: (A)

This item is testing recognition of Stevens-Johnson syndrome/toxic epidermal necrolysis as a severe drug reaction. A hallmark feature on exam is a positive Nikolsky sign: the skin peels or desquamates with gentle friction or lateral pressure due to widespread epidermal necrosis from the drug-triggered reaction. The patient’s recent use of trimethoprim-sulfamethoxazole and the mucocutaneous eruption fit this pattern, with painful mucosal involvement and widespread tenderness.

Other options describe different patterns (for example, targetoid lesions on the palms suggest erythema multiforme, which is usually milder; painless mucosal ulcers are not typical of SJS; a papular rash with annular lesions doesn’t capture the extensive epidermal detachment seen in SJS/TEN). The desquamation with minor friction best matches the underlying process and clinical sign of this severe drug reaction.