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Dermatology · Cutaneous tuberculosis: papulonecrotic tuberculid
Sample itemA young adult with pulmonary tuberculosis has symmetric crops of dusky papules with central necrosis on the extensors of the limbs, healing with varioloform scars. Biopsy shows a wedge-shaped necrosis with vasculitis. What is the diagnosis?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
A. Papulonecrotic tuberculid
Papulonecrotic tuberculid is a hypersensitivity reaction to tuberculous antigen with leukocytoclastic or granulomatous vasculitis. It heals with scars and clears with antitubercular therapy.
Option by option
A. Papulonecrotic tuberculid (correct)
Correct. Necrotic papules with varioloform scars in a TB patient fit this tuberculid.
B. Secondary syphilis
Secondary syphilis gives palmoplantar macules and positive serology.
C. Pityriasis lichenoides et varioliformis acuta
PLEVA resembles it but has no TB association and shows lymphocytic vasculitis.
D. Lymphomatoid papulosis
Lymphomatoid papulosis shows atypical CD30 positive cells and self-heals.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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