Cutaneous anthrax — DTM&H MCQ

Correct answer: E — Cutaneous anthrax

Cutaneous anthrax (E) is correct because a painless papule progressing to a black necrotic eschar with marked non-pitting oedema, following occupational exposure to animal hides in an abattoir worker, is the classic and pathognomonic presentation of Bacillus anthracis skin infection. Cattle and their hides are a recognised reservoir, with spores entering through minor skin breaks on exposed sites such as the hands. The initial lesion typically evolves from an erythematous papule with a rim of small bullae into a painless ulcer that develops a central black eschar surrounded by striking oedema, exactly as described in the stem. Painlessness despite the dramatic local appearance is the key discriminating clinical feature that separates anthrax from most other infective skin lesions, and the occupational hide-handling history in an endemic area (South Asia) strongly supports the diagnosis. Why the other options are wrong: C. Cutaneous leishmaniasis: presents as a chronic, slowly enlarging painless nodule or ulcer with a raised, indurated border, transmitted by sandfly bites, not linked to hide handling and lacking the black eschar with surrounding oedema described here. D. Tularaemia: causes a painful ulcer with tender regional lymphadenopathy following contact with infected animals (classically rabbits or ticks), and the ulcer is not typically a black eschar with prominent surrounding oedema. B. Orf: a parapoxvirus infection from sheep or goats causing a painful or itchy vesiculo-pustular nodule that evolves through papillomatous and crusted stages, self-limiting, without the necrotic black eschar or hide-exposure link. A. Mycobacterium marinum infection: follows exposure to fish tanks or aquatic environments, producing slowly progressive nodules or verrucous plaques along lymphatics, not an acute painless eschar after hide contact. Key point: a painless black eschar with surrounding oedema in someone handling hides, wool or animal products is cutaneous anthrax until proven otherwise.

Reference: Primary Care Dermatology Society (PCDS), Clinical Guidance: Anthrax, https://www.pcds.org.uk/clinical-guidance/anthrax