Chromoblastomycosis — DTM&H MCQ

Correct answer: B — Chromoblastomycosis

The correct answer is B, Chromoblastomycosis. This is a chronic subcutaneous fungal infection caused by dematiaceous (pigmented) fungi such as Fonsecaea pedrosoi, typically inoculated through minor trauma from thorns or splinters in tropical agricultural workers, exactly as described in this Madagascan farmer with a remote thorn injury. Over years, lesions evolve into slowly progressive verrucous plaques, classically on the lower leg. The diagnostic histological hallmark is the presence of brown, thick walled, muriform (sclerotic or Medlar) bodies, which are pathognomonic and confirm the diagnosis. No other option in this list produces this specific fungal histology, making the biopsy finding the key discriminator. Why the other options are wrong: C. Sporotrichosis: caused by Sporothrix schenckii, also follows traumatic inoculation but typically produces nodular lymphangitis with ascending subcutaneous nodules along lymphatics, and histology shows cigar shaped yeasts, not sclerotic bodies. D. Buruli ulcer: caused by Mycobacterium ulcerans, presents with painless nodules progressing to large undermined necrotic ulcers with a necrotic slough, not verrucous plaques, and histology shows extensive coagulative necrosis with extracellular acid fast bacilli. E. Post-kala-azar dermal leishmaniasis: occurs after visceral leishmaniasis treatment, mainly in East Africa and the Indian subcontinent, causing macular, papular or nodular facial and truncal lesions; biopsy shows amastigotes, not sclerotic bodies, and it is not linked to thorn injury. A. Leprosy reversal reaction: an immunological reaction in existing leprosy causing acute inflammation and tenderness of established skin lesions and nerves, not a slowly progressive verrucous plaque, and biopsy shows granulomatous inflammation with mycobacteria or their remnants, not fungal elements. Key point: Brown sclerotic (Medlar) bodies on biopsy following traumatic implantation are pathognomonic for chromoblastomycosis.

Reference: MSD Manual Professional Edition (Merck), Chromoblastomycosis: diagnosis confirmed by observation of muriform (sclerotic/Medlar) bodies in tissue, pathognomonic of disease, https://www.msdmanuals.com/professional/infectious-diseases/fungal-infections/chromoblastomycosis