Chromoblastomycosis — DTM&H MCQ

Correct answer: C — Chromoblastomycosis

The correct answer is C, chromoblastomycosis. This chronic subcutaneous mycosis is caused by dematiaceous (pigmented) fungi such as Fonsecaea pedrosoi and Cladophialophora carrionii, which are inoculated through minor skin trauma (often barefoot agricultural work) in tropical and subtropical regions including sub-Saharan Africa. It classically produces slowly progressive verrucous, cauliflower-like plaques on the lower limbs over years, with occasional satellite lesions from autoinoculation. The pathognomonic histological finding is the muriform (sclerotic, copper-penny) cell: a thick-walled, brown, septate fungal cell dividing by internal septation rather than budding, seen within dermal granulomas. This combination of chronic verrucous morphology plus muriform cells on histology is diagnostic and distinguishes it from other tropical fungal and mycobacterial infections, guiding treatment with prolonged itraconazole, often combined with terbinafine or physical modalities such as cryotherapy or local heat therapy. Why the other options are wrong: B. Eumycetoma: presents with painless subcutaneous swelling, sinus tracts and discharge containing fungal grains, not verrucous plaques, and histology shows grains, not muriform cells. E. Sporotrichosis: typically causes nodular lymphangitis with ascending subcutaneous nodules along lymphatics after inoculation, and histology shows cigar-shaped yeasts, not muriform cells. D. Cutaneous leishmaniasis: produces painless ulcers with raised indurated borders that usually heal within months, and biopsy shows amastigotes within macrophages, not fungal elements. A. Verrucous tuberculosis: (tuberculosis verrucosa cutis) shows warty hyperkeratotic plaques but histology reveals caseating granulomas with acid-fast bacilli, never muriform fungal cells. Key point: Verrucous, slowly progressive skin lesions with copper-penny (muriform) cells on histology are diagnostic of chromoblastomycosis and mandate prolonged itraconazole-based antifungal therapy.

Reference: BNF (NICE), Itraconazole: Indications and dose, systemic fungal infection, https://bnf.nice.org.uk/drugs/itraconazole/