A 50-year-old immunocompromised patient from Maharashtra develops a painless, firm, slow-growing swelling over the ankle with multiple discharging sinuses releasing black grains (melanin-pigmented). Histopathology shows thick-walled brown sclerotic cells (Medlar bodies/muriform cells). The MOST likely diagnosis is:
- A Chromoblastomycosis — caused by dematiaceous fungi such as Fonsecaea pedrosoi or Cladosporium carrionii ✓
- B Mycetoma (Madura foot) with black grains — caused by Madurella mycetomatis (eumycetoma)
- C Phaeohyphomycosis — caused by Alternaria species forming muriform cells in sinuses
- D Sporotrichosis — caused by Sporothrix schenckii with asteroid bodies in tissue
Explanation
Chromoblastomycosis is characterized by the pathognomonic Medlar bodies (sclerotic cells/muriform cells) — thick-walled, dark brown, septate cells that reproduce by equatorial fission. The causative organisms are dematiaceous (melanin-producing) fungi: Fonsecaea pedrosoi (most common globally), Cladosporium carrionii, Phialophora verrucosa, Rhinocladiella aquaspersa. Clinical presentation is slow-growing warty/nodular skin lesions with sinus formation. Mycetoma with black grains (Madurella) shows organized granular structures (grains) in histopathology, not sclerotic cells. Phaeohyphomycosis shows melanin-pigmented hyphae/yeast, not sclerotic cells. Sporotrichosis has cigar-shaped yeast forms with lymphocutaneous spread.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.