A 35-year-old farmer from rural Uttar Pradesh presents with verrucous skin lesions and a chronic pulmonary cavity. Sputum culture on Sabouraud dextrose agar at 25°C grows a mold with tuberculate macroconidia. On brain heart infusion agar with blood at 37°C, it converts to yeast forms. Which dimorphic fungus is most likely?
- A Histoplasma capsulatum var. capsulatum ✓
- B Blastomyces dermatitidis
- C Coccidioides immitis
- D Sporothrix schenckii
Correct answer: A. Histoplasma capsulatum var. capsulatum
Explanation
Histoplasma capsulatum var. capsulatum produces distinctive large, thick-walled tuberculate macroconidia on mold-phase culture at 25°A, a classic identifying feature. It is endemic in the Gangetic plains of India (UP, West Bengal). Blastomyces has broad-based budding yeast but smooth or finely puckered macroconidia without tubercles. Coccidioides produces barrel-shaped arthroconidia, not tuberculate macroconidia. Sporothrix shows delicate hyphae with rosette-like conidia.
Reference: Jawetz, Melnick, and Adelberg's Medical Microbiology, 28th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.