A 50-year-old farmer from the Midwest presents with fever, cough, and multiple cavitary nodules on chest CT. Biopsy of a lung lesion shows broad-based budding yeast on Grocott methenamine silver stain. Which organism is most likely responsible?
- A Histoplasma capsulatum
- B Coccidioides immitis
- C Blastomyces dermatitidis ✓
- D Cryptococcus neoformans
Correct answer: C. Blastomyces dermatitidis
Explanation
Blastomyces dermatitidis is identified by broad-based budding yeast (the bud has a broad attachment to the parent cell). It is endemic in the Mississippi and Ohio River valleys and the Great Lakes region. Histoplasma (option A) appears as small intracellular yeast within macrophages. Coccidioides (option B) forms large spherules containing endospores, not budding yeast. Cryptococcus (option D) shows narrow-based budding with a mucicarmine-positive capsule.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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