A 50-Year-Old Man Comes to the Physician Because of a 4-Week

A 50-year-old man comes to the physician because of a 4-week history of intermittent fevers, productive cough, and shortness of breath. Three weeks ago he was treated with amoxicillin-clavulanate and azithromycin, which did not improve his symptoms. He is also worried because he has noticed "some new bumps on his skin". He lives in upstate New York along the Mohawk River. He has rheumatoid arthritis. He does not smoke cigarettes. His medications include methotrexate and a multivitamin. His temperature is 38.1ºC (100.6°F) , pulse is 72/min, respirations are 16/min, and blood pressure is 128/75 mm Hg. Diffuse crackles are heard over both lung fields. Skin examination shows multiple, white, verrucous papules and nodules on the thighs. A CT scan of the chest shows bilateral tree-in-bud opacities in the lower lobes. A biopsy of a skin nodule shows pyogranulomatous inflammation and round yeast cells. Which of the following is the most likely causal pathogen?

A) Blastomyces dermatitidis
B) Candida albicans
C) Mucor species
D) Penicillium marneffei
E) Pneumocystis jiroveci