This blood smear was taken from an immunodeficient man with fever, night sweats, and weight loss. What is the diagnosis?

Answer D. Histoplasma capsulatumThe peripheral-blood smear shows a monocyte with a grossly distorted nucleus and numerous intracellular yeast-like organisms 2 to 4 micrometers in diameter with eccentric chromatin. The organisms were surrounded by an artifactual pseudocapsule caused by cytoplasmic shrinkage. These features are diagnostic of Histoplasma capsulatum. H. capsulatum is acquired by the inhalation of conidia or mycelial fragments.