(A) Peripheral blood shows neutrophils with toxic granules and two intra-cytoplasmic yeast forms of Histoplasma capsulatum in the cell on the left (May-Grunwald Giemsa, ×1,000). Inset: The fungus was brightly positive for periodic acid–Schiff stain (hematoxylin counterstain, ×1,000). (B) Hemodilute bone marrow smears showed dysgranulopoiesis with 5% blasts (May-Grunwald Giemsa, ×1,000). Inset: Ring sideroblasts comprised 32% of all cells (Perls' Prussian Blue reaction with neutral red counterstain, ×1,000). (C) Bone marrow biopsy showed intracellular yeast forms (hematoxylin and eosin, ×400). Inset: These were positive for Grocott's silver methenamine stain (methyl green counterstain, ×1,000). (D) Lactophenol cotton blue wet-mount preparation of the isolated mold shows thick-walled and tuberculate macroconidia, with a close-up in the inset (lactophenol cotton blue stain, ×1,000).