Histoplasma capsulatum in peripheral blood smears

A 39-year-old man with acquired immunodeficiency syndrome (AIDS; CD4 count 10 x 10 12 / 1) presented with weight loss, fevers and pancytopenia, with Hb 7·1 g / dl, platelet count 72 x 10 9 x l and white cell count 1·8 x 10 9 / l. A peripheral blood film revealed occasional circulating neutrophils containing intracytoplasmic oval, yeast-like organisms approximately 3 μm in length (top). Large numbers of yeast cells were present in association with mononuclear cells on buffy coat preparation (bottom), and within histiocytes and fat lobules on subsequent bone marrow trephine biopsy. Microbiological cultures of the bone marrow sample grew Histoplasma capsulatum variant capsulatum. With the institution of amphotericin B, fevers resolved and the peripheral blood count slowly recovered over the subsequent 6 weeks