Histoplasma capsulatum in peripheral blood neutrophils

Excerpt

A 45-year-old female presented with chief complaints of moderate- to high-grade fever for 4 months associated with drenching night sweats. Physical examination revealed hepatosplenomegaly, 10 and 12 cm below costal margins, respectively. Her complete blood count showed anemia (78 g/L), thrombocytopenia (20 × 10⁹/L), and total leukocyte count (4.6 × 10⁹/L). The differential leukocyte count (DLC) at presentation was as follows: neutrophils 80%, lymphocytes 13%, eosinophils 04%, monocytes 01%, myelocytes 01%, and metamyelocytes 01%. The patient had a history of seronegative rheumatoid arthritis and was taking methotrexate or azathioprine intermittently. A peripheral blood smear obtained on admission showed a few neutrophils with one to multiple, small, intracellular yeast-like organisms with crescent-like eccentric chromatin. The organisms were ovoid in shape and surrounded by a cytoplasmic halo (Fig. 1a; original magnification × 1000, Leishman stain). Periodic acid–Schiff (PAS) stain highlighted the rim of these organisms. These features are consistent with diagnosis of Histoplasma capsulatum var. capsulatum. Subsequent bone marrow aspiration and biopsy were performed which revealed numerous histiocytes filled with H. capsulatum yeast forms. Some of the histiocytes show hemophagocytosis (Fig. 1b and c; original magnification × 1000, May-Grünwald Giemsa and Gomori-methenamine silver stain). The patient was treated with amphotericin B and showed remarkable clinical improvement.

…