Bone marrow - nonneoplastic
Infectious / inflammatory
Histoplasmosis

Author: Dragos Luca, M.D. (see Authors page)

Revised: 12 July 2017, last major update August 2014

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Histoplasmosis bone marrow [title]

Cite this page: Histoplasmosis. PathologyOutlines.com website. http://pathologyoutlines.com/topic/bonemarrowhistoplasmosis.html. Accessed August 18th, 2017.
Definition / general
  • Fungal infections are rare in the bone marrow and peripheral blood and almost always associated with immunosuppression, including HIV (Pathol Res Pract 2004;200:591)
  • Histoplasma capsulatum: the most common secondary infection in the bone marrow of HIV patients (progressive disseminated histoplasmosis)
  • Infection is common in U.S., particularly in Ohio and Mississippi River valleys
  • Also Central and South America and Caribbean but most infections are subclinical
  • Disseminated disease more common in immunosuppressed, including HIV - may be life threatening in these patients
  • Not always present in bone marrow, even with disseminated infections
Case reports
Microscopic (histologic) description
  • Numerous small, narrow base budding yeast cells (1 - 5 microns) within macrophages
  • Capsule is oval with a colorless circle
  • May also be present within megakaryocytes (Am J Clin Pathol 1991;96:577)
  • Either discrete granulomas, lymphohistiocytic aggregates or diffuse macrophage infiltrates (Am J Clin Pathol 1990;93:367)
  • Granulocytic and erythroid hyperplasia with megakaryocytic hypoplasia
  • May be associated with hemophagocytosis
  • May not elicit granuloma formation in HIV patients but only a diffuse histiocytic proliferation
  • Peripheral blood: intracellular (monocytes, neutrophils) and extracellular yeast forms, anemia; HIV patients have peripheral blood involvement in up to 40 - 50%
Microscopic (histologic) images

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Ill formed granulomas