Bone marrow nonneoplastic
Infectious / inflammatory
Histoplasmosis
Author: Dragos C. Luca, M.D.
Last author update: 1 August 2014
Last staff update: 29 January 2021
Copyright: 2002-2019, PathologyOutlines.com, Inc.
PubMed Search: Histoplasmosis bone marrow [title]
Table of Contents
Definition / general | Case reports | Microscopic (histologic) description | Positive stains | Additional referencesCite this page: Luca DC. Histoplasmosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bonemarrowhistoplasmosis.html. Accessed June 3rd, 2023.
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
- 43 year old woman with acquired immunodeficiency syndrome and fever of undetermined origin (Arch Pathol Lab Med 2006;130:120)
- Patient with disseminated histoplasmosis complicating bone marrow transplantation (Am J Clin Pathol 1983;79:509)
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%
Positive stains
