Histoplasma capsulatum in the Peripheral Blood Smear: A Rare Occurrence

A 20 year old male presented with history of pain abdomen, abdominal distention and diarrhea since 3 weeks. On examination, he had massive hepatosplenomegaly. Imaging (CECT, whole abdomen) showed changes suggestive of non-cirrhotic portal hypertension. HIV, HBsAg and HCV testing was negative. Complete haemogram revealed pancytopenia (Haemoglobin: 8.7 g/dL total leucocyte count: 2010/uL and platelet count: 17,000/uL). Peripheral smear revealed presence of small yeast-like organisms, measuring 2–4 microns with amaranth nuclei and capsule-like unstained halos around, in the cytoplasm of monocytes lying in the extreme tail-end. They were positive for Periodic Acid Schiff (PAS) and Gomori Methanamine Silver (GMS) stain (Fig. 1). Bone marrow examination revealed numerous histiocytes loaded with similar organisms with identical staining properties. Features of the organism was consistent with Histoplasma capsulatum (Fig. 2). The culture reports are still awaited. The patient was started on amphotericin B and was investigated for immunodeficiency disorders. The results were non-contributory.

Fig. 1.

Peripheral smear examination revealing presence of intracellular Histoplasma capsulatum in monocyte (a Giemsa 100X,b PAS 100X,c GMS 100X)

Fig. 2.

Bone marrow aspirate smear showing macrophage with Histoplasma capsulatum (a Giemsa 100X,b PAS 100X,c GMS 100X)

Finding Histoplasma capsulatum, a dimorphic fungi in peripheral smear is not common and this case underscores importance of careful examination of peripheral blood smear in routine practice as it may aid in diagnosis of an associated disseminated infection in an immunocompromised host as illustrated by Sharma et al. [1] Kauffman has also reported the presence of Histoplasma species in peripheral blood smear in neutrophils, associated with disseminated infection and poor prognosis [2].

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Conflict of interest

Nil.