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Disseminated histoplasmosis diagnosed on bone marrow aspirate cytology: report of four cases
R Pamnani1, J A Rajab, J Githang'a
1Unit of Haematology and Blood Transfusion, Department of Human Pathology, School of Medicine, University of Nairobi, P.O. Box 19676-00202, Nairobi, Kenya.
Abstract:
Histoplasmosis, caused by two varieties of dimorphic fungi, Histoplasma capsulatum variant capsulatum and Histoplasma capsulatum variant duboisii is a systemic fungal infection. It has a worldwide distribution and is shown to be more prevalent in North America and Central America. Both variants occur in Africa. Disease spectrum ranges from asymptomatic primary infection to disseminated disease in immunocompromised patients. Since the upsurge of acquired immune deficiency syndrome (AIDS) and despite the availability of high active anti-retroviral therapy (HAART) many patients still present with opportunistic infections of which histoplasmosis is one. Four cases are presented; two infants and two adults. All had disseminated disease with multiple organ involvement and the disease was not suspected clinically. Diagnosis was made incidentally on bone marrow aspirate cytology. The two adult cases were HIV positive, one with CD4 counts of 132 cells/microlitre and was not on HAART. The other was on HAART but the CD4 had not been determined. One of the infants tested HIV negative and the others status was unknown. A high index of suspicion is required for diagnosis as the disease may mimic tuberculosis(TB) and other causes of hepatosplenomegaly such as visceral leishmaniasis. Laboratory diagnosis includes culture, direct staining, antigen and antibody detection. Antibody detection may give false negative in the immunocompromised patient. The infection responds well to antifungal agents (amphotericin B is the drug of choice) and life long maintenance therapy may be required in AIDS especially if CD4 counts remain less than 150 cells/microlitre. Histoplasmosis should be a differential diagnosis in immunosuppressed patients with unexplained fever, weight loss, hepatosplenomegaly and chest findings especially if not responding to anti-TB treatment.
Insights
Histoplasmosis, a fungal infection, often presents as disseminated disease in immunocompromised patients, including those with acquired immune deficiency syndrome (AIDS). Early diagnosis and antifungal treatment are crucial for managing this opportunistic infection.
Area of Science:
- Mycology
- Infectious Diseases
- Immunology
Background:
- Histoplasmosis is a systemic fungal infection caused by dimorphic fungi, Histoplasma capsulatum variants.
- It is globally distributed, with higher prevalence in North America and Central America, and also occurs in Africa.
- The disease spectrum ranges from asymptomatic infection to disseminated disease, particularly in immunocompromised individuals.
Observation:
- Four cases of disseminated histoplasmosis in two infants and two adults are presented.
- All cases involved multiple organs and were not clinically suspected, with diagnosis made incidentally on bone marrow aspirate cytology.
- Two adult cases were HIV-positive; one was not on highly active anti-retroviral therapy (HAART) and had a low CD4 count, while the other was on HAART with undetermined CD4 count.
Findings:
- Disseminated histoplasmosis can mimic other conditions like tuberculosis and visceral leishmaniasis, necessitating a high index of suspicion.
- Laboratory diagnosis involves culture, staining, antigen, and antibody detection, though antibody tests may yield false negatives in immunocompromised patients.
- The infection responds to antifungal agents like amphotericin B, with potential need for lifelong maintenance therapy in AIDS patients with low CD4 counts.
Implications:
- Histoplasmosis should be considered in immunocompromised patients presenting with unexplained fever, weight loss, hepatosplenomegaly, and chest findings, especially if unresponsive to anti-tuberculosis treatment.
- Prompt diagnosis and appropriate antifungal therapy, including potential long-term maintenance, are vital for managing histoplasmosis in immunocompromised populations.
- This highlights the importance of considering opportunistic infections like histoplasmosis in the differential diagnosis of severe febrile illnesses in individuals with compromised immune systems.
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