Disseminated histoplasmosis in an immunocompetent Nigerian child diagnosed on a peripheral blood smear

Abstract

Disseminated histoplasmosis is commonly associated with immunocompromised individuals but can also affect immunocompetent persons. However, the diagnosis may be missed as is often not expected in the non-immunocompromised. Our case report highlights the need to consider histoplasmosis as a differential in immunocompetent individuals. A 17-year-old female with symptoms of persistent fever and fatigue of 3 weeks duration. Examination findings were significant pallor, jaundice, and cervical lymphadenopathy. The chest X-ray, stool for Gene Xpert and urine for lipoarabinomannan assay were not supportive of tuberculosis. The retroviral screening was negative. Blood culture yielded no pathogen. A complete blood count showed leukocytosis with anaemia. The reticulocyte count was greater than 2%. Initial peripheral blood smear showed, neutrophilia with toxic granulations and atypical lymphocytes. However, as the fever was unrelenting, a repeat blood smear was requested which revealed numerous yeast cells with a narrow budding base and tuberculated macroconidia morphologically similar to Histoplasma capsulatum. A diagnosis of disseminated histoplasmosis was made and the patient was commenced on itraconazole. The fever abated and the anaemia resolved. The patient was to be followed up in the clinic a month later. Her complete blood count levels were now within normal, and a repeat peripheral blood smear showed no atypical lymphocytes. This case report affirms the need to promptly diagnose and initiate appropriate treatment in a patient with invasive mycosis and the role of microscopy in a setting where classical diagnostics are not routinely available.