Unmasking Histoplasmosis: A Diagnostic Challenge of Pediatric Febrile Neutropenia in an Immunocompromised Patient.

Histoplasmosis is an infection caused by a dimorphic fungus. Disseminated disease in children is described mainly in infants under two years of age, but can be particularly aggressive in immunocompromised patients. We report the case of a six-year-old girl with B-cell acute lymphoblastic leukemia (ALL) who presented with fever of unknown origin, respiratory symptoms, hepatosplenomegaly, and pancytopenia. She was admitted to the hospital with febrile neutropenia and exhibited a progressively worsening clinical course. Initial work-up, including laboratory and imaging studies, failed to identify a clear infectious source. Due to signs of respiratory compromise, a chest computed tomography (CT) was performed, revealing interstitial pneumonia. A bone marrow aspirate subsequently identified intracellular budding yeast, which was confirmed as Histoplasma capsulatum by polymerase chain reaction (PCR) testing. The diagnosis of disseminated histoplasmosis was established, and treatment with intravenous liposomal amphotericin B was initiated, resulting in a favorable clinical response. The patient has now been in remission from leukemia and off treatment for one year since this infectious episode.