Disseminated histoplasmosis in a 4-month-old infant presenting with prolonged fever and pancytopenia: A case report

Background: Histoplasmosis is the most prevalent endemic mycosis in the United States, typically affecting immunocompromised individuals. Diagnosis of histoplasmosis in immunocompetent patients is rare, particularly among young infants, with only a few cases reported. Case presentation: We present a 4-month-old female with a history of prematurity who initially presented with 11 days of fever. She visited her local emergency department, where she was diagnosed with Rhino/ enterovirus bronchiolitis. Pancytopenia was noted at that time, attributed to viral bone marrow suppression. Persistent fever and pancytopenia led to her transfer to our hospital for further evaluation and treatment. On admission, she exhibited hepatosplenomegaly, pancytopenia, elevated procalcitonin, and lactate dehydrogenase levels. Additionally, T cell deficiency was observed. Initially, there was concern for hemophagocytic lymphohistiocytosis; however, bone marrow biopsy and aspirate confirmed T cell deficiency. As fever persisted on day 19, further investigations were conducted, including a positive beta-D-glucan assay. Subsequent urine and serum Histoplasma antigen tests were positive, with metagenomic sequencing confirming the diagnosis of histoplasmosis. Treatment comprised one week of amphotericin B followed by three months of oral itraconazole. Resolution of fever, pancytopenia, T cell deficiency, and hepatosplenomegaly occurred, and the patient has shown no signs of recurrence to date. Conclusions: This case serves as a reminder to clinicians regarding the necessity of considering disseminated histoplasmosis in young infants who present with fever of unknown origin, pancytopenia, and hepatosplenomegaly, despite its rarity. Failure to do so can lead to fatal outcomes. (c) 2025 Published by Elsevier Masson SAS on behalf of SFMM.