Prolonged Disseminated Magnusiomyces capitatus Infection in a Neutropenic Patient: A Case Report

Aim and background: <i>Magnusiomyces capitatus</i> is a commensal environmental pathogen that has been reported to cause life-threatening disease in immunosuppressed patients, most frequently associated with leukemia. The majority of cases have been documented at the case report level, although there are retrospective data demonstrating that disseminated fungemia has been shown to have a mortality approaching 70%. Inherent resistance to echinocandins and the above-noted rarity of this pathogen make treatment difficult. There is an even greater paucity of literature surrounding the treatment of this pathogen in pediatric patients as well as concomitant usage of granulocyte colony-stimulating factor (G-CSF). Case description: We present the case of an 8-year-old patient who had a pertinent medical history of acute myeloid leukemia (AML). He presented with febrile neutropenia during his last course of chemotherapy. He was found to have disseminated <i>M. capitatus</i> infection with fungemia, with hepatosplenic and pulmonary involvement. Initial blood cultures were positive for yeast at 24 hours, but based on negative rapid polymerase chain reaction (PCR) testing for <i>Candida</i> and Gram stain appearance, atypical yeast was suspected, and he was empirically started on a broad, multidrug antifungal regimen. With subsequent speciation, this was changed to amphotericin and voriconazole, with later addition of flucytosine. Despite prompt administration of antifungal therapy before speciation of the yeast and rapid removal of the central venous catheter, the patient remained persistently fungemic for 9 days prior to clearance. He also developed septic shock and respiratory failure requiring vasopressor support, mechanical ventilation, and continuous renal replacement therapy (CRRT). Sargramostim and filgrastim were added due to clinical severity and persistent neutropenia. Following a prolonged intensive care admission and hospitalization, he was able to be discharged home on enteral voriconazole. Clinical significance: Prompt diagnosis and treatment of atypical fungal infections remain a challenge; definitive diagnosis and speciation often take time, optimal antifungal regimens are less well defined, and the need for adjunctive therapies, such as granulocyte-stimulating factors, is unclear. With increased utilization of PCR-based assays for the rapid identification of pathogens, inability to identify more common yeasts should raise suspicion for more exotic and resistant organisms, such as <i>M. capitatus</i>. How to cite this article: Nevin A, Mohanty V, Smink G, <i>et al.</i> Prolonged Disseminated <i>Magnusiomyces capitatus</i> Infection in a Neutropenic Patient: A Case Report. Pediatr Inf Dis 2025;7(4):138–140.