438  “Rapid Identification of Disseminated Histoplasmosis by Peripheral Blood Smear: A Three-Case Series”

Introduction/Objective Disseminated histoplasmosis is a life-threatening fungal infection predominantly affecting immunocompromised patients. While bone marrow biopsy and fungal cultures are standard diagnostics, identification of Histoplasma capsulatum on peripheral blood smear (PBS) is rare. We report three cases of disseminated histoplasmosis diagnosed on PBS within a three-month period at our institution, highlighting an unusual cluster and the diagnostic value of PBS. Methods/Case Report We retrospectively reviewed clinical data, PBS findings, diagnostic timing, and outcomes for three patients diagnosed between March and June 2024. Results The patients included a kidney transplant recipient, a person with HIV, and a patient with hemophagocytic lymphohistiocytosis. PBS revealed intracellular yeast forms consistent with Histoplasma in all cases, prompting early antifungal treatment. Despite therapy, two patients died from fungal sepsis and multi-organ failure; one improved. PBS findings were confirmed by fungal culture or histopathology. Conclusion This cluster underscores the utility of PBS for early identification of disseminated histoplasmosis in high-risk patients. Recognizing Histoplasma on PBS can expedite diagnosis and treatment, potentially improving clinical outcomes in critically ill immunocompromised patients.