Hemophagocytic lymphohistiocytosis secondary to disseminated histoplasmosis diagnosed by bone marrow smear microscopy and metagenomic next-generation sequencing: A case report and review of literature.

Hemophagocytic lymphohistiocytosis (HLH) secondary to Histoplasma capsulatum infection is rare in immunocompetent individuals but is associated with an extremely high mortality rate. Here, we report a case of disseminated histoplasmosis (DHP) in an immunocompetent patient. The pathogen was confirmed by bone marrow smear microscopy and metagenomic next-generation sequencing (mNGS). The patient experienced rapid clinical deterioration and was subsequently diagnosed with HLH secondary to DHP. Following targeted antimicrobial therapy with amphotericin B and immunomodulatory treatment involving etoposide and ruxolitinib, the patient's clinical condition improved. Early clinical manifestations of DHP are often atypical, while conventional diagnostic methods frequently yield negative results in the early stage. This case indicates that bone marrow examination combined with mNGS facilitates early definitive diagnosis. Furthermore, this report rarely describes the sequential morphological changes of Histoplasma capsulatum in bone marrow tissue.