Histoplasmosis: No Longer Just a Disease of the Immunocompromised

Histoplasmosis is a fungal infection primarily caused by the dimorphic fungus Histoplasma capsulatum. In endemic regions, the primary reservoirs are soil and the waste of bats and birds. The fungus spreads through the inhalation of spores in contaminated environments, often behaving as an opportunistic pathogen. Its clinical presentation is highly variable, ranging from asymptomatic cases to progressive disseminated infections, which can be fatal if left untreated. A 56-year-old man with a history of pulmonary emphysema, previous oral candidiasis, and frequent travel to Asia presented with splenomegaly, hepatosplenomegaly, leukopenia, and thrombocytopenia. An extensive diagnostic workup ruled out HIV, tropical infections, and storage diseases but revealed elevated levels of angiotensin-converting enzyme and β2 microglobulin. Imaging studies showed emphysematous changes, mediastinal adenopathy, and tree-in-bud opacities. Bronchofibroscopy identified mucosal nodular lesions, which, upon biopsy, were confirmed to be necrotizing granulomas with fungal morphology consistent with Histoplasma. The diagnosis of progressive disseminated histoplasmosis involving the lungs, bone marrow, and spleen was established. Treatment with intravenous amphotericin B led to clinical and radiological improvement. This case underscores the importance of considering disseminated histoplasmosis in immunocompetent patients, even in nonendemic areas. It highlights the critical role of thorough clinical history and prompt diagnosis in ensuring effective management.