[Disseminated histoplasmosis in a woman with seronegative arthritis].

Histoplasma capsulatum is an environmental fungus commonly found in the Ohio and Mississippi River valleys, Central and South America, and Asia. The most affected areas in Argentina are the Paraná and de La Plata river basins. Patients with histoplasmosis can have a wide range of clinical presentations. Most of them are asymptomatic, while those with compromised cellular immunity are at increased risk for the disseminated form. We present the case of a patient undergoing treatment with methotrexate for seronegative arthritis who developed the disseminated form of the disease, and who represented a diagnostic challenge due to the difficulty in identifying the etiologic agent.