Clinical course following exposure to Histoplasma capsulatum

Histoplasmosis remains asymptomatic in most healthy individuals following low level exposure. Symptomatic infection usually causes self-limited pulmonary illnesses, rheumatologic manifestations, erythema nodosum, or pericarditis, but a heavy inoculum can cause diffuse pulmonary involvement. The variation in clinical course noted in the illustration above depends on the extent of exposure to the organism (ie, ~1 percent of individuals exposed to a low inoculum develop self-limited symptomatic infection compared with ~50 percent of individuals exposed to a high inoculum). Persons with emphysema may develop chronic pulmonary histoplasmosis with cavity formation, and individuals at the extremes of age or with underlying immunosuppressive conditions can develop progressive disseminated disease. Rarely, patients manifest chronic inflammatory conditions such as fibrosing mediastinitis or a sarcoidosis-like illness.