The disease caused by Histoplasma, histoplasmosis, may be asymptomatic and diagnosed incidentally as a "coin lesion" on chest X-ray. It has the potential to cause acute or chronic pulmonary infection. This can occur in workers exposed to a large inoculum in construction or cave excavation. H. capsulatum causes lung infections in those with weakened immune systems. Disturbed fungal spores are inhaled. In most healthy individuals, the immune system walls off the invader (creating a lung lesion) - rendering the fungus inactive. The immunocompromised are at risk for disseminated histoplasmosis following pulmonary infection. Disseminated infection may lead to oropharyngeal ulcers, hepatic and/or splenic involvement, or infection of the bone marrow, CNS, major arteries, or cardiac valves.
H. duboisii causes the disease African histoplasmosis, which involves skin and bones and rarely the lungs.
Disseminated histoplasmosis can be diagnosed with an antigen test performed on urine or serum.
