Histoplasmosis - Chronic Pulmonary

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Overview, Causes, & Risk Factors

Histoplasmosis is caused by a fungus found in the soil of the central and eastern United States (especially Mississippi and Ohio river valleys), eastern Canada, Mexico, Central America, and South America. The primary infection (acute histoplasmosis) usually causes no symptoms (asymptomatic), or only mild disease that is easily cleared by an intact immune system.

Chronic pulmonary histoplasmosis occurs in individuals with structurally abnormal lungs, such as smokers with emphysema or COPD. In these individuals, the acute infection with histoplasmosis smolders and progresses causing symptoms and chest X-ray findings that mimic pulmonary tuberculosis.

Although many of these infections eventually resolve, some infections in these abnormal lung spaces persist causing enlargement of existing emphysematous lung spaces and destroying adjacent more normal lung tissue. Scarring (fibrotic changes) and cavities may occur as a result of this chronic infection.

Risk factors include: travel or residence in central or eastern United States; environmental or occupational exposure to soil or particles contaminated with droppings of chickens, bats, or blackbirds; preexisting COPD (chronic obstructive pulmonary disease); and people whose immune systems have been suppressed by disease (such as AIDS) or medication.