A chronic respiratory infection caused by inhaling the spores of the fungus, Histoplasma capsulatum, found commonly in the soil of endemic regions, such as states along the Mississippi or Ohio river valleys.
Alternative Names
Chronic cavitary histoplasmosis
Causes, incidence, and 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.
Signs and tests
Tests that may be used in the diagnosis of chronic pulmonary histoplasmosis include:
chest X-ray chest CT scan sputum culture and stain biopsy of infected tissue, such as open lung biopsy, or bone marrow biopsy
bronchoscopy with transtracheal biopsy or bronchoalveolar lavage Histoplasma complement fixationtiter a Histoplasma urinary antigen test Immunodiffusion test for precipitating antibodies to antigens of histoplasma CBC
Expectations (prognosis)
The infection usually responds to antifungal medication, but the fibrotic changes within the lung often remain. Prognosis for chronic pulmonary histoplasmosis is favorable, but many patients continue to be ill due to their pre-existing emphysematous lung disease. Rarely, pulmonary histoplasmosis can progress to disseminated histoplasmosis, affecting many other organs, such as bones, joint, liver, eye, and bone marrow. Progression to disseminated histoplasmosis has a less favorable prognosis.
Complications
histoplasmosis; disseminated spreading of the infection through the blood to other organs (especially likely in immunosuppressed people or in very young children)
respiratory insufficiency lung scarring (fibrosis) pericarditis arthritis
Calling your health care provider
Call for an appointment with your health care provider if symptoms of chronic pulmonary histoplasmosis develop. Call your health care provider if symptoms continue despite treatment, or if breathing difficulty or symptoms of disseminated histoplasmosis occur.
Prevention
Avoiding travel to areas where this spore is found would prevent it, but this is not practical. Avoid bird or bat droppings if you are in one of these areas, especially if you are immunosuppressed .