Histoplasmosis

A disease caused by the fungus Histoplasma capsulatum. Most people with histoplasmosis have no symptoms. However, histoplasma can cause acute or chronic lung disease and progressive disseminated histoplasmosis affecting a number of organs. It can be fatal if untreated. Positive skin tests to Histoplasma occur in as many as 80% of the people living in areas where the fungus is common, such as the eastern and central United States. Infants, young children, and older persons, in particular those with chronic lung disease are at increased risk for severe disease. Disseminated disease is more frequently seen in people with cancer or AIDS. The fungus grows in soil and material contaminated with bat or bird droppings. Spores become airborne when contaminated soil is disturbed. Breathing the spores causes infection. The disease is not transmitted from an infected person to someone else. Symptoms start within 3 to 17 days after exposure; the average is 10 days. The acute respiratory disease is characterized by respiratory symptoms, a general ill feeling, fever, chest pains, and a dry or nonproductive cough. Distinct patterns may be seen on a chest x-ray. Chronic lung disease resembles tuberculosis and can worsen over months or years. The disseminated form is fatal, unless treated. Mild cases resolve without treatment. Severe cases of acute histoplasmosis and all cases of chronic and disseminated disease are treated with with antifungal medications, usually for life in those with compromised immune systems.

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A widely distributed infectious disease caused by Histoplasma capsulatum and occurring occasionally in outbreaks; usually acquired by inhalation of spores of the fungus in soil dust and manifested by a self-limited pneumonia. In patients with emphysema, infection may be chronic and cause pulmonary fibrocavitary disease resembling tuberculosis; in immunosuppressed patients and, rarely, in normals, h. may cause disseminated disease of the reticuloendothelial system, which is manifested by fever, emaciation, splenomegaly, and leukopenia. SYN: Darling disease.

- acute h. caused by inhalation of microconidia, resulting in illness ranging from flulike to the acute diffuse pneumonitis seen with heavy exposure. Often, following illness, lesions heal, leaving calcified nodules.

- African h. a form of h. caused by the fungus Histoplasma capsulatum var. duboisii, observed only in tropical Africa; infection is manifest as chronic granulomatous lesions in bone, skin, and other organs.

- chronic h. disease usually seen in patients with underlying abnormal lung parenchyma, particularly emphysema and bullous lung disease. The disease is indolent, characterized by cough and sputum production, and radiographically by gradual loss of lung volume.

- chronic mediastinal h. mediastinal fibrosis caused by lymph node involvement by h.. Can cause a huge fibrotic mass involving many critical structures in the mediastinum.

- disseminated h. widespread infection that involves many organs; occurs in infants and immunocompromised patients, such as those with AIDS.

- presumed ocular h. subretinal neovascularization in the macular region associated with chorioretinal atrophy and pigment proliferation adjacent to the optic disk, and peripheral chorioretinal atrophy (“histo-spots”).

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his·to·plas·mo·sis -.plaz-'mō-səs n, pl -mo·ses -.sēz a respiratory disease with symptoms like those of influenza that is endemic in the Mississippi and Ohio river valleys of the U.S., is caused by infection with a fungus of the genus Histoplasma (H. capsulatum), and is marked by benign involvement of lymph nodes of the trachea and bronchi usu. without symptoms or by severe progressive generalized involvement of the lymph nodes and macrophage-rich tissues (as of the liver and spleen) with fever, anemia, leukopenia and often with local lesions (as of the skin, mouth, or throat)

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n.

an infection caused by inhaling spores of the fungus Histoplasma capsulatum. The primary pulmonary form usually produces no symptoms or harmful effects and is recognized retrospectively by X-rays and positive histoplasmin skin testing. Occasionally, progressive histoplasmosis, which resembles tuberculosis, develops. The fungus may spread via the bloodstream to attack other organs, such as the liver, spleen, lymph nodes, or intestine. Symptomatic disease is treated with intravenous amphotericin. The spores are found in soil contaminated by faeces, especially from chickens and bats. The disease is endemic in the northern and central USA, Argentina, Brazil, Venezuela, and parts of Africa.

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his·to·plas·mo·sis (his″to-plaz-moґsis) infection resulting from inhalation, or sometimes ingestion, of spores of Histoplasma capsulatum. It is usually asymptomatic, but in a few cases it may cause acute pneumonia, disseminated reticuloendothelial hyperplasia with hepatosplenomegaly and anemia, or an influenzalike illness with joint effusion and erythema nodosum. Reactivated infection, such as in immunocompromised patients, involves the lungs, meninges, heart, peritoneum, and adrenals, in that order of frequency. Called also Darling disease.