Histoplasmosis
Also called Ohio Valley disease, Central Mississippi Valley disease, Appalachian Mountain disease, and Darling’s disease, histoplasmosis occurs in the United States in three forms: primary acute histoplasmosis, progressive disseminated histoplasmosis (also known as acute disseminated or chronic disseminated disease), and chronic pulmonary (cavitary) histoplasmosis. The last form produces cavitations in the lung similar to those seen in pulmonary tuberculosis. A fourth form, African histoplasmosis, occurs only in Africa and is caused by the fungus Histoplasma capsulatum var. duboisii.
Histoplasmosis occurs worldwide, especially in the temperate areas of Asia, Africa, Europe, North America, and South America. In the United States, it’s most prevalent in the central and eastern states, especially in the Mississippi and Ohio river valleys.
Probably because of occupational exposure, histoplasmosis is more common in males than in females. Fatal disseminated disease occurs more commonly in infants and elderly males.
The incubation period ranges from 5 to 18 days, although chronic pulmonary histoplasmosis may progress slowly for many years. The prognosis varies with each form. The primary acute form is benign, but the progressive disseminated form is fatal in about 90% of patients. Without proper chemotherapy, chronic pulmonary histoplasmosis is fatal in about 50% of patients within 5 years.
Causes
Histoplasmosis is caused by H. capsulatum, which is found in the feces of birds and bats and in soil contaminated by their feces, such as that near roosts, chicken coops, barns, caves, and under bridges.
Transmission occurs through inhalation of H. capsulatum or H. capsulatum var. duboisii spores or through the invasion of spores after minor skin trauma.
Complications
Possible complications include vascular or bronchial obstruction, acute pericarditis, pleural effusion, mediastinal fibrosis or granuloma, intestinal ulceration, Addison’s disease, endocarditis, and meningitis.
Assessment
The patient’s history may reveal an immunocompromised condition or exposure to contaminated soil in an endemic area.
The severity of symptoms depends on the size of the inhaled inoculum and the immune condition of the host. Also, symptoms vary with the form of the disease. For example, a patient with primary acute histoplasmosis may be asymptomatic, or he may complain of a mild respiratory
illness similar to a severe cold or influenza. He may also report malaise, headache, myalgia, anorexia, cough, and chest pain. A patient with progressive disseminated histoplasmosis may complain of anorexia, weight loss and, possibly, pain, hoarseness, and dysphagia. A patient with chronic pulmonary histoplasmosis may have symptoms that mimic pulmonary tuberculosis. He may complain of a productive cough, dyspnea, and occasional hemoptysis. He’ll eventually experience weight loss and breathlessness.
illness similar to a severe cold or influenza. He may also report malaise, headache, myalgia, anorexia, cough, and chest pain. A patient with progressive disseminated histoplasmosis may complain of anorexia, weight loss and, possibly, pain, hoarseness, and dysphagia. A patient with chronic pulmonary histoplasmosis may have symptoms that mimic pulmonary tuberculosis. He may complain of a productive cough, dyspnea, and occasional hemoptysis. He’ll eventually experience weight loss and breathlessness.
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