Histoplasmosis

Histoplasmosis is a fungal infection caused by Histoplasma capsulatum. This disease may also be called Ohio Valley, Central Mississippi Valley, Appalachian Mountain, or Darling’s disease. In the United States, it occurs in three forms: primary acute histoplasmosis, progressive disseminated histoplasmosis (acute disseminated or chronic disseminated disease), and chronic pulmonary (cavitary) histoplasmosis, which 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.

The prognosis varies with each form. The primary acute disease is benign; the progressive disseminated disease is fatal in approximately 90% of patients; and, without proper chemotherapy, chronic pulmonary histoplasmosis is fatal in 50% of patients within 5 years.

Causes

H. capsulatum is found in the feces of birds and bats or in soil contaminated by their feces, such as that found near roosts, chicken coops, barns, or caves or underneath bridges. Transmission occurs through inhalation of H. capsulatum or H. duboisii spores or through the invasion of spores after minor skin trauma. Possibly, oral ingestion of spores may cause the disease.

The incubation period is from 5 to 18 days, although chronic pulmonary histoplasmosis may progress slowly for many years. Histoplasmosis is more common in adult men, likely due to occupational exposure. Fatal disseminated disease, however, is more common in infants and elderly men.

Histoplasmosis occurs worldwide, especially in the temperate areas of Asia, Africa, Europe, and North 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.

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 Findings

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