Chapter 4--histoplasmosis.

Histoplasmosis is systemic mycosis caused by a small fungus, Histoplasma capsulatum var. capsulatum, whose natural habitat is soil contaminated by bat or bird excrement. The incidence of histoplasmosis is worldwide. In Brazil, the disease is found in all regions; however, the state of Rio de Janeiro is responsible for most of the microepidemics described. Human infection occurs when airborne spores of H. capsulatum are inhaled. The most common clinical presentation is asymptomatic. The symptoms of acute or epidemic histoplasmosis are high fever, cough, asthenia and retrosternal pain, as well as enlargement of the cervical lymph nodes, liver and spleen. The most common radiological findings are diffuse reticulonodular infiltrates in both lungs, as well as hilar and mediastinal lymph node enlargement. In chronic pulmonary histoplasmosis, the clinical and radiological manifestations are identical to those of reinfection with pulmonary tuberculosis. Histoplasmosis is diagnosed by means of the identification or culture growth of the fungus in sputum or fiberoptic bronchoscopy specimens. Histopathological examination reveals the fungus itself within or surrounding macrophages, as well as granulomatous lesions with or without caseous necrosis. Double agar gel immunodiffusion is the most easily used and readily available serologic test for making the immunological diagnosis. Acute histoplasmosis with prolonged symptoms requires treatment, as do the disseminated or chronic pulmonary forms of the disease. The drug of choice is itraconazole.