Histoplasmosis in a Brazilian center: clinical forms and laboratory tests

Histoplasmosis, caused by the dimorphic fungus Histoplasma capsulatum, is endemic in many regions of the Americas, Asia and Africa. It has a wide spectrum of clinical manifestations, from asymptomatic infection to severe disseminated disease. A retrospective study was carried out to describe the clinical forms and assess the clinical significance of the laboratory diagnostic tests of patients with histoplasmosis during the period of July 1987 to December 2003 at Instituto de Pesquisa Clínica Evandro Chagas/ FIOCRUZ, RJ, Brazil. Seventy-four patients were included. Forty-nine percent of the cases (n = 36) occurred in HIV positive patients who presented with disseminated disease. The remaining 38 cases were classified in different clinical forms. Histoplasma capsulatum was isolated from 69.5% of the clinical specimens sent to culture. Immunodiffusion and immunoblot were positive in 72.6% and 100% of the performed tests, respectively. Histopathologic findings suggestive of H. capsulatum were found in 63.2% of the performed exams. Serology had a lower proportion of positivity amongst AIDS patients, when compared with HIV negative patients (X2 = 6.65; p lower than 0.008). Statistical differences between AIDS and non-AIDS patients were not observed with culture and histopathology. The specific role of each test varies according to the clinical form. Physicians need to know the value and limitations of the available diagnostic tests, but before that, they have to think about histoplasmosis and consider this clinical entity in their differential diagnosis.