Tissue morphology of Histoplasma capsulatum in acute histoplasmosis.

Reports of histopathology in acute histoplasmosis are rare. A case of fulminating acute histoplasmosis with hematogenous dissemination is described in which Histoplasma capsulatum was identified in transbronchial biopsy. This report represents the first morphologic description of H. capsulatum within human pulmonary tissue in the early phase of acute histoplasmosis. The yeast forms observed were of typical size, but they were present within the alveoli and were budding. No tissue granulomata were noted. This unusual morphology is in sharp contrast to the classic description of the organism in tissues and presented diagnostic difficulties, which are discussed in this report. Hematogenous dissemination is considered to be an important part of the pathogenesis of the disease, but it is rarely documented during the symptomatic phase of acute histoplasmosis. Cultural documentation of hematogenous dissemination was obtained in this patient. These observations stress the importance of obtaining culture material from extrapulmonary sites early in the course of acute histoplasmosis when a specific diagnosis is necessary.