Natural history of experimental histoplasmic choroiditis in the primate. II. Histopathologic features.

The histopathologic features of experimental multifocal histoplasmic choroiditis in the primate are presented. Eyes were studied at various time periods from 30 days to 3 years after intracarotid injection with live Histoplasma capsulatum organisms. The acute lesions produced resolved into four distinct resolution patterns (chorioretinal scars, retinal pigment epithelial defects, subclinical lesions, and "disappearing" lesions) whose histopathologic features were studied. Organisms could not be demonstrated by culture or special stains in lesions present more than 6 weeks. A feature common to all eyes studied, including those whose lesions were clinically inactive or had clinically "disappeared," was the persistence of small foci of lymphocytes in the choroid. Damage to Bruch's membrane was observed in some specimens.