Toxoplasmic retinochoroiditis: electron-microscopic and immunofluorescence studies of formalin-fixed tissue
N. A. Rao and R. L. Font
An 82-year-old white man had bilateral, chronic recurrent uveitis caused by
Toxoplasma gondii. In spite of extensive therapy for toxoplasmosis, the
left eye became painful and blind and was enucleated. Histopathologically,
the retina disclosed unusually large numbers of necrotic cysts and a few
presumably viable cysts containing crescent-shaped organisms and scanty
free forms of T gondii. Electron-microscopic studies confirmed the presence
of a true wall of the cysts as well as additional ultrastructural features
highly characteristic of the parasite. Immunofluorescent studies of the
formalin-fixed tissue demonstrated quite vividly the cysts, which stained
variably according to the stage of viability of the organisms. In cases in
which toxoplasmic retinochoroiditis has been suspected clinically but
routine histologic preparations fail to reveal the organisms, the remaining
formalin-fixed tissue should be examined by specific immunofluorescent
methods to demonstrate antigenic material of the causative parasite.
