Acute Retinal Lesion From Toxoplasmosis

An 18-year-old woman presented with diminished vision and recent onset of floaters in the right eye. Her medical and ocular histories were noncontributory.

An ophthalmologic examination revealed mildly decreased visual acuity in the right eye. There was no iritis, but dilated fundus evaluation indicated a vitritis-an area of retinal yellowish whitening with elevation and adjacent retinal vein inflammation. The retinal and vitreous changes were diagnosed as toxoplasmic retinochoroiditis.

Dr Leonid Skorin, Jr, of Dixon, Ill, writes that unilateral and solitary ocular lesions that display little pigment deposition result from acute acquired toxoplasmosis, whereas congenital ocular toxoplasmosis is usually bilateral. Most ocular lesions are located in the posterior pole, particularly in the macular region. Ocular toxoplasmosis typically involves the inner retina and is associated with a marked vitreous reaction. As many as one quarter of all posterior uveitis cases may be attributed to toxoplasmosis. Acute lesions are yellowish white, elevated patches with blurred borders. They may heal spontaneously after several weeks or months and produce a well-demarcated chorioretinal scar with bare sclera often surrounded by hypertrophic retinal pigment epithelium. Reactivated disease may provoke the appearance of satellite lesions next to old scars.

Toxoplasmosis is caused by the protozoon Toxoplasma gondii, which infects both humans and animals. The common routes of transmission to humans are ingestion of contaminated food or undercooked meat, inhalation of the oocysts of the parasite shed in cat stool, and intrauterine infection to the fetus of an infected mother. This patient denied eating raw meat but did keep several cats as pets.

Treatment for ocular toxoplasmosis is only indicated if the patient's vision is affected adversely or if the lesion is threatening the optic nerve or macula. Any of a number of antitoxoplasmic agents may be prescribed, including pyrimethamine, sulfadiazine, clindamycin, tetracycline, or trimethoprim-sulfamethoxazole (TMP-SMX). Significant inflammation is treated with oral prednisone in conjunction with antimicrobial therapy. This patient's infection responded to treatment with clindamycin, TMP-SMX, and prednisone.