Toxoplasmic chorioretinitis may be diagnosed as a congenital or postnatally acquired disease due to primary infection or reactivation of latent infection. Toxoplasmosis causes an acute focal retinitis in which the hallmark is a thickened cream-colored retina accompanied by an overlying intense vitreal inflammatory reaction ("headlight in the fog appearance"). Recurrent lesions are usually seen at the borders of chorioretinal scars (Fig. 1C). Primary ocular infections are less common than reactivation of old lesions. Based on seroprevalence data, the overall incidence of infection with Toxoplasma gondii ranges from 22.5% in the United States to 75% in El Salvador. In immunocompetent individuals, the primary infection is usually asymptomatic, although a small percentage of individuals will develop chorioretinitis, lymphadenitis, myocarditis, or polymyositis. An unfavorable, life-threatening course of toxoplasmosis would be expected only in persons with impaired T-cell-mediated immunity, such as those with acquired immunodeficiency syndrome, bone marrow transplant patients, and recipients of solid organ allografts. In immunocompromised patients, toxoplasmosis can result in fever, malaise, and severe central nervous system (CNS) disturbances, including confusion, seizures, focal neurologic deficits, and spinal cord myelopathy, as well as chorioretinitis as a presenting feature (9).
Whipple's disease is caused by rod-shaped bacteria called Tropheryma whippelii. This infection involves the eyes in about 5% of patients, causing uveitis and retinitis, as well as vitritis, papilledema, and direct involvement of the lens epithelium. Whipple's disease is extraordinarily rare. Lymphadenopathy is frequent and may involve the cervical nodes. Other common symptoms are fever, weight loss, diarrhea, and arthritis. Whipple's disease may also affect the cardiovascular, pulmonary, and CNSs, and produce anemia, hypo-albuminemia, and thrombocytosis (10).
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