Diagnostic approaches to severe, atypical toxoplasmosis mimicking acute retinal necrosis.

To describe the means of diagnosis and clinical features of atypical toxoplasmic chorioretinitis mimicking acute retinal necrosis. Observational case series. Twenty-two patients (25 eyes) with widespread chorioretinitis resulting from toxoplasmosis examined between 1990 and 2001. Patients were diagnosed by various techniques, including polymerase chain reaction (PCR) of aqueous and vitreous, serum and intraocular antibody determination, culture of intraocular fluid, retinal biopsy, histopathologic examination, therapeutic trial of antibiotics active against toxoplasmosis, or a combination thereof. The primary outcome measure was diagnosis of disseminated toxoplasmic chorioretinitis by any combination of tests or by empiric use of specific antibiotics. The secondary outcome measure was visual and anatomic outcome of treatment. Mean age was 53.5 years (range, 19-77 years), with a median of 59.5 years. There were 9 women and 13 men. Six patients were infected with HIV, and 3 patients, 1 with HIV, had bilateral disease. Mean initial vision was 20/110 (median, 20/400; range, 20/20 to no light perception [NLP]). Sixteen patients (73%) had received oral or injectable corticosteroids and 11 (50%) had received antiviral therapy before the diagnosis of toxoplasmosis. Diagnosis was made solely by clinical response to antitoxoplasmosis medications in 4 patients. Sixteen patients were diagnosed based on evaluation of intraocular fluids and tissue by antibody determinations, culture, PCR, histopathologic examination, or a combination thereof. Visual acuity improved after treatment in 7 of 25 eyes (28%). Mean final visual acuity was 20/156 (median, 20/2500; range, 20/30 to NLP). Anatomically, 18 of 23 eyes with follow-up had healed or improved chorioretinitis. Retinitis was progressive in 1 eye, 2 eyes were enucleated, and 2 were phthisical. Diagnosis of atypical toxoplasmic chorioretinitis that mimics viral retinitis can be accomplished by several means. Prompt diagnosis may help avoid poor visual and anatomic outcomes after prolonged initial treatment with oral prednisone or antiviral medications.