[Toxoplasmic chorioretinitis: positive PCR on vitreous with negative serology for Toxoplasma gondii].

Ocular recurrences of congenital toxoplasmosis usually occur during the first and second decades of life. At that time, serum levels of IgG against toxoplasmosis are almost always detectable because of the very high sensitivity of the test. The diagnosis is mainly supported by the ophthalmological examination and the good clinical response to treatment. In atypical cases, the Goldman-Witmer coefficient (GWC) on aqueous and polymerase chain reaction (PCR) on aqueous or vitreous is usually performed to substantiate the diagnosis. We report a case of recurrent macular chorioretinitis in a 13-year-old immunocompetent patient with a history of congenital toxoplasmosis whose repeated serologies remained negative or uncertain. However, the diagnosis of toxoplasmic chorioretinitis was supported by the detection of Toxoplasma gondii DNA by PCR analysis in a vitreous sample. Although the sensitivity of serology is very high, it is not perfect and there are false-negative results. In case of high clinical presumption in spite of a negative serology, PCR could be a helpful contribution to the diagnosis.