Purpose: Retinochoroiditis is generally diagnosed after the first year of life and the association with congenital toxoplasmosis presents a diagnostic dilemma. The detection of local intraocular specific antibodies could be useful for diagnosis.
Methods: We studied six patients (mean age 7 +/- 5 years) with retinochoroiditis which appeared after the first year of life. Aqueous and serum were analysed by immunoblotting for anti T. gondii IgG to diagnose toxoplasmosis.
Results: All serum samples were positive only for anti T. gondii IgG. The retinochoroiditis was active in three patients and inactive in the others. Immunoblot analysis of serum and aqueous from the patients with active lesions showed IgG versus the specific antigen of T. gondii. In the patients with inactive lesions the pattern was the same in the two compartments. In active forms, aqueous and serum Western blot patterns differed in proteins lower than 16kDa and higher than 116kDa: in aqueous the findings were typically positive for 30kDa.
Conclusions: Aqueous humour analysis by the Western blot technique may be useful in the diagnosis of congenital toxoplasmosis. In the present small series, we nevertheless detected different patterns for inactive and active retinochoroiditis, confirming the diagnosis in the latter. Aqueous humour paracentesis may be indicated in a child with active retinochoroiditis with unusual clinical features, appearing after the first year of life, and with no clinical or serological evidence of congenital infection.