Recurrent toxoplasmic retinochoroiditis: a study of 58 cases with initial aqueous humor analysis

Abstract

Purpose: To analyze recurrence patterns of toxoplasmic retinochoroiditis in a series of cases with initial analysis of aqueous humor, and to investigate the relation between recurrences, clinical and biological factors.

Methods: Consecutive patients who presented a clinical diagnosis of toxoplasmic retinochoroiditis and a concordant positive aqueous humor analysis between January 2005 and December 2008 were retrospectively included. Aqueous humor analysis was positive if it fulfilled at least one criteria among: Goldmann-Witmer coefficient > 2, positive Toxoplasma gondii PCR or > 1 additional or more intense band on immunoblotting. HIV-infected patients were excluded.

Results: 58 consecutive patients were included. Mean age at first manifestation was 39 years, and mean follow-up was 7 years. 23 patients had recurrences, with a mean number of 1.6 recurrences per patient. Distribution of time intervals showed that a significant number of episodes occurred by clusters, defined as two episodes occurring within 15 months (p=0.0003, Kolmogorov-Smirnov test). Survival analysis in a subgroup of patients with early first recurrences, defined by a recurrence within 15 months following the first episode, showed a reduction in the number of subsequent episodes compared to those with delayed first recurrences (p=0.02, Log Rank test). Arterial vasculitis was more frequent in the group with early first recurrences (p=0.009, Fisher's exact test), which highlights the critical role of the blood-aqueous barrier in the host response to parasite invasion.

Conclusions: Toxoplasmic retinochoroiditis recurrences are not random events. Their occurrence depends on several host and parasite factors. Aqueous humor samples used for diagnosis confirmation in severe cases are also helpful to improve our understanding of these processes.

Keywords: 734 toxoplasmosis • 553 immune tolerance/privilege • 451 chorioretinitis