Elevated S100A8/A9 and S100A12 Serum Levels Reflect Intraocular Inflammation in Juvenile Idiopathic Arthritis-Associated Uveitis: Results From a Pilot Study

Juvenile idiopathic arthritis-associated uveitis (JIAU) is the most common uveitis entity in childhood. As S100A8/A9 and S100A12 proteins are valuable biomarkers in childhood arthritis, we investigated the occurrence of these proteins in childhood uveitis. Serum samples from patients with JIAU (n = 79) or idiopathic anterior uveitis (IAU, n = 24), as well as from nonuveitic controls (n = 24), were collected. Furthermore, aqueous humor samples (JIAU n = 17, nonuveitic controls n = 16, IAU n = 12) were obtained. Samples were analyzed for S100A8/A9 and S100A12 protein levels by ELISA. Intergroup comparisons were performed, involving patient data, clinical data, and S100 levels. S100A8/A9 and S100A12 serum levels were elevated in IAU and JIAU patients as compared to nonuveitic controls (all P < 0.05). S100 serum levels in JIAU patients were higher in active arthritis (not significant; P = 0.289 for S100A8/A9 and P = 0.196 for S100A12) and active uveitis (P = 0.010 for S100A8/A9 and P = 0.026 for S100A12) than in controls. No significant differences in S100 levels were found in a subgroup analysis for sex, antinuclear antibody (ANA) status, disease duration, or presence of uveitis complications. In JIAU patients, S100 serum levels correlated with age and age at onset of uveitis. A longitudinal analysis in JIAU patients showed a correlation of serum S100A8/A9 and S100A12 levels with uveitis activity (both P = 0.03). S100A8/A9 levels in aqueous humor of patients with JIAU (P = 0.001) and IAU (P = 0.0002) were increased as compared to nonuveitic controls. Increased S100A8/A9 and S100A12 levels are found in the serum and aqueous humor of patients with autoimmune uveitis. Serum levels reflect activity of joint and eye disease.