Serum melatonin in juvenile rheumatoid arthritis: correlation with disease activity

The study was conducted to investigate the abnormalities in early morning serum melatonin among patients with Juvenile Rheumatoid Arthritis (JRA) and to outline its relation to disease activity and severity. Twenty one patients with JRA and twenty healthy age and sex matched controls were enrolled in the study. Fifteen patients had polyarticular JRA, 3 had oligoarticular and 3 had systemic onset JRA. Evaluation was carried out clinically, functionally and radiologically by using disease activity score, Juvenile Arthritis Functional Assessment Report for Children (JAFAR-C score) and modified Larsen score, respectively. Laboratory investigations included Complete Blood Picture (CBC), The Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein (CRP), classic IgM Rheumatoid Factor (RF), Anti-nuclear Antibodies (ANA) and melatonin estimation in serum. The serum levels of melatonin were significantly increased in JRA patients (mean +/- SD = 13.9 +/- 8 pg mL(-1)) as compared to healthy controls (mean +/- SD = 8.1 +/- 2.7 pg mL(-1), p < 0.01). A significant positive correlation could link serum melatonin levels to disease activity scores and ESR (r = 0.91, p < 0.001 and r = 0.55, p < 0.01, respectively). No significant correlation was found between melatonin and either Larsen or JAFAR scores (r = 0.19, r = 0.15, respectively). According to melatonin levels, there were 2 groups of patients: Group I with elevated melatonin level (more than 11 pg mL(-1)) (n = 15) and group II with normal melatonin level (less than 11 pg mL(-1)) (n = 6). Patients with elevated melatonin levels had higher ESR (p < 0.05), higher disease activity scores (p < 0.01) and Larsen scores (p < 0.05), than the group of patients with normal serum melatonin. The results of GAFAR scores were comparable between the two groups (p > 0.05). Hence the study conclude that the elevated melatonin levels among JRA patients with active synovitis and its close relation to disease activity rather than disease severity suggests that melatonin might play a promoting role in rheumatoid arthritis. Hence, inhibition of its synthesis and/or action by specific antagonists may be of therapeutic value.