Effects of vitamin D metabolism on clinical findings and etiopathogenesis in patients with juvenile idiopathic arthritis

There are studies suggesting that vitamin D may play role in the etiopathogenesis of juvenile idiopathic arthritis (JIA) and disease activity in children with JIA. To the best of our knowledge, this is the first study investigating amount and expression of VDR in patients with JIA. Forty patients aged 3-18 year old who have been followed with the diagnosis of oligoarticular and polyarticular JIA at Pediatric Rheumatology Unit of Pediatric Nephrology Department of Akdeniz University, Medicine School were included in the study. Sixteen age- and sex-matched children who were diagnosed as primary monosymptomatic nocturnal enuresis at Pediatric Nephrology outpatient clinic but had no history of other disease were employed as control group. The study was conducted between June, 2013 and August, 2013. In the patient and control groups, complete blood count, CRP, ESR, calcium, phosphor, PTH, and calcitonin values, vitamin 25(OH)D3 and 1,25(OH)2D3 levels, amount of vitamin D receptors and VDR expression percentages in CD4+, CD8+, CD56+ lymphocytes and CD14+ monocytes were assessed. There were 28 girls (70%) and 12 boys (30%) in the patient group while 10 girls (62.5%) and 6 boys (37.5%) in the control group. Mean age was 10.46±4.63 years in the patient group and 8.59±3.11 years in the control group. In the patient group, we detected vitamin D deficiency (≤15 ng/ml) in 23 patients (57.5%), vitamin D insufficiency (15-20 ng/ml) in 9 patients (22.5%) and sufficient vitamin D levels in 8 patients (20.0%). In the control group, we detected vitamin D deficiency in 7 patients (43.7%), vitamin D insufficiency in 4 patients (25.0%) and sufficient vitamin D levels in 5 patients (%31.2). Mean vitamin 25(OH)D3 and 1,25(OH)2D3 levels were significantly higher in the control group compared to the patient group, but the difference didn't reach statistical significance. Amount of VDR in CD8+ lymphocytes was found to be significantly lower in the patient group (p=0.042). No significant differences were detected in the percent of CD4+, CD8+, CD56+ lymphocytes and CD14+ monocytes expressing VDR between the patient and control groups. In the patient group, amount of VDR in CD4+, CD8+ and CD56+ lymphocytes was found to be significantly higher in patients receiving corticosteroid compared to those not receiving (p=0.010) (p=0.017) (p=0.023). A significant, moderate, positive correlation was found between cumulative steroid dose and CD14+ monocyte expressing VDR (r=0.553; p=0.011). In our study, disease activity was calculated by using JADAS-27 scoring system. No significant correlation was detected between JADAS-27 score and vitamin 25(OH)D3 and 1,25(OH)2D3 levels, amount of VDR in CD4+, CD8+, CD56+ lymphocytes and CD14+ monocytes or VDR expression percentage. Our results suggest that vitamin D and VDR may have influence on JIA. Further studies are needed in this topic.