Association between vitamin D receptor gene polymorphisms and vitamin D supplementation in juvenile idiopathic arthritis: an observational case–control study

Abstract Background Juvenile Idiopathic Arthritis is a term used to describe a wide range of chronic inflammatory diseases, characterized by arthritis of undefined causes persists more than 6 weeks, in children under 16 years old, excluding all other causes of pediatric joint pathologies. The aim of this study was to assess Vitamin D status among Egyptian children with Juvenile Idiopathic Arthritis, and to determine its relationship with vitamin D receptor polymorphisms in Juvenile Idiopathic Arthritis children under treatment. Methodology The study was conducted on 120 Juvenile Idiopathic Arthritis patients and 100 healthy children as controls. The serum levels of serum 25-hydroxyvitamin D were measured in patients and controls by Enzyme Linked Immunosorbent assay, before and after vitamin D supplementation. Single nucleotide polymorphism of vitamin D receptor gene was assessed by real-time polymerase chain reaction in all study subjects. Results Lower 25-hydroxyvitamin D serum levels were found in Juvenile Idiopathic Arthritis children, compared to controls ( p  < 0.001). Moreover, there was a significant difference in serum 25-hydroxyvitamin D concentration in active and non-active Juvenile Idiopathic Arthritis. Vitamin D receptor genetic polymorphisms were the same in patients and controls apart from FokI polymorphism. There was no difference in vitamin D receptor polymorphisms regarding disease activity. The best response to vitamin D supplementation is associated with the FF genotype of the FokI and the tt genotype of the TaqI polymorphisms in patients and controls. Conclusion Vitamin D is suggested to have an important role in autoimmune diseases, and alterations in vitamin D status may be associated with inflammatory processes. In Egyptian Juvenile Idiopathic Arthritis patients; FokI polymorphisms are associated with increased disease prevalence, ApaI polymorphisms are associated with lower 25-hydroxyvitamin D levels, but the relation between vitamin D receptor polymorphisms and the patients’ response to vitamin D supplementation still needs further research.