The objective was to evaluate the 25(OH) vitamin D (25(OH)D) status of patients with juvenile idiopathic arthritis (JIA) and determine whether the 25(OH)D level is associated with disease activity and the course of JIA.
Patients ≤ 16 years of age with recently diagnosed JIA (< 12 months) were enrolled in the inception cohort of patients with newly diagnosed JIA (ICON), an ongoing prospective observational, controlled multicenter study started in 2010. Clinical and laboratory parameters were ascertained quarterly during the first year and half-yearly thereafter. Of the 954 enrolled patients, 360 patients with two blood samples taken during the first 2 years after inclusion and with follow up of 3 years were selected. The serum 25(OH)D levels were determined and compared with those of subjects from the general population after matching for age, sex, migration status and the month of blood-drawing.
Nearly half of the patients had a deficient 25(OH)D level (< 20 ng/ml) in the first serum sample and a quarter had a deficient level in both samples. Disease activity and the risk of developing JIA-associated uveitis were inversely correlated with the 25(OH)D level (β = - 0.20, 95% CI - 0.37; 0.03, hazard ratio 0.95, 95% CI 0.91; 0.99, respectively).
In this study, 25(OH)D deficiency was common and associated with higher disease activity and risk of developing JIA-associated uveitis. Further studies are needed to substantiate these results and determine whether correcting 25(OH)D deficiency is beneficial in JIA.