Disease Activity, Proteinuria, and Vitamin D Status in Children with Systemic Lupus Erythematosus and Juvenile Dermatomyositis

ObjectiveTo evaluate relationships among vitamin D, proteinuria, and disease activity in pediatric systemic lupus erythematosus (SLE) and juvenile dermatomyositis (JDM).Study designMultiple linear regression was used to associate subject-reported race, sunscreen use, and vitamin D intake with physician-assessed disease activity and serum 25-hydroxyvitamin D (25[OH]D) in 58 subjects with pediatric SLE (n = 37) or JDM (n = 21). Serum 25(OH)D was correlated with urinary vitamin D binding protein/creatinine ratio (DBP/C) and other indicators of proteinuria.ResultsSerum 25(OH)D levels in subjects with SLE were inversely associated with the natural log of urinary DBP/C (r = −0.63, P < .001) and urine protein to creatinine ratio (r = −0.60, P < .001), with an adjusted mean 10.9-ng/mL (95% CI, 5.1-16.8) decrease in 25(OH)D for those with proteinuria. Excluding subjects with proteinuria, serum 25(OH)D levels were inversely associated with disease activity in JDM, but not in SLE. Overall, 66% of all subjects were taking concurrent corticosteroids, but this was not associated with 25(OH)D levels.ConclusionsLow serum 25(OH)D in patients with SLE is associated with proteinuria and urinary DBP. Vitamin D deficiency is associated with disease activity in patients with JDM and SLE; this relationship in SLE may be confounded by proteinuria.