Serum 25-OH vitamin D level in treatment-naïve systemic lupus erythematosus patients: Relation to disease activity, IL-23 and IL-17.

Objectives The aim of this study was to assess the vitamin D status in treatment-naïve SLE patients and its association with clinical and laboratory markers of disease activity, including serum levels of IL-17 and IL-23. Methods Fifty-seven treatment-naïve SLE patients along with 42 matched controls were included. SLEDAI score was used to estimate disease activity. Serum levels of 25(OH) D, IL-17 and IL-23 were measured. Results The median level of 25(OH) D in SLE patients (40.8; 4-70 ng/ml) was significantly lower than in the controls (47; 25-93 ng/ml) ( P = 0.001). A total of 38.6% of SLE cases had 25 (OH) D levels < 30 ng/ml (hypovitaminosis D) vs. 4.8% of the controls ( P < 0.0001). Apart from thrombocytopenia, vitamin D was not associated with clinical signs of SLE. There were negative correlations between serum 25(OH) D and serum levels of IL-17, IL-23 and ANA (rho = -0.5, -0.8, -0.5, P ≤ 0.05) in SLE patients. Conclusion Hypovitaminosis D is prevalent in treatment naïve SLE patients. It contributes to ANA antibody production and is associated with high serum levels of IL-23 and IL-17; thus they may trigger the inflammatory process in SLE.