Objectives: Disproportionate vitamin D levels may play an important role in the development of certain systemic autoimmune and rheumatic diseases. The aim of the present study was to investigate the prevalence of vitamin D insufficiency in patients with systemic lupus erythematosus (SLE) and to compare serological and clinical parameters in patients with different vitamin D levels from a single centre registry in Central-Eastern Europe.
Methods: A total of 177 patients with SLE were enrolled in the study. 25-Hydroxyvitamin D [25(OH)D] levels were measured by chemiluminescent immunoassay (CLIA). Autoantibody profiles, complement 3 (C3) and C4, clinical symptoms, and disease activity (using the SLE disease activity index, SLEDAI) of the patients were assessed.
Results: Vitamin D concentration in the total SLE group investigated was 26.88 ± 13.25 ng/mL. Vitamin D levels were normal (≥ 30 ng/mL) in 18.1% of patients, insufficient (15-30 ng/mL) in 44.6%, and deficient (< 15 ng/mL) in 37.3%. The vitamin levels were significantly reduced in postmenopausal compared to premenopausal patients (p = 0.02). Patients with pericarditis (p = 0.013), neuropsychiatric diseases (p = 0.01), and deep vein thrombosis (p = 0.014) had reduced vitamin D levels. SLEDAI score was significantly increased in patients with reduced vitamin D levels (p = 0.038). Anti-double-stranded (ds)DNA autoantibody concentrations increased from normal to insufficient and further increased from insufficient to deficient patient subsets (p = 0.021). Anti-Smith antigen (anti-Sm) concentrations increased (p < 0.001), C4 levels decreased (p = 0.027), and immunoglobulin (Ig)G concentration increased (p = 0.034) in patients with reduced vitamin D levels.
Conclusions: Our data suggest that vitamin D deficiency in SLE may play a role in perpetuation of the disease.