25-hydroxyvitamin D3 Levels and Their Clinical Associations in a Polish Cohort of Systemic Sclerosis Patients: A Cross-Sectional Study

Abstract

Vitamin D exhibits immunomodulatory effects in autoimmune diseases. We aimed to evaluate the associations of vitamin D levels with clinical and laboratory features of systemic sclerosis (SSc) in a Polish cohort. The study was prospective in design. SSc patients who met ACR-EULAR 2013 criteria underwent comprehensive clinical and laboratory investigations using the European Scleroderma Trials and Research group (EUSTAR) methodology. We assessed patients’ sera for 25(OH)D3 using a radioimmunoassay, and the cutoff value for vitamin D deficiency was set at 20 ng/mL. Statistical analyses were performed using the Mann–Whitney U test, the Fisher’s exact, and the Spearman’s rho, where appropriate, with a significance threshold set at 0.05. We recruited 68 SSc patients (85% female). The mean 25(OH)D3 level was 21.6 ± 10 ng/mL, and 50% of subjects (n = 34) presented vitamin D deficiency (mean 13.7 ± 3.9 ng/mL). Vitamin D-deficient SSc patients exhibited higher prevalence of arterial hypertension (p = 0.002), proteinuria (p = 0.002), and lung fibrosis (p = 0.032), as well as higher CRP (p = 0.035). The modified Rodnan skin score correlated negatively with 25(OH)D3 in diffuse cutaneous SSc (dcSSc). We found no correlation with the disease duration, age, joints, and the heart. Vitamin D deficiency was common in the studied population of Polish SSc patients and was associated with arterial hypertension, proteinuria, lung involvement, and increased CRP.