Low serum vitamin D concentrations in systemic sclerosis patients from two European centers: Clinical correlations and treatment perspectives

Background: Immune responses are influenced by vitamin D (25(OH)D) in physiology and pathology. Systemic sclerosis (SSc) patients show low 25(OH)D serum concentrations. Objective: To evaluate in SSc, correlations between 25(OH)D serum concentrations and clinical parameters, seasonality and effects of standard oral supplementation. Methods: 154 SSc patients (131 females and 21 males, age 59 ± 15 years, diffuse 24.7% form and limited form 75.3%) were enrolled, at any time of the year. LIAISON 25-OH vitamin D assay (Diasorin, Italy) was used (< 20 ng/mL = deficiency, 20- 30 ng/mL = insufficiency). Pulmonary function test, chest xray, lung CT scan, electrocardiography, Doppler echocardiography, renal artery resistive index by eco color Doppler, Dual Xray absorptiometry, nailfold videocapillaroscopy (NVC), Medsger disease severity scale (DSS), were performed at the time of sample collection. Drug assumption was recorded. Non-parametric tests were used for statistical analysis. Results: Average 25(OH)D serum concentrations were 18.7 ± 9 ng/mL. A significant difference in 25(OH)D concentrations was observed among seasons (winter: 14.6 ± 7.8 ng/ mL, spring: 17.2 ± 7.9 ng/mL, summer 21.43 ± 10 ng/mL, autumn 20.2 ± 10; P = 0.032). A significant correlation was found between 25(OH)D serum concentrations and presence/ absence of bi-basal fibrotic changes at lung CT scan (16.1 ± 8 ng/mL and 20 ± 10 ng/mL respectively, P = 0.04). Peripheral vascular (P = 0.03), kidney (P = 0 . 02), gastrointestinal (P = 0.05) DSS parameters correlated with serum 25(OH) D. No correlation was observed with digital ulcers incidence, strictly related to patterns of microangiopathy observed at NVC (P < 0.0001). Interestingly, no influence of treatment with vitamin D analogues (1,000 UI daily) was found: 18.8 ± 10 ng/mL in treated and 18.7 ± 9 ng/mL in not treated patients (P = 0.81). Conclusion: Low serum 25(OH)D concentrations characterize SSc patients, not influenced by treatment. Correlations with lung involvement, peripheral vascular, kidney and gastrointestinal DSS parameters and seasonality are evident. Therefore, supraphysiological oral vitamin D3 doses or programmed UVB light exposure should be considered in SSc.