Introduction: Hypovitaminosis D has been frequently described in systemic sclerosis (SSc). Cytokines are important mediators of tissue damage and clinical dysfunction in SSc and may be influenced by vitamin D levels.
Objective: To evaluate the serum levels of vitamin D and its correlation with the clinical features and cytokine profiles in SSc patients.
Methods: Case-control study, including 50 SSc patients and 35 healthy non matched controls. Serum levels of 25(OH) vitamin D were measured by chemiluminescence assay, and serum concentrations of interleukin 2 (IL-2), IL-4, IL-6, IL-10, tumor necrosis factor, and interferon γ were determined by flow cytometry.
Results: Fourteen patients (28%) had diffuse cutaneous SSc, 94% were female, 80% European derived, with a mean age of 57.2 ± 12.8 years. The serum vitamin D levels in SSc patients were 23.9 ± 8.5 ng/mL and 30.2 ± 6.2 ng/mL in the control group (standardized mean difference -6.19; 95% confidence interval, -9.9 to -2.3; p = 0.002), despite the more frequent supplementation of vitamin D in SSc patients (p = 0.014). No significant associations were found among vitamin D concentrations and cytokine levels. Serum levels of IL-6 were significantly elevated in SSc patients (p = 0.024) and were positively correlated with the modified Rodnan skin score (rs = 0.291, p =0.041).
Conclusions: Despite lower vitamin D levels in SSc patients, there was no clear association with any cytokine. Serum levels of IL-6 were significantly elevated and positively correlated with the extent of skin involvement in SSc patients.