Background Besides the genetic background, it is known that environmental factors play an important role in the pathogenesis and activity of autoimmune diseases and vitamin D deficiency has been associated with the risk and severity of autoimmune diseases. Apart from traditional calcium-related actions, vitamin D is now being recognized for its role in immune-homeostasis, affecting both innate and adaptative immune systems and contributing to immune-tolerance of self-structures.
Objectives To compare the vitamin D serum levels in systemic sclerosis (SSc) patients with healthy controls and to explore the predictors of vitamin D serum levels in SSc patients and the association between its levels with clinical and biological aspects.
Methods The levels of 25-hidroxyvitamin D (25OHD) were determined in a cohort of 45 SSc patients and in 27 healthy controls gender-, age- and season-matched, not taking vitamin D supplements.
The SSc patients underwent a complete clinical and laboratorial evaluation, which included sun exposure time, 25OHD serum level and modified Rodnan skin score. Sun exposure time was estimated using a semi-quantitative scale. 25OHD levels were classified as deficient (<10ng/ml), insufficient (≥10ng/ml and <30ng/ml) and normal (≥30ng/ml).
Data was analyzed using the SPSS® version 19.0 for windows. Categorical data is presented as proportions/percentages and continuous variable as median and inter-quartile range. Comparisons across groups were performed using non-parametric tests. P<0,05 is considered statistically significant.
Results The mean age was 59.4+11.5 years and 53.7+11.5 years for SSc patients and controls respectively. Females represented 87.7% of the SSc group and 85.2% of the control group.
We registered a statistically significant difference in 25OHD levels between SSc group and control group (Z=-4,392, p<0,001, median 16,3ng/ml versus 27ng/ml).
Estimated sun exposure time was smaller in SSc patients than in controls. The difference in 25OHD levels between groups remained statistically significant even after adjusting 25OHD levels for sun exposure time. In logistic regression analysis both the disease (β=0,329, p=0,001) and sun exposure time (β=0,483, p<0,001) were considered predictors of 25OHD levels.
The mean level of 25OHD among SSc patients was 16,6±8,3 ng/ml and suboptimal levels of 25OHD were observed in 40 patients (88,9%). 25OHD serum levels were lower in patients with shorter sun exposure time (χ2=2,32, p<0,001). A significant negative correlation was observed between 25OHD serum levels and Rodnan skin score (rs=-0,458, p=0,002). Significant correlation was not found between 25OHD serum concentrations and other clinical or biological aspects.
Conclusions Patients with SSc have significantly lower median serum vitamin D concentrations than healthy control subjects, and a higher prevalence of vitamin D deficiency. Both disease and sun exposure time are considered good predictor of vitamin D values.
Lower levels of vitamin D are observed in patients with shorter sun exposure time and a negative correlation was observed between vitamin D levels and skin involvement.
Caramaschi P, Dalla Gassa A, Ruzzenente O, Volpe A, Ravagnani V, Tinazzi I, Barausse G, Bambara LM, Biasi D. Very low levels of vitamin D in systemic sclerosis patients. Clin Rheumatol. 2010 Dec;29(12):1419-25.
Disclosure of Interest None Declared
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