Vitamin D receptor Bsm1 polymorphism, calcium metabolism and bone mineral density in patients with multiple sclerosis: a pilot study

Vitamin D receptor's (VDR) genotypes have been associated both with the development of bone disease and the pathogenesis of multiple sclerosis (MS). We aimed to evaluate the association between the presence of Bsm1 restriction fragment length polymorphism of VDR and bone loss in ambulatory patients with MS. This cross-sectional study included 82 adult patients with relapsing-remitting MS. Fasting blood samples were obtained for biochemical-hormonal assessment and genotyping. Bone mineral density (BMD) was assessed at the lumbar spine (LS) and the femoral neck (FN), using dual energy X-ray absorptiometry. Possible associations between VDR's genotypes and BMD levels as well as biochemical and hormonal indices were evaluated. Among premenopausal women and men, carriers of the B allele exhibited higher BMD and Z score at the FN and a trend toward higher BMD at the LS, compared to patients with the bb genotype, after adjusting for age, BMI, sex, EDSS scoring, interferon administration, duration of MS and total steroids intake. Among postmenopausal women, the presence of the B allele was not associated with BMD or T score at any site, whereas carriers of the B allele exhibited higher levels of calcium (p value 0.008, univariate). No other significant differences were exhibited between levels of electrolytes, parathormone, 25-hydroxyvitamin D-3 and the genotype of VDR, in any of the groups. VDR's Bsm1 polymorphism is associated with a mild effect on BMD in younger patients with MS. Larger studies are necessary to corroborate these findings.