Bone Abstracts

Introduction: Hypovitaminosis D is observed in several rheumatic autoimmune diseases, including systemic sclerosis (SSc); nevertheless, data concerning the possible determinants of reduced serum vitamin D levels in this disease are not fully investigated. The aim of this study is to evaluate the relationship between BMD, body mass composition, skin sclerosis, and serum vitamin D levels in two subsets of SSc patients.

Patients and methods: 55 Post-menopausal SSc patients, classified according to Leroy as limited cutaneous (lSSc) or diffuse cutaneous (dSSc) SSc, were studied. Clinical parameters were evaluated, including the extent of skin involvement (Rodnan skin score). Bone mass density (BMD) at spine and hip, and body mass composition were determined by dual-energy X-ray absorptiometry. Serum calcium, phosphorus, alkaline phosphatase, osteocalcin, urine pyridinium cross-links, intact parathyroid hormone (PTH), and 25-hydroxyvitamin D (25 OHD) were also measured. The study protocol was approved by Local Ethical Committee

Results: In dSSs, BMI, and BMD (spine, femoral neck, and total hip) were significantly lower compared to lSSs (P<0.05). Total body mass was significantly lower in dSSc (P<0.05), with no differences in both fat and lean mass in the two study groups; conversely, body mineral content (BMC) was significantly reduced in dSSc patients (P<0.05). In both groups, hypovitaminosis D was observed (mean 25OHD 16.8±9.7), but 25OHD serum levels were significantly lower in dSSc (P<0.01) and inversely correlated with the extent of skin thickness (r=−0.46, P<0.05). No differences between lSSc and dSSc in serum calcium, phosphorus, alkaline phosphatase, osteocalcin, urine pyridinium cross-links and PTH were found.

Conclusions: These results support the hypothesis that the extent of skin involvement in SSc patients could be an important factor in determining low circulating levels of 25OHD, which in turn could play a significant role in the reduction of BMD and BMC.