Bone disease in systemic sclerosis: outcomes and associations

The relationship between systemic sclerosis (SSc) and low bone mineral density (BMD) is poorly understood. The aim of this study is to improve our understanding of low bone density in SSc and its potential consequences.

Fifty consecutive unselected SSc patients were approached. Demographics, disease manifestations, BMD (lumbar spine and femoral neck) were collected at baseline and occurrence of fracture and death were collected over 2 years. The 10-year risk of osteoporotic fracture was estimated using the fracture risk assessment tool (FRAX) v2.0 with the Canadian population reference. Fisher's Exact and Student's t-tests were used to evaluate differences between patients with and without low BMD. Logistic regression was used for multivariate analysis.

Forty-five patients had complete BMD data. Twenty-eight patients (62%) had low BMD, of those 10 (36%) had osteoporosis. There was no difference in age, sex, or disease duration between both groups. Low BMD was associated with non-Caucasian race (57% vs. 18%, p=0.01), postmenopausal status (83% vs. 47%, p<0.01), low body mass index (24.5 vs. 26.2, p=0.05). The mean 10-year risk of developing a major osteoporotic fracture and a femoral neck fracture was higher in the low BMD group (10.2% vs. 4.8%, p=0.12) and (4.1% vs. 0.5%, p = 0.16) respectively. Fourteen percent (4/28) of SSc patients with low BMD had a fracture, compared to 6% (1/17) SSc patients without low BMD. Fracture-related mortality did not occur in any patients.

Low BMD and fracture are frequently seen in SSc patients. A number of clinically relevant factors are associated with low BMD. Further research is needed to evaluate these factors and the role of bone-specific treatments in SSc.