This increased risk of fracture is due partly to an increased risk of falling, and secondly to an impairment of bone tissue with lower bone mineral density (BMD). A meta-analysis concluded that patients with IPD have lower BMD than healthy controls. Prospective studies also showed rapid bone loss in these patients compared with controls. The association between low BMD and IPD seems dependent on the severity and duration of the disease even if some data are contradictory. Various mechanisms may explain this bone loss including weight loss, malnutrition and a low level of physical activity. However, enrollments in these studies are often weak and it is difficult to conclude on the real impact of these factors on bone loss in the IPD. The main objective of our study is to assess and prioritize from these various bone loss mechanisms. Bone assessment by "peripheral quantitative computed tomography" (pQCT) will also assess the impact of various risk factors on bone strength parameters. The prevalence of vertebral compression fractures in the IPD, at this day unknown can be evaluated. This study will also estimate the prevalence of vertebral compression fractures in the IPD.