Patients who are scheduled to have orthopedic surgery for treatment of polyostotic fibrous dysplasia may participate in this study. A small sample of bone tissue removed during surgery will be given to investigators in this study for research tests. DNA will be extracted from the tissue and tested for the mutation. Investigators will attempt to grow cells from the sample in the laboratory to evaluate them for their ability to grow and make proteins that normal bone cells make. These tests are designed to help scientists understand how the mutation leads to abnormal bone formation and provide information that might lead to better treatments for fibrous dysplasia. Patients with juvenile Dermatomyositis who have a calcinosis sample surgically removed are also eligible for participation. The removed tissues will be examined for their composition and microscopic appearance, to better understand the pathogenesis of dystrophic calcification in this disease.