Paget's disease of bone (also termed ambiguously, just Paget's disease) Paget's is caused by the excessive breakdown and formation of bone, followed by disorganized bone remodeling. This causes affected bone to weaken, resulting in pain, misshapen bones, fractures and arthritis in the joints near the affected bones. Rarely, it can develop into a primary bone cancer known as Paget's sarcoma. Often Paget's disease is localized to only a few bones in the body. The pelvis, femur, and lower lumbar vertebrae are the most commonly affected bones. Paget's disease typically is localized, affecting just one or a few bones, as opposed to osteoporosis, for example, which usually affects all the bones in the body.