Paget's disease of bone (also termed osteitis deformans or, ambiguously, just Paget's disease; "Paget" is pronounced ) is a chronic disorder that can result in enlarged and misshapen bones. 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. The disease is named after Sir James Paget.