Paget disease of bone is a metabolic disorder in which there is an abnormality of bone remodeling. It was first described by Sir James Paget in 1877 with the name osteitis deformans. The condition results from a focal increase in the activity of osteoclasts and osteoblasts. In advanced stages of the disease, this can spread to involve larger parts of the bone. People afflicted with Pagets disease of bone develop enlarged deformities, particularly in weightbearing regions. Susceptibility to the disease is determined by genetic factors.