Paget's disease of bone (commonly known as Paget's disease or, historically, osteitis deformans) is a condition involving cellular remodeling and deformity of one or more bones. The affected bones show signs of dysregulated bone remodeling at the microscopic level, specifically excessive bone breakdown and subsequent disorganized new bone formation. These structural changes cause the bone to weaken, which may result in deformity, pain, fracture or arthritis of associated joints.
The exact cause is unknown, although leading theories indicate both genetic and acquired factors (see Causes). Paget's disease may affect any one or several bones of the body (most commonly pelvis, tibia, femur, lumbar vertebrae, and skull), but never the entire skeleton, and does not spread from bone to bone. Rarely, a bone affected by Paget's disease can transform into a malignant bone cancer.
