Paget’s disease is the second most common metabolic bone disease after osteoporosis. Approximately 1% of people in the UK, over the age of 55 years, are thought to be affected. The condition is also common in other European countries such as France, Spain and Italy and in people of European descent who have emigrated to other regions of the world, such as Australia, New Zealand, the United States of America and Canada.

Paget’s disease is a metabolic bone disorder in which the normal repair and renewal process within bone is disrupted. Bone affected by Paget's disease is renewed and repaired at an increased rate, causing abnormalities in the bone’s structure. Pagetic bone can appear enlarged and misshapen. Paget’s disease often causes no symptoms and may be found by chance. For those with symptoms, these may include pain, deformity and fracture. Either single or multiple bones may be affected with common sites being the spine, skull, pelvis and thigh (femur).