Paget disease is an abnormality of the growth cycle of bone. Normally, bone breaks down and is rebuilt daily. In Paget disease, the bone cells break down more rapidly and regrow more rapidly than normal. This results in bone that is rebuilt in a more random fashion. As a result, individuals can experience pain, skull enlargement and bowing of the legs. Paget disease is often without symptoms and is the second most common bone disorder in people over age fifty.