It's particularly common in England. In Paget's disease, both osteoclasts and osteoblasts become overactive in some areas of bone, and the turnover rate in these areas increases tremendously. The overactive areas enlarge but are structurally abnormal and therefore weaker than normal areas. The cause of Paget's disease isn't known. Although the disorder tends to run in families, no specific genetic pattern has been discovered.
Some evidence suggests that a viral infection is involved.
Symptoms Paget's disease usually produces no symptoms. When symptoms such as stiff joints and fatigue occur, they usually develop slowly and subtly. Bone pain, enlargement, or deformity may occur. Bone pain may be deep, aching, and occasionally severe and may worsen at night. The enlarging bones may compress nerves, adding to the pain.