What Happens

In healthy people, bone is constantly being replaced as bone tissue is broken down and absorbed into the body, then rebuilt with new cells. In the early stages of Paget's disease, bone tissue breaks down faster than it rebuilds. To make up for this breakdown process, the body speeds up the rebuilding process. But this new bone is often weak and brittle, causing it to break (fracture) more easily. Your body also tends to produce too much of this new bone, and the bone may have more blood supply than normal.

Paget's disease usually affects the bones in the pelvis, spine, thigh (femur), skull, shin (tibia), and upper arm (humerus). Paget's disease may affect just one bone (monostotic), but it usually affects more than one (polyostotic).

Early in Paget's disease, you may not know that you have it. People often mistake symptoms such as bone pain for normal aging or osteoarthritis. Later in the disease, you may have signs such as bowed legs, enlarged skull or facial bones, stooped-forward posture, or broken bones (fractures).

Paget's disease is a lifelong illness and can be either active or inactive at different times. Paget's disease rarely spreads to additional bones after it gets started. Most people who have Paget's disease lead normal lives.

Complications of Paget's disease are rare but may include inflammation of joints (arthritis), broken bones (fractures), heart failure, and nerve problems. Nerve problems can cause a variety of symptoms, such as headache, dizziness, hearing loss, and vision problems.