Paget's Disease of Bone

What Is It?

Bones in your body continuously break down and form again in a natural and tightly balanced process called bone remodeling. This bone remodeling also occurs in response to stress or injury placed on the bone. For example, weight-bearing exercise leads to increased bone formation.

In Paget's disease, more bone breaks down than usual and more new bone forms than usual. These changes in the bone can lead to bone enlargement and deformity. The new bone growth tends to be softer and more fragile than normal bone, and can develop in a haphazard pattern. Because of this, the bone can fracture. The long bones, especially the legs, tend to bow, and the skull may enlarge, particularly over the forehead.

Paget's disease is the second most common bone disorder in people over 50, after osteoporosis. It is rarely diagnosed in young adults.

Although the cause is unknown, genetics may play a role because the disease seems to run in families. Research suggests a slow-growing virus may trigger the disease; some cells in the bone of people with Paget's disease look like they are infected with a virus. However, no virus has been identified.

The condition is rare in certain parts of the world, such as Japan, but more common in the United States and Australia. In the United States, an estimated 10 percent of people older than 80 have Paget's disease.

In about 20 percent of people with Paget's disease, only one area of the body — the spine, pelvis, thighs, lower legs or skull — is affected. The rest have many areas involved. In serious cases, complications can include deafness, congestive heart failure (caused by the extra blood flow required by the diseased bone), an elevated calcium level and cancer of the bone.

Symptoms

An estimated 70 percent of people with Paget's disease do not have any symptoms. Symptoms are more likely to occur in people who have many areas of the body affected. Symptoms can include:

• Bone pain and warmth
• Headache
• Head enlargement
• Bowing of the legs
• Hearing loss
• Weakness or constipation (due to elevated blood calcium levels, a complication of increased bone remodeling)

Diagnosis

Because many people with Paget's disease do not have symptoms, the condition often is not discovered until an X-ray or blood test taken for another reason suggests the disease may be present. If your doctor thinks you may have Paget's disease, specific blood and urine tests can measure the levels of certain byproducts of bone formation and breakdown. More detailed X-rays or a bone scan also may be done. In rare instances, a doctor may recommend a bone biopsy to confirm the diagnosis and exclude other possibilities. In a bone biopsy, a small piece of bone is removed with a needle so it can be examined in a laboratory.