Paget’s Disease of Bone

The Surgeon General says it is estimated that one million Americans have Paget’s disease.

Paget’s disease of bone is named after the orthopedic surgeon who first described the condition. It is a chronic disease of the skeleton, occurring in about three percent to four percent of the population age 50 and over and only rarely in people younger than 40 years old. It is a little more common in men than women. It is also more common in England, the United States, Australia, New Zealand, and Western Europe and in people of people of Anglo-Saxon descent. It is not common in Scandinavia, Japan, China, or India. But these incidence differences may be due to different requirements for reporting the condition.

Paget's disease tends to appear in families. In 2009, scientists reported that four genes are associated with the condition. The exact action of these genes remains unknown. Some scientists suggest that an environmental exposure, in addition to genetics, is important in the development of Paget's disease. There are no known ways to prevent Paget's disease.

Cause

In healthy bone, some cells (osteoclasts), are constantly absorbing bone while others (osteoblasts) are constantly depositing new minerals. Bone is constantly turning over in this process called remolding. In Paget's disease, the process is not regulated properly. First, osteoclasts begin to absorb bone too quickly. In response, osteoblasts deposit excess mineral in the bone. Bones affected by Paget’s disease are abnormally large and deformed. The excess mineral is not deposited in the typical three-dimensional structure that gives bone strength. So the bone is also brittle and susceptible to fracture.

Symptoms

Some people with Paget's disease have no symptoms at all. An X-ray taken for another reason may reveal abnormal bone; a routine blood test may reveal clues to unusual bone metabolism. In patients with symptoms, bone pain is the most frequent complaint. The pain is caused by fractures, arthritis in the joints near affected bone, or compression of nerves by enlarged and misshapen bones.

Paget's disease may develop into a bone cancer called Paget's sarcoma. This occurs in less than one percent of patients diagnosed with Paget’s disease and usually only in patients older than 70.

Diagnosis

A doctor can usually diagnose Paget's disease by looking at an X-ray. A simple blood test for alkaline phosphatase is also be used to confirm the diagnosis. This test measures bone turnover. This enzyme is usually clearly elevated in patients with Paget's disease. Paget's disease is also detected with a urine test.

A doctor may order a bone scan nuclear imaging test to determine if more than one bone is involved. Before the scan, a radioactive material is administered intravenously. A special camera visualizes the whole skeleton for areas where there is more bone turnover than usual. A bone biopsy is sometimes performed to rule out other diagnoses and to confirm the diagnosis of Paget's disease.

Treatment of Paget’s Disease

There is no known way to cure Paget’s disease or reverse its effects on bones. Treatment emphasizes relieving symptoms. Patients who have mild pain from the disease or from arthritis associated with it are recommended nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin. When the legs are affected, use of a cane may decrease the pain of walking and to help prevent falls. If bone pain is severe, bisphosphonate drugs are used to regulate the bone remolding process.

If there is a fracture, surgery may be required. Badly aligned bones and those damaged by arthritis may be surgically treated. Surgery may also be needed if an enlarged bone begins to compress spinal nerves or the brain. In the rare case of Paget's sarcoma, tumors are removed surgically often followed by chemotherapy and radiation therapy.

Scientists are currently investigating the genes associated with Paget’s disease. Understanding their function may lead to new treatments to stop and repair bone damage due to Paget’s disease.