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 younger people. 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. An Englishman, Sir John Paget, first described the disease in 1876.
Paget's disease tends to run 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. It has been suggested that the measles virus plays a part, and indeed incidence of Paget’s disease has declined since introduction of the measles vaccine.
In healthy bone, some cells (osteoclasts), are constantly breaking down bone mineral material while others (osteoblasts) are constantly depositing new minerals. Bone is constantly turning over in this process called remodeling. 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.
Most people with Paget's disease have no external signs. An X-ray taken for another reason may reveal abnormal bone, or a blood test may reveal clues to unusual bone metabolism. 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.
A doctor can usually diagnose Paget's disease by looking at an X-ray. A simple blood test for alkaline phosphatase is also used to confirm the diagnosis. This test measures bone turnover. This enzyme is usually clearly elevated in patients with Paget's disease. Urine tests are also employed.
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. The imaging machine examines the 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.
The bisphosphonate zoledronate is the “treatment of choice” https://www.ncbi.nlm.nih.gov/books/NBK279033/. 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 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 and chemotherapy and radiation therapy may be employed.
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.