Paget’s disease of bone is a chronic disease of the skeleton. In healthy bone, a process called remodeling removes old pieces of bone and replaces them with new, fresh bone. Paget’s disease causes this process to shift out of balance, resulting in new bone that is abnormally shaped, weak, and brittle.
Many patients with Paget’s disease have no symptoms at all and are unaware they have the disease until X-rays are taken for some other reason. When bone pain and other symptoms are present, they can be related to the disease itself or to complications that arise from the disease — such as arthritis, bone deformity, and fractures.
In most cases, treatment for Paget’s disease involves taking medications to help slow or stop the progress of the disease. For patients who have complications, surgery may be needed to realign deformed bones or to help fractures heal.
In normal bone, a process called remodeling takes place every day. Bone is absorbed and then reformed in response to the normal stresses on the skeleton. More specifically:
Cells of the bone called osteoclasts absorb bone.
Cells of the bone called osteoblasts make new bone.
In Paget’s disease, osteoclasts are more active than osteoblasts. This means that there is more bone absorption than normal. The osteoblasts try to keep up by making new bone, but they overreact and make excess bone that is abnormally large, deformed, and fits together haphazardly.
The cause of Paget’s disease is not known, but doctors have identified a number of risk factors that make someone more likely to develop the disease. These include:
- Genetics: Paget’s disease tends to run in families. In as many as 25 to 40% of cases, another relative will also have the disease.
- Age: Paget’s disease occurs only rarely in people under the age of 40. It is more common as people age.
- Environmental factors: Some studies suggest that certain environmental exposures may play a role in the development of Paget’s disease. This has not been proven definitively, however.
Many people with Paget’s disease do not have any symptoms at all. The disease is often first discovered when X-rays are taken for another reason or when routine blood work indicates an elevated blood serum alkaline phosphatase level.
In patients who do have symptoms, bone pain is the most common complaint. This pain can be related to active Paget’s disease or to its complications, which include:
- Fractures due to brittle bone.
- Deformity of bone, including bowing of the affected bone.
- Advanced arthritis in joints near the affected bone.
- Compression on neighboring nerves from enlarged bones, leading to a loss of sensation or movement.