CONDITIONS AND TREATMENTS

Paget’s Disease of Bone

Paget's disease of bone is a chronic disease of the skeleton. It appears most often in the spine, pelvis, skull, and long bones of the limbs. It can be present in just one bone or in several bones. It can affect the entire bone or just part of it.

It is a common disease in older people, occurring in 3-4 percent of the population over age 50. It is slightly more common in men, than women.

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.

  • Osteoclasts are the cells of the bone that absorb bone.
  • Osteoblasts are the cells of the bone that make new bone.

In Paget's disease, osteoclasts are more active than osteoblasts, so 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 very chaotic. The new bone is abnormally large, deformed, and fits together haphazardly. Normal bone has a tight, overlapping structure like a well-constructed brick wall. Bone afflicted by Paget's disease has an irregular mosaic pattern, as though the bricks were just dumped in place. The end result is bones that are large and dense, but weak and brittle. The bone is prone to fractures, bowing and deformities.

Insert first three black & white images from https://health.uconn.edu/msi/clinical-services/orthopaedic-surgery/bone-tumors-and-oncology/pagets/. See figures 3, 4, 5.

 

Image Image Image
Paget's disease of the spine. The white, patchy appearance of the bone is characteristic of the dense, but disordered bone in this disease. Paget's disease of the pelvis. The bone is thick, wide, and patchy. Paget's disease of the humerus. The bone is dense, wide, and patchy where active bone is turning over.

Symptoms

People with Paget's disease often experience no symptoms at all. A doctor may notice Paget's disease on an X-ray that is taken for another reason or during routine blood work when an elevated serum alkaline phosphatase level is found. For patients who do have symptoms, bone pain is the most common complaint. This pain can be related to active Paget's disease or its complications which include:

  • Fractures of brittle bone
  • Deformity of bone
  • Advanced arthritis of joints near affected bone
  • Loss of sensation or movement caused by compression of nerves near enlarged bones

Fatigue, weakness, loss of appetite, abdominal pain, and constipation are symptoms of a rare complication where elevated calcium levels are found in the blood stream. This occurs when Paget’s disease is active in several bones and overactive osteoclasts release calcium from the bone that makes its way into the blood.

When pain is severe and unrelenting in an area affected by Paget's disease, the disease may have degenerated into bone cancer. Paget's sarcoma occurs in only about 1 percent of patients with Paget's disease. These patients are usually older than 70 years of age. This type of malignant bone tumor is very aggressive and carries a poor prognosis. None of the medical treatments for Paget's disease have had an effect on the risk for the development of Paget's sarcoma.

Diagnosis

Your doctor can usually diagnose Paget's disease by looking at an X-ray. Affected bone appears larger and more dense than usual. It can also have a deformed shape. In the very early stages of Paget's disease, when there is just overactive absorption going on, it can look like there is a hole in the bone. Later in the disease process, this darker area can take the shape of a V, with denser, thicker bone following behind it.

Your doctor may use bone scans to determine if more than one bone is involved. In this test, a radioactive material is injected into your vein to travel throughout the body. A special camera is then used to look for "hot spots" where there is more bone turnover than usual.

A biopsy of the bone is sometimes necessary to confirm the diagnosis of Paget's disease. These biopsies are done with a needle or performed in the operating room through small incisions.

A blood test called serum alkaline phosphatase and urine tests can also be used to confirm the diagnosis of Paget’s disease.

Treatment

Medical treatments can help decrease the symptoms of Paget's disease, but there is no known way to reverse the effects on the bone.

If you aren’t experiencing symptoms, your doctor may only call for observation. Periodic X-rays may be recommended to watch for any changes.

If you are experiencing mild pain, nonsteroidal anti-inflammatories (NSAIDs) and aspirin can be very helpful. When the pelvis or leg is involved, using a cane can decrease pain by reducing the forces impacting the bone. A cane can also help prevent falls, so there is less risk of fracture. Braces may be used to prevent malalignment of the bones.

When bone pain is more significant, medications called bisphosphonates are the treatment of choice. These drugs block osteoclasts and can be very effective in treating Paget's disease. There are several types of bisphosphonates that are taken by orally or by injection. While using this medications, your alkaline phosphatase level should steadily decline, along with bone pain. Your levels should be checked periodically.

Surgery is primarily used to treat the complications of Paget's disease. You may need surgery if you have a fracture, badly aligned bone, or severe arthritis. You may also need surgery if enlarged bone compresses nerves, especially in the spine or skull. Because Paget’s diseases increases the blood supply to your bones, your doctor may recommend bisphosphonates before the surgery to reduce potential blood loss. Bones affected by Paget's disease may take longer to heal than normal bones. Longer rehabilitation than usual may be necessary.

In the rare cases of Paget's sarcoma, surgery is almost always used to try to remove the tumor entirely. Chemotherapy and radiation therapy may also be used.

 

Research on the Horizon
Scientists are currently investigating the genes that may be involved with Paget's disease. This work could enable doctors to predict who may be at risk for the disease and lead to new therapies to treat it. Eventually, doctors hope to reverse effects on the bone, instead of just slowing the effects.

Reproduced with permission Fischer S., (interim ed): Your Orthopaedic Connection. Rosemont, Illinois. Copyright American Academy of Orthopaedic Surgeons.