Paget's Disease
Definition of Paget's Disease
This is a common, nonmetabolic disease of bone of unknown cause. It usually affects middle-aged and elderly people and is characterized by excessive bone destruction and unorganized bone repair.
Description of Paget's Disease
Throughout life, the skeleton is constantly remodeled. Large cells called osteoclasts secrete enzymes that break down or reabsorb bone. In healthy bone the activity of osteoclasts is balanced by that of osteoblasts, cells that secrete collagen and other proteins needed to form new bone.
Paget's disease develops when abnormally large pagetoid osteoclasts resorb areas of bone at a faster rate than usual. In trying to make up for this accelerated loss, the osteoblasts form irregularly patterned new bone that is weaker, although often thicker, and contains more blood vessels than normal.
Causes and Risk Factors of Paget's Disease
Researchers do not know what causes Paget's disease. The disorder seems to be relatively common in North America and Europe and is rare in the Middle East and Far East.Some scientists believe that a viral infection may be to blame, but they have not been able to isolate a virus. Other researchers favor a genetic explanation because as many as 30 percent of people with Paget's have a close relative who also has the disease.
Symptoms of Paget's Disease
Most cases are asymptomatic and mild. However, bone pain may be the first symptom. Bowed tibias (saber shins), kyphosis, and frequent fractures are caused by the soft, abnormal bone in this condition.Most people find out that they have Paget's disease by accident. This sometimes happens when a routine blood test turns up an elevated level of alkaline phosphatase, an enzyme produced in excess when osteoblasts are overworked. Or a radiologist may notice pagetoid lesions on a x-ray for something else.
The bones most likely to be affected are the spine, pelvis, skull, tibia (the shin bone), femur (the thigh bone), and humerus (the arm bone stretching from the shoulder to the elbow).
When a blood test turns up an elevated level of alkaline phosphatase, a bone scan is ordered to help rule out other possibilities such as metastatic cancer that has spread to the bone. In most cases, Paget's disease progresses so slowly that x-rays taken at yearly intervals will show little change.
Doctors estimate that about 10 percent of people who have Paget's disease experience symptoms. Dull, aching pain that occurs when the nerves are compressed by small fractures or thickened patches of pagetoid bone is most common. Some people develop arthritis-like symptoms when Paget's disease affects a joint. Others notice an unpleasantly warm patch of skin over a pagetoid lesion due to an increased blood flow to the area. In some cases, a visible deformity such as a thickened skull or curvature of the thigh or shin bone develops.
One in five people who have symptoms will experience more serious complications. These problems are most likely to occur when Paget's disease affects the skull. Thickened bone may impinge on a vital nerve and cause deafness, numbness of the face, or, in rare cases, blindness.
When Paget's disease develops in the jaw, dental extractions may be complicated by excessive bleeding.
Very rarely, people with Paget's disease get osteosarcoma, a form of bone cancer.
Diagnosis of Paget's Disease
Paget's disease is diagnosed based upon its characteristic history, clinical findings and findings on x-ray.
Treatment of Paget's Disease
Doctors do not treat Paget's disease unless a person has symptoms. For pain relief, nonsteroidal anti-inflammatory drugs like aspirin and ibuprofen are usually effective.
When Paget's disease impinges on the spinal cord or thickens the skull, more aggressive treatment is required to inhibit bone resorption. Doctors have a choice of two types of drugs, bisphosphonates or calcitonins, which both work by inhibiting osteoclast activity.
Two bisphosphonates are approved for the treatment of Paget's disease in the U.S.: etidronate (Didronel) and pamidronate (Aredia), which must be injected.
Two versions of synthetic calcitonin - human and salmon - are available. Both forms must be injected.
Because etidronate inhibits both bone formation and resorption when taken for long periods, doctors typically prescribe the drug for four to six months followed by a four-to-six month rest.
Pamidronate is administered intravenously as a single four-hour infusion for three consecutive days. For severe cases, the treatment is repeated six to nine months later.
When calcitonin is used, patients need to give themselves a daily injection, which is tapered to two to three times a week or discontinued altogether when alkaline phosphatase levels have fallen.
Each drug may have unpleasant side effects. Etidronate and pamidronate can cause nausea and diarrhea and can exacerbate bone pain in some people who have extensive Paget's disease. Calcitonin occasionally causes pain at the injection site, abnormal taste sensation, flushing, and nausea. Calcitonin is twice as expensive as etidronate, which costs about $50 a month.
Sometimes, the drugs are used alternately when people do not respond to either taken alone. Physicians monitor whether or not a particular treatment is effective by measuring alkaline phosphatase levels.
Questions To Ask Your Doctor About Paget's Disease
Is the diagnosis Paget's disease?
Is this a matter of concern?
Is treatment necessary?
What drugs will you prescribe?
What are the possible side effects of these drugs?
Will these control the abnormal bone formation and resorption?
Is there a cure?
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