Paget's Disease (Osteitis Deformans)

Paget's disease is a chronic disorder in which bone metabolism goes awry. Instead of an orderly, constant process of repair and replacement, there is rapid loss, or resorption, of calcium and other bone minerals. The marrow is then replaced by fibrous tissue and a proliferation of blood vessels, their growth often rapid and chaotic. The new bone has an abnormal structure; it is less compact and contains more blood vessels than normal bone. As a result, the affected bones may, in time, become enlarged and so weak that they break spontaneously.

The disease can exist for years without producing obvious symptoms, so its incidence is difficult to gauge. Experts estimate, however, that about 3 percent of people over the age of 40 have some degree of Paget's disease. The incidence is proportionally higher among older people.

The cause of Paget's disease remains unknown, but a genetic predisposition as well as a viral trigger have been implicated. Among candidates for the viral trigger are respiratory syncytial virus, an organism that can cause bronchitis and pneumonia, and the measles virus. Also, an association between dog ownership and Paget's disease in one area of England has led some researchers to speculate that a canine virus may be involved.

Symptoms vary according to the site of the disease, but bone pain is common. The bones most often affected are the tibia (shin bone), femur (thigh bone), pelvis (hip bone), vertebrae, and skull. In some severe cases, thigh bones become so soft that (hey bend outward and the shins bend forward. In others, the head becomes visibly larger. If the leg and hip bones are deformed, lower back pain often radiates to the buttocks and legs, and walking may be difficult. Bone changes affecting the inner ear may lead to deafness; facial pain and headaches are also common.

The proliferation of blood vessels in pagetic bone increases blood flow to the extremities, which may feel unusually warm to the touch. If the disease affects more than one-third of the skeleton, the heart must pump harder to meet the needs of the extra blood vessels, which can lead eventually to heart failure. In some cases, there are severe deformities of the spinal column, which compress the spinal cord and cause neurological symptoms, such as numbness or paralysis of a limb.

Diagnostic Studies and Procedures

Paget's disease is often discovered when X-rays taken for some other purpose show the characteristic mosaic pattern of bone tissue. In other instances, investigation of hearing loss, facial nerve pain, or other symptoms seemingly unrelated to the bones may uncover the abnormality.

Blood and urine tests also provide clues of abnormal bone metabolism. Bone scans with a radioactive substance confirm a diagnosis. Additional tests or scans may be ordered to look for sarcomas, a type of bone cancer that is a possible complication of Paget's disease. An electrocardiogram and other heart studies may reveal a higher-than-normal cardiac output.

Medical Treatments

Drug Therapy. When Paget's disease is asymptomatic, treatment is unnecessary. If pain is the major problem, large doses of aspirin provide relief and appear to suppress the disease itself. Similar results are achieved with other non-steroidal anti-inflammatory drugs (NSAlDs), especially indomethacin (lndocin).

Steroids such as prednisone also suppress the disease, but because they must be given in high doses that can produce serious side effects, including lowered immunity, they are not recommended except as short-term treatment. A drug used specifically for Paget's disease, etidronate (Didronel), is sometimes prescribed to slow the rate at which bone is broken down and rebuilt.

Injections of calcitonin, a thyroid hormone, decrease resorption of bone that has been broken down by the body. If etidronate and calcitonin are ineffective, plicamycin (Mithracin), an intravenous anticancer drug, may be tried. This drug inhibits bone resorption, but its use in Paget's disease is considered experimental. Long-term calcitonin therapy can reduce bone pain and stabilize cardiac output.

Surgical Treatment. An osteotomy, or bone resection, may be recommended to correct a disabling deformity of the leg bones. Total hip replacement may be considered if the disease has caused serious impairment of those joints.

Alternative Therapies

Meditation and Self-hypnosis. These and other relaxation techniques may be helpful in alleviating pain.

Physical Therapy. A suitable level of physical activity is important in fostering proper bone metabolism and retaining mobility. A physical therapist can provide guidance in developing a realistic exercise program, and also may recommend braces and other protective devices to help prevent fractures.

T'ai Chi. These gentle movements are especially appropriate for patients with weakened bones. Some types of dance therapy may have similar benefits.

Self-Treatment

Avoid prolonged bed rest, which will accelerate bone loss and resorption. If your doctor prescribes high-dose aspirin or stronger NSAIDs. make sure that you take the pills with food to minimize stomach upset.

Other Causes of Bone Symptoms

Osteoporosis produces bone changes and pain similar to some aspects of Paget's disease.