Paget's disease is a common disorder of middle-aged and elderly people in which the normal process of bone formation is disrupted, causing the affected bones to weaken, thicken, and become deformed. Also known as osteitis deformans, Paget's disease usually involves only limited areas of the skeleton. The bones usually affected are the pelvis, skull, clavicle (collarbone), vertebrae, and long bones of the leg. The condition is named after the British surgeon James Paget.
Cause and incidence
The normal maintenance of healthy bones by the body involves a balance between the actions of cells that break down bone tissue and those that rebuild it. In Paget's disease, this balance is disturbed. The disease varies in frequency from one region to another, suggesting an infective cause, which is thought to be viral. Overall, Paget's disease affects about three percent of the population over the age of 40, the incidence increasing with age. The disease has a tendency to run in families and affects more men than women.
Symptoms and signs
Paget's disease often causes no symptoms and is usually discovered from an X-ray taken for some other reason. The most common symptoms are bone pain and deformity, especially bowing of the legs. Affected bones are prone to fracture.
Changes in the skull may lead to leontiasis (distortion of the face that produces a rather lion-like appearance) and to inner-ear damage, sometimes resulting in deafness, tinnitus (ringing in the ear), vertigo, or headaches. Enlarged vertebrae may press on the spinal cord, causing pain and sometimes paralysis of the legs. If the pelvis is affected, severe arthritis of the hips can result. Occasionally, bone cancer may develop, and, in rare cases, when many bones are involved, increased blood flow through the affected bones may cause heart failure.
X-rays reveal areas of porous, thickened bone. Blood tests that show an elevated level of the enzyme alkaline phosphatase (which is associated with bone cell formation) give an indication of the extent and activity of the disease.
Treatment and outlook
Most people with the disorder do not require treatment, and many others simply need analgesic drugs (painkillers). In severe cases, the hormone calcitonin may be prescribed. It relieves pain, reduces alkaline phosphatase levels, and promotes normal bone formation. Other drugs that have the same effect (including disodium etidronate and plicamycin) may also be used. Surgery may be required to correct deformities or to treat arthritis.