Paget's disease is the second most common bone disease. Paget's disease is a chronic bone disorder that is due to irregular breakdown and formation of bone tissue.The disease occurs worldwide, but is more common in Europe, Australia, and New Zealand -- where it is seen in up to 5% of the elderly population. Paget's disease can cause bones to expand and weaken and may result in bone pain, arthritis, bone deformity and fractures. Men and women are approximately equally affected. The prevalence of Paget's disease ranges from 1.5 to 8% depending on age and country of residence. The prevalence of familial Paget's disease (where more than one family member has the disease) ranges from 10 to 40% in different parts of the world. It is usually localized to one bone, but can involve many bones. The actual cause of Paget's disease is not known. Paget's disease is also known as osteitis deformans. The disease may localize to one or two areas within the skeleton, or become widespread. Frequently, bones of the pelvis, leg, spine, arm, or the collar bone are involved. The effect on the skull may enlarge head size and cause hearing loss, if the cranial nerves are damaged by the bone growth.

Paget's disease may affect only one or two areas of your body, or may be widespread. Paget's disease tends to appear in families. It can be present in as many as 25 percent to 40 percent of the relatives of someone with the disease. It is also more common in people of Anglo-Saxon descent. Many patients do not know they have Paget's disease because they have a mild case with no symptoms. Sometimes, symptoms may be confused with those of arthritis or other disorders. Symptoms can arise from the effect on calcium levels in the blood stream. When Paget's disease is active in several bones, the overactive osteoclasts can release enough calcium from the bone as they break it down to cause an elevated calcium level in the blood. This rare complication might cause fatigue, weakness, loss of appetite, abdominal pain, or constipation. A doctor can also detect Paget's disease from its effect on the heart if excess blood supply is shunted to overactive bones in severe cases. When pain is severe and unrelenting in an area affected by Paget's disease, the disease may have degenerated into a bone cancer. Paget's sarcoma (Figure 6) 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.

Paget's disease occurs most frequently in the spine, skull, pelvis, thighs, and lower legs. Paget's disease may be caused by a slow virus infection (i.e., paramyxoviruses such as measles and respiratory syncytial virus). Paget's disease of bone, though they have discovered several genes that appear to be linked to the disorder. Hereditary factors seem to influence whether you're susceptible to the disease. Environmental factors may also play a role. Several studies have postulated that viruses, particularly paramyxoviruses such as canine distemper or measles virus, play a role in pathogenesis, but definitive evidence for this is lacking. Presumably, the declining incidence of Paget's disease reflects a decline in one or more as yet unidentified environmental influences. The SQSTM1/p62 protein is a selective activator of the transcription factor NFB, which plays an important role in osteoclast differentiation and activation in response to the cytokines RANK-ligand and interleukin-1.Mutations in the SQSTM1/p62 gene are therefore a plausible cause of Paget's disease. Germline DNA mutations (present in every osteoclast) cause bone disease that is focal in nature.

Medical are generally treating Paget's disease. Treatment include is aspirin, other anti-inflammatory medications, pain medications, and medications that slow the rate of bone turnover, such as calcitonin (Calcimar, Miacalcin), etidronate (Didronel), alendronate (Fosamax), and pamidronate (Aredia). Surgery is used mainly to treat the complications of Paget's disease. A newer drug, risedronate (Actonel), appears to have a powerful effect against severe Paget's disease. Miacalcin is administered by injection; 50 to 100 units daily or 3 times per week for 6-18 months. Didronel (etidronate disodium) -- Tablet; approved regimen is 200-400 mg once daily for 6 months; the higher dose (400 mg) is more commonly used; no food, beverages, or medications for 2 hours before and after taking. Fosamax (alendronate sodium) -- Tablet; 40 mg once daily for 6 months; patients should wait at least 30 minutes after taking before eating any food, drinking anything other than tap water, taking any medication, or lying down (patient may sit). Eating a healthy diet with sufficient calcium and vitamin D and getting exercise are important components in maintaining skeletal health and joint mobility.