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Paget's Disease of Bone

Paget's disease is a patchy disorder of the skeleton, usually occurring in adults over the age of 40 years. Increased bone turnover, thought to be caused by paromyxoviral infection of osteoclasts, causes localized bone resorption followed by haphazard production of new bone.

Any skeletal site may be involved, although the spine, pelvis, skull, and large bones of the extremities are most often affected. Paget's disease is associated with pain in involved bones; bowing of affected weight-bearing bones; degenerative arthritis of the hips, spine and ankles; pathologic fractures; and compression of nerves or spinal cord by the bony enlargement. Headache and deafness may be complications of cranial involvement. However, many patients, even some with extensive Paget's disease.

The diagnosis of Paget's disease is usually suspected because of symptoms, an elevated alkaline phosphatase level, or X-ray abnormalities. The radiographic features of mixed lytic and sclerotic areas with enlargement of the bone are generally sufficient to confirm the diagnosis, but biopsy of bone may be necessary if lytic lesions are isolated. Bone scan is useful to identify the distribution of pagetic activity in a patient. Serum alkaline phosphatase and urinary hydroxyproline levels reflect total pagetic activity and are very useful in monitoring response.

Therapy to decrease osteoclastic bone resorption is indicated in patients who have symptoms involving the skull or weight-beating long bones, have widespread distribution of skeletal lesions, and will be undergoing orthopedic surgery involving pagetic bone. Increased calcium intake and postmenopausal estrogen replacement therapy.

Suppression of osteoclastic activity with salmon calcitonin or etidronate was the mainstay of therapy. These drugs are moderately effective, reducing alkaline phosphatase activity by 40-50%. The current drugs of choice are two new bisphosphonate drugs, pamidronate (given intravenously) and alendronate, which are much more effective inhibitors of bone resorption and pagetic activity.