Paget's disease of bone.

Paget's disease of bone is defined as a process of increased bone remodeling; the primary event is increased resorption (osteoclastic activity) followed by subsequent reactive bone formation (osteoblastic activity). It is usually asymmetric and may be asymptomatic. The etiology is unknown, but recent evidence appears to support the theory that a virus is an important etiologic factor. It may present with a wide variation in the clinical and radiographic picture. The most frequent sites of involvement include the spine, femora, cranium, pelvis, and sternum. The most common complaints are pain, skeletal deformity, and change in skin temperature. Pathologic fractures may be the presenting manifestations or complications in a patient with known Paget's disease. They occur most frequently in the long weight-bearing bones of the lower extremities such as the femoral neck and subtrochanteric and tibial regions. The two major therapeutic agents available for treatment are calcitonins (porcine, salmon, or human) and diphosphonates. The aim of such therapy is to control the metabolic activity of the disease, to normalize the biochemical parameters, and to improve the symptoms. Fortunately, tumors are rare; early diagnosis may give rise to more effective palliation, if not a significant cure rate.