[Osteitis deformans--Paget's disease].

Paget's disease of the bone is a disorder in which there is marked increase in bone turnover by activated osteoclasts in localized parts of the skeleton. The newly formed bone is abnormal in structure and mineralization resulting in deformity and increased risk of fracture. The prevalence of the disease has decreased over the last 20 years to 2% in patients over 55 years of age. The etiology of the disease is still unknown. There is strong evidence for viral infection, but recently a genetic disposition has also been discussed. There are important advances in the understanding of the pathophysiology of Paget's disease. increased sensitivity of osteoclast-precursors to 1,25(OH)2Vitamin D3 and RANKL, mediated by IL6 have been described as a possible mechanism. For the diagnosis of the disease the finding of an elevated level of plasma alkaline phosphatase as a marker of increased bone turnover is of great importance. This parameter is also used for monitoring disease activity during therapy. Plain radiology and skeletal scintigraphy are necessary for the diagnosis. CT and MRT can be useful in specific cases. In the last decade bisphosphonates have increasingly assumed--according to their mechanism of action--the prime role in the management of Paget's disease. Recently, more potent bisphosphonates have been developed and therefore the goal of therapy has changed. Initial response to treatment in terms of reducing activity of alkaline phosphatase to normal levels is associated with increased remission duration. In this respect, risedronate and alendronate have proved superior to etidronate. Bisphosphonates have also been used extensively in the form of intravenous infusion in patients with Paget's disease. Especially when gastro-intestinal side-effects occur with oral medication, this might be useful. However, at present more studies are needed to find the optimal drug, the optimal dose and intervals of i.v. therapy.