Medical Therapy in Adults With Fibrous Dysplasia of Bone

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Abstract
In open studies, bisphosphonate therapy (pamidronate, alendronate) reduced bone pain associated with fibrous dysplasia of bone and was associated to some radiological improvement. Calcium, vitamin D, and phosphorus supplements may be useful in patients with deficiency. We are awaiting results from controlled trials testing bisphosphonates. Introduction: Fibrous dysplasia of bone (FD), a rare disease caused by osteoblastic lineage differentiation defects, is associated with bone pain, fracture, and bone deformity, but few therapeutic options are available. Materials and Methods: We reviewed published data on the treatment of FD with bisphosphonates (pamidronate, alendronate), calcium, vitamin D, and phosphorus. We also present new results on FD therapy with a more potent bisphosphonate, zoledronic acid, given intravenously at the dose of 4 mg every 6 months. Results: Pamidronate therapy, given intravenously every 6 months at a dose of 180 mg in adults, relieved bone pain, decreased bone resorption, and improved the radiological aspect (filling of lytic lesions and/or thickening of cortices) in ∼50% of patients. BMD in affected sites was also significantly increased after pamidronate treatment. Those results have been obtained only in open studies, without controls, by several research groups. In a series of nine patients on long-term pamidronate treatment, but resisting to this medication and switched to intravenous zoledronic acid, no substantial improvement was observed. There is some biological rationale supporting the use of calcium and vitamin D in patients with deficiency to improve FD lesions by limiting secondary hyperparathyroidism. Phosphorus supplementation may prevent mineralization defects in those patients who have both FD and renal phosphate wasting. However, we are lacking clinical evidence for the efficacy of such supplements. Conclusions: Bisphosphonate treatment reduces increased osteoclastic activity in FD and probably improves bone pain, but their use should be better studied in randomized controlled trials.

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