Effect of Risedronate on Bone Morbidity in Fibrous Dysplasia of Bone

In open pilot studies, it has been suggested that bisphosphonates may alleviate bone pain and help decrease the surface of osteolytic lesion in patients with fibrous dysplasia of bone (FD). So, in this randomized placebo controlled trial, we test the hypothesis that the bisphosphonate risedronate reduces bone pain in patients with FD (study I, one year duration) and decrease osteolytic lesions (study II, three years duration). Patients will take risedronate during 2 months courses, every 6 months or a matching placebo. Dosage will be : 30mg tablet/day for adults and 5mg tablet x 2,4 according to the age and weight of the child. All participants will receive calcium and vitamin D. All patients with renal phosphate wasting will receive an oral phosphate supplement.