Dysplasie fibreuse et syndrome de McCune-Albright

Abstract

Fibrous dysplasia of bone (FD) is a rare congenital but not heritable bone disease, that is characterized by the replacement of normal bone structure with abnormal fibro-osseous connective tissue. This disease is caused by activating mutation of GNAS. FD may cause bone pain, bone deformity and fractures. It can affect one bone (monostotic FD) or multiple bones (polyostotic FD). FD may either occur as an isolated condition or as part of the McCune-Albright syndrome (MAS), which is characterized by the following triad: FD, hyperfunctioning endocrinopathies (mainly peripheral precocious puberty), and/or café-au-lait spots. Diagnosis relies on bone imaging and if necessary on pathological examination on bone biopsy with GNAS mutation search. The prognosis is usually good in monostotic disease; polyostotic diseases can lead to bone pain and fractures with significant disabilities. Treatment starts with the management of pain; moreover, various uncontrolled studies have shown the interest of bisphosphonates on bone pain but probably also on the improvement of radiological images; a randomized placebo-controlled study did not demonstrate the efficacy of oral bisphosphonates so the preferred route is intravenous. Other therapeutics are being studied (in particular Tocilizumab and Denosumab) but controlled studies are needed. Endocrinological management is of course necessary in cases of McCune-Albright syndrome, especially in cases of precocious puberty. Finally, specialized orthopedic care will be essential for the prevention and treatment of fracture complications.