Fibrous dysplasia/McCune-Albright syndrome

A skeletal system disorder caused by a variation in the GNAS gene, characterized by involvement of the skin, skeleton and certain endocrine organs. Fibrous dysplasia ranges from an isolated monostotic lesion to severe polyostotic disease. McCune-Albright syndrome is diagnosed when fibrous dysplasia occurs with at least one extra-skeletal feature, or when two or more extra-skeletal features occur alone. The condition is not inherited. The signs and symptoms associated with the disorder vary greatly from person to person, depending upon the specific body cells and tissues that are affected by the gene variant.