The Clinical Spectrum of McCune-Albright Syndrome and Its Management

Abstract

McCune-Albright syndrome (MAS) is a rare, mosaic disorder presenting along a broad clinical spectrum. Disease arises from somatic-activating GNAS mutations, leading to constitutive Gα s activation and ligand-independent signaling of the Gα s -coupled protein receptor. The phenotype is largely determined by location and extent of tissues in which the GNAS mutation is expressed, as well as the pathophysiologic effects of Gα s activation within these tissues. Patients pre-sent clinically with a variable combination of fibrous dysplasia of bone (FD), café-au-lait skin macules, and hyperfunctioning endocrinopathies. In bone, Gα s leads to impaired differentiation of skeletal stem cells and formation of discrete, expansile FD lesions, resulting in fractures, pain, and functional impairment. A systematic approach to diagnosis and management is critically important to optimize outcomes for patients with FD/MAS. There are no medical therapies capable of altering the disease course in FD; however, screening and treatment for endocrinopathies can mitigate some skeletal morbidities. This review summarizes current understanding of MAS pathophysiology, describes the spectrum of clinical features, and includes a detailed discussion of the recommended approach to diagnosis and management.