Section Editor: Sandy Cheng-Yu Chen, M.D.
Taipei Medical University Hospital, Taipei, Taiwan
McCune-Albright syndrome (MAS) is a rare genetic disorder resulting from postzygotic somatic mutations in the GNAS gene and is usually diagnosed during childhood or adolescence. It is manifested clinically by the triad of monostotic or polyostotic fibrous dysplasia, precocious puberty, and café-au-lait skin macules. Typical image findings of MAS include uni- or multifocal expansile bone lesion(s) with variable fibrous stromal matrix exhibiting a characteristic ground-glass opacity or a mottled and heterogeneous “pagetoid” appearance (A). Craniofacial involvement can lead to calvarial deformity and facial disfigurement (B) (previously described as leontiasis ossea in severe cases), and can develop entrapment syndromes due to anatomic alterations of cranial foramina, resulting in vascular or neurologic compromise (C).