McCune-Albright syndrome (MAS) is a rare, genetic, non-inherited condition that causes bone tumors, bone deformity and fractures. The manifestations include polyostotic fibrous dysplasia, café au lait spots, and precocious puberty.Mutation of the GS gene in chromosome 20q13 occurs early in development, and results in a mosaic of abnormal and mutated cells. The manifestations of MAS in each individual depend upon the extent and distribution of abnormal cells.