McCune-Albright syndrome (MAS) is a condition caused by mutations in the GNAS1 gene. It is characterized by a triad of bone abnormalities, patchy skin pigmentation, and endocrine hormonal abnormalities
Bones affected in MAS are typically thin and easily broken. The skin may be light or dark in color, and there may be areas of hair growth (hirsutism) or loss of hair (alopecia). The endocrine system presents with abnormal production of various hormones, which can result in precocious puberty, early menopause, or excessive amounts of thyroid hormone (hyperthyroidism).