Curriculum · Metabolic and Endocrine and Diabetes Mellitus
McCune-Albright syndrome
What it is
McCune-Albright syndrome is a classic triad: precocious puberty, café-au-lait macules and polyostotic fibrous dysplasia. It is also known as the three P's, fibrous dysplasia of bone, café-au-lait skin spots and precocious puberty. The mode of inheritance is sporadic, from a mutation in the GNAS1 gene, and it is more common in girls. Its precocious puberty is peripheral, that is gonadotrophin-independent: sex steroids are secreted independent of hypothalamic GnRH and of pituitary LH and FSH, unlike central precocious puberty, which is a premature reactivation of the hypothalamic-pituitary-gonadal axis with increased secretion of GnRH. The other peripheral causes listed beside it are congenital adrenal hyperplasia, gonadal tumors, adrenal tumors, familial male limited precocious puberty and exogenous exposure to sex steroids.
How it presents
The classic presenting sign of the precocious puberty is vaginal bleeding. The other common endocrine association is hyperthyroidism. The café-au-lait macules are worth telling apart from those of neurofibromatosis. In McCune-Albright syndrome they have coast of Maine borders, irregular, and never cross the midline. In neurofibromatosis they are coast of California, smooth, and cross the midline.