Background Information
The McCune-Albright syndrome, or Albright disease, is disorder of bone, skin, and endocrine gland dysfunction. It has widespread effects on the body as a result of abnormal functioning hormonal glands including the thyroid, pituitary, adrenal, and sex glands. This causes bony overgrowth including those of the skull which causes narrowing of the tunnel through which the optic nerve passes. When the optic nerve is compressed as a result, it can cause blindness. Hearing may be affected by the same mechanism. However, all bones of the body are affected causing multiple deformities. The skin develops large pigmented patches called caf?-au-lait spots. Often there is considerably asymmetry of lesions and bony overgrowth between the two sides of the body. Early puberty may occur in both sexes. The metabolic basis of these effects remains unknown.This is generally not a familial disorder although several large pedigrees of individuals that may have had this disorder have been reported and these suggest autosomal dominant inheritance. Even though this is generally not a heritable disorder, a single gene (
GNAS
) is involved. Mutations in
GNAS
occurs early in development so that only some cells carry the mutant gene. The variable clinical picture results from the differences in number and location of cells among individuals in whom the mutation happened. The mutation is seldom passed on to offspring.
Mutations in the
GNAS
gene also cause Albright hereditary osteodystrophy (AHO), which is characterized by short stature, obesity, unusually short fingers and toes (brachydactyly), ectopic development of bony tissue under the skin, and other skeletal abnormalities. When a mutation that causes AHO is inherited from a person's mother, the affected individual will usually have AHO accompanied by a resistance to multiple hormones (a condition called pseudohypoparathyroidism type Ia, or PHPIa). A paternally-inherited mutation can result in AHO without endocrine problems; this form of the condition is also called pseudopseudohypoparathyroidism (PPHP).
Molecular genetic testing for
GNAS
is available.