McCune-Albright syndrome

McCune-Albright syndrome is caused by mutations in the GNAS gene. A small number, but not all, of the person's cells contain this faulty gene (mosaicism).

This disease is not inherited.

The main symptom of McCune-Albright syndrome is early puberty in girls. Menstrual periods may begin in early childhood, long before the breasts or pubic hair develop (which normally occur first). The average age that symptoms appear is 3 years old. However, puberty and menstrual bleeding have occurred as early as 4 to 6 months in girls.

Early sexual development may also occur in boys, but not as often as in girls.

Other symptoms include:

• Bone fractures
• Deformities of the bones in the face
• Gigantism
• Irregular, large patchy café au lait spots

A physical examination may show signs of:

• Abnormal bone growth in the skull
• Abnormal heart rhythms (arrhythmias)
• Acromegaly
• Gigantism
• Large cafe-au-lait spots on the skin
• Liver disease, jaundice, fatty liver
• Scar-like tissue in the bone (fibrous dysplasia)

Tests may show:

• Adrenal abnormalities
• High level of parathyroid hormone (hyperparathyroidism)
• High level of thyroid hormone (hyperthyroidism) 
• Adrenal hormone abnormalities
• Low level of phosphorous in the blood (hypophosphatemia)
• Ovarian cysts
• Pituitary or thyroid tumors
• Abnormal blood prolactin level
• Abnormal growth hormone level

Other tests that may be done include:

• MRI of the head
• X-rays of the bones

Genetic testing may be done to confirm the diagnosis.

There is no specific treatment for McCune-Albright syndrome. Drugs that block estrogen production, such as testolactone, have been tried with some success.

Adrenal abnormalities (such as Cushing syndrome) may be treated with surgery to remove the adrenal glands. Gigantism and pituitary adenoma will need to be treated with medicines that block hormone production, or with surgery.

Bone abnormalities (fibrous dysplasia) are sometimes removed with surgery.

Limit the number of x-rays taken of affected areas of the body.

Lifespan is relatively normal.

Complications may include:

• Blindness
• Cosmetic problems from bone abnormalities
• Deafness
• Osteitis fibrosa cystica
• Premature puberty
• Repeated broken bones
• Tumors of the bone (rare)

Contact your health care provider if your child starts puberty early, or has other symptoms of McCune-Albright syndrome. Genetic counseling, and possibly genetic testing, may be suggested if the disease is detected.

Polyostotic fibrous dysplasia

Garibaldi LR, Chemaitilly W. Disorders of pubertal development. In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA: Elsevier; 2020:chap 578.

Styne DM. Physiology and disorders of puberty. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 26.

Updated by: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.