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McCune-Albright syndrome

McCune-Albright syndrome is a genetic disease that affects the bones and color (pigmentation) of the skin.

Causes

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.

Symptoms

The hallmark 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). Puberty and menstrual bleeding may begin 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:

Exams and Tests

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 too much:

Other tests that may be done include:

Genetic testing is available for the GNAS1 gene.

Treatment

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.

Outlook (Prognosis)

Lifespan is relatively normal.

Possible Complications

Complications may include:

When to Contact a Medical Professional

Call 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 recommended if the disease is diagnosed.

Alternative Names

Polyostotic fibrous dysplasia

References

Garibaldi LR, Chemaitilly W. Disorders of pubertal development. In: Kliegman RM, Stanton BF, St. Geme JW, Schor NF, eds. Nelson Textbook of Pediatrics. 20th ed. Philadelphia, PA: Elsevier; 2016:chap 562.

Styne DM, Grumbach MM. Physiology and disorders of puberty. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 25.

Review Date 8/16/2016

Updated by: Anna C. Edens Hurst, MD, MS, Assistant Professor in Medical Genetics at The University of Alabama, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.