McCune-Albright syndrome is a genetic disease that affects the bones and color (pigmentation) of the skin.
Polyostotic fibrous dysplasia
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 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:
- Bone fractures
- Deformities of the bones in the face
- Irregular, large patchy cafe-au-lait spots, especially on the back
Exams and Tests
A physical examination may show signs of:
- Abnormal bone growth in the skull
- Abnormal heart rhythms (arrhythmias)
- 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:
- Adrenal abnormalities
- Too little parathyroid hormone (hyperparathyroidism)
- Too much 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 is available for the GNAS1 gene.
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:
- Cosmetic problems from bone abnormalities
- Osteitis fibrosa cystica
- Premature puberty
- Repeated broken bones
- Tumors of the bone (rare)
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.
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.