A genetic disease affecting the bones and pigmentation of the skin, and causing hormonal problems featuring premature sexual development.

Alternative Names

Polyostotic fibrous dysplasia; Osteitis fibrosa cystica

Causes, incidence, and risk factors

The hallmark of McCune-Albright syndrome is premature puberty in the female which may begin at variable ages. Sexual development is disordered in that menses may begin in early childhood long before the appearance of breast or pubic hair development. Early sexual development in the male is present, but it is not as common as in females. These children have abnormal fibrous dysplasia (abnormal fibrous development) in the bone that can lead to fractures , deformities and abnormal x-rays. Abnormal bone growth in the skull can lead to blindness or deafness due to "pinched" nerves. Deformity may appear in the facial bones causing cosmetic problems. In addition, the children have cafe-au-lait spots , which may be present from birth. McCune-Albright syndrome is caused by mutations in the GNAS1 gene. It is associated with mosaicism, meaning the abnormal gene is present in a fraction, but not all, of the patient cells. This disease is not inherited, it is sporadic. That is to say a new mutation of the DNA occurs in the womb during development of the patient but it is not passed on to children, perhaps because it is too severe for such child to survive.

Signs and tests

Physical examination may also show signs of:

hyperthyroidism

(occasional)

adrenal abnormalities (occasional)

acromegaly

(occasional)

Tests may show signs of hyperthyroidism, hyperparathyroidism, excess adrenal hormones, excess blood prolactin or growth hormone. X-rays show polyostotic (affecting multiple bones) fibrous dysplasia. MRI of the head may show a type of tumor called an adenoma in the pituitary gland. Genetic testing may be available for the GNAS1 gene.

Treatment

There is not a specific treatment for McCune-Albright syndrome. Drugs that inhibit estrogen production, such as testolactone, have been tried with some success. Adrenal abnormalities (such as Cushing syndrome) may be treated by surgery to remove the adrenal glands . Gigantism and pituitary adenoma will require treatment with hormone inhibitors or surgery.

Expectations (prognosis)

Longevity is relatively normal.

Complications

repeated episodes of broken bones

deformity and cosmetic problems resulting from bone abnormalities

blindness

deafness

tumors

Calling your health care provider

Call your health care provider if your child develops evidence of premature puberty (before the expected age) or has other symptoms suggestive of McCune-Albright syndrome. Genetic counseling and possibly genetic testing is indicated if the disease is diagnosed.

Prevention

No preventive measures are known for McCune-Albright syndrome.