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McCune-Albright syndrome

Polyostotic fibrous dysplasia

 

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:

  • Bone fractures
  • Deformities of the bones in the face
  • Gigantism
  • 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)
  • 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:

  • 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.

 

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:

  • Blindness
  • Cosmetic problems from bone abnormalities
  • Deafness
  • 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.

 

 

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.

 
  • Anterior skeletal anatomy

    Anterior skeletal anatomy - illustration

    The skeleton is made up of 206 bones in the adult and contributes to the form and shape of the body. The skeleton has several important functions for the body. The bones of the skeleton provide support for the soft tissues. For example, the rib cage supports the thoracic wall. Most muscles of the body are attached to bones which act as levers to allow movement of body parts. The bones of the skeleton also serve as a reservoir for minerals, such as calcium and phosphate. Finally, most of the blood cell formation takes places within the marrow of certain bones.

    Anterior skeletal anatomy

    illustration

    • Anterior skeletal anatomy

      Anterior skeletal anatomy - illustration

      The skeleton is made up of 206 bones in the adult and contributes to the form and shape of the body. The skeleton has several important functions for the body. The bones of the skeleton provide support for the soft tissues. For example, the rib cage supports the thoracic wall. Most muscles of the body are attached to bones which act as levers to allow movement of body parts. The bones of the skeleton also serve as a reservoir for minerals, such as calcium and phosphate. Finally, most of the blood cell formation takes places within the marrow of certain bones.

      Anterior skeletal anatomy

      illustration

    A Closer Look

     

      Talking to your MD

       

        Self Care

         

          Tests for McCune-Albright syndrome

           

             

            Review Date: 8/16/2016

            Reviewed 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.

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