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Diseases

Genetic and Rare Diseases Information Center (GARD)

Other Names for this Disease
  • Albright syndrome
  • Albright's disease
  • MAS
  • PFD
  • POFD
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Your Question

Can you please provide some general information about McCune-Albright syndrome?

Our Answer

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What is McCune-Albright syndrome?

McCune-Albright syndrome (MAS) is a disease that affects the bones, skin, and several hormone-producing (endocrine) tissues.[1][2][3] It is characterized by replacement of normal bone tissue with areas of abnormal fibrous growth (fibrous dysplasia); patches of abnormal skin coloring with jagged borders (cafe-au-lait spots); and abnormalities in the glands that regulate the body's rate of growth, sexual development, and other metabolic functions (multiple endocrine dysfunction).[4] MAS is caused by a change (mutation) in the GNAS gene that occurs by chance very early in development. As a result, some of the body's cells have a normal version of the GNAS gene, while other cells have the mutated version. This phenomenon is called mosaicism. The severity of MAS and its features depend on the number and location of cells that have the mutated GNAS gene.[1] Because MAS occurs by chance, it is not inherited or passed down from one generation to the next.[1][3]
Last updated: 12/26/2013

What are the signs and symptoms of McCune Albright syndrome?

People with McCune Albright syndrome (MAS) may have symptoms related to bones, the endocrine system, and/or skin. The symptoms can range from mild to severe.[3]

Bone symptoms may include:
  • Polyostotic fibrous dysplasia: This is when normal bone is replaced by softer, fibrous tissue.[3] Polyostotic means the abnormal areas may occur in many bones; often they are confined to one side of the body.[1] Replacement of bone with fibrous tissue may lead to fractures, uneven growth, and deformity.[1][3] When it occurs in skull and jaw it can result in uneven growth of the face. This may also occur in the long bones; uneven growth of leg bones may cause limping.[1]
  • Abnormal curvature of the spine (scoliosis)[1]
  • Cancer: Bone lesions may become cancerous, but this happens in less than 1% of people with MAS.[1]

Endocrine symptoms may include:

  • Early puberty: Girls with MAS usually reach puberty early. They often have menstrual bleeding by age 2 (as early as 4-6 months in some), many years before characteristics such as breast enlargement and pubic hair growth are evident.[1][2][3] This early onset of menstruation is believed to be caused by excess estrogen, a female sex hormone produced by cysts that develop in one of the ovaries.[1] Less commonly, boys with MAS may also experience early puberty.[1][2][3]
  • Enlarged thyroid gland: The thyroid gland may become enlarged (a condition called a goiter) or develop masses called nodules. About half of affected individuals produce excessive amounts of thyroid hormone (hyperthyroidism), resulting in a fast heart rate, high blood pressure, weight loss, tremors, sweating, and other symptoms.[1][3]
  • Increased production of growth hormone: The pituitary gland may produce too much growth hormone. This can result in acromegaly, a condition characterized by large hands and feet, arthritis, and distinctive facial features that are often described as "coarse."[1][3]
  • Cushing’s syndrome: Rarely, individuals with MAS produce too much of the hormone cortisol in the adrenal glands. Cushing's syndrome causes weight gain in the face and upper body, slowed growth in children, fragile skin, fatigue, and other health problems.[1][3]

Skin symptoms may include:

  • Cafe-au-lait spots: Individuals with MAS usually have light brown patches of skin called cafe-au-lait spots.[1][3] Like the bone lesions, these spots often appear on only one side of the body.[1] Most children have these spots from birth and the spots rarely grow. There are usually not any medical problems caused by these skin changes.[3]
Last updated: 12/26/2013

How common is McCune-Albright syndrome?

McCune-Albright syndrome occurs in between 1 in 100,000 and 1 in 1,000,000 people worldwide.[1]
Last updated: 7/20/2009

What causes McCune Albright syndrome?

McCune Albright syndrome (MAS) is caused by a change (mutation) in the GNAS gene. This gene provides instructions for making part of a protein that ultimately influences many cell functions by regulating hormone activity. GNAS gene mutations that cause MAS result in a protein that causes the enzyme adenylate cyclase to be constantly turned on. This, in turn, leads to over-production of several hormones, resulting in the signs and symptoms of MAS.[1]
Last updated: 1/2/2014

Is McCune Albright syndrome inherited?

McCune Albright syndrome (MAS) is not inherited. It is caused by a random change (mutation) in the GNAS gene that occurs very early in development. As a result, some of the body's cells have a normal version of the GNAS gene, while other cells have the mutated version. This phenomenon is called mosaicism.[1][2] The severity of this disorder and its specific features depend on the number and location of cells that have the mutated GNAS gene.[1] This mutation is not passed on to any of the affected individual's children.[2]
Last updated: 12/26/2013

How might McCune Albright syndrome be treated?

Although there is no cure for McCune Albright syndrome (MAS), drug treatments may help some of the endocrine symptoms, and surgery can help repair some of the bone problems.[3] Generally, treatment depends on what tissues are affected as well as the severity.[5]

Surgery may be needed to manage complications associated with fibrous dysplasia, such as progressive visual disturbance, severe pain, and severe disfigurement. Surgery may also be needed to manage associated endocrine abnormalities and/or cancers. Bisphosphonates are frequently used to treat fibrous dysplasia. Strengthening exercises are recommended to help maintain musculature around the bones and minimize the risk of fracture. Treatment of all endocrine symptoms, whether by hormone inhibitors or surgery, is commonly required.[2][5]

More detailed information about the management of MAS syndrome is available on Medscape Reference's Web site.
Last updated: 1/2/2014

References