McCune-Albright syndrome

Background

McCune-Albright syndrome is a rare genetic disorder affecting the bones and skin pigmentation. It is also associated with endocrine (hormone) problems, notably premature sexual development. In its classic form, McCune-Albright syndrome involves at least two of these features. Life expectancy is near normal.

Credits

Last updated February 2015 by Dr R Stanhope, Consultant Paediatric Endocrinologist, The Portland Hospital, London, UK.

Listen to more about the condition

McCune-Albright syndrome is a rare genetic disorder affecting the bones and skin pigmentation. In this podcast an adult talks about how McCune-Albright syndrome has affected her life. Click here to listen

The views expressed in this podcast are for information purposes only. The material is in no way intended to replace professional medical care or attention by a qualified practitioner. Condition symptoms may vary in type or severity amongst individuals. This podcast is to demonstrate the personal views and experience of this family only. For approved medical information about this condition see the Contact a family website or contact your doctor.

What are the symptoms?

The hallmark feature of McCune-Albright syndrome is premature puberty in females. Early development of breasts and pubic hair and an increased rate of growth are common. Periods may begin in early childhood, and are caused by oestrogens – chemicals secreted into the bloodstream as a result of the formation of ovarian cysts. The cysts and irregular menstrual bleeding may continue into adolescence and adulthood. Many adult women with McCune-Albright syndrome are fertile.

Early sexual development occurs less commonly in males, involving the development of testes, pubic and underarm hair and increased growth rate.

The spectrum of features has broadened to include problems associated with the heart and liver. Individuals can be differently affected by the range and severity of features. Some children may be affected by bone disease in early infancy and have a range of hormonal problems; others may be entirely healthy.

Many individuals with McCune-Albright syndrome have thyroid gland abnormalities including goitre (generalised enlargement) and irregular masses called nodules and cysts. Some individuals show an increased secretion of pituitary growth hormone which causes the coarsening of facial features, enlargement of hands and feet and arthritis. Less commonly, some affected individuals may have the features of Cushing syndrome.

Individuals with McCune-Albright syndrome also have polyostotic fibrous dysplasia (abnormal fibrous tissue growth in many bones). The severity of this is very variable and any bone in the body may be affected. When the polyostotic fibrous dysplasia occurs in weight-bearing bones, such as the femur (upper leg bone), limping, bowing, pain and sometimes fractures may result. If the bones that form the upper jaw and skull are affected, deafness or blindness can result from ‘pinched nerves’ and facial asymmetry. Some children are affected minimally and in others severe bone disease has a permanent effect upon mobility and physical appearance. Hypersecretion from the parathyroid glands (with elevated parathyroid hormone levels and raised serum calcium) may make the bone disease more severe.

Most children with McCune-Albright syndrome have café-au-lait spots (irregular, flat areas of increased skin pigment). These may be extensive and usually have irregular margins. They are different from the café-au-lait spots seen in neurofibromatosis. In dark skinned children, these spots may be difficult to see. The skin pigmentation is not present at birth, but usually from about a month to six weeks of age.

What are the causes?

McCune-Albright syndrome is caused by mutations (or changes) in the GNAS1 gene.

How is it diagnosed?

Diagnosis is based on the presence of skin pigmentation, premature puberty, and bone disease.

How is it treated?

Many of the problems a patient may develop will be dealt with by an endocrinologist with the help of an orthopaedic surgeon to treat bone deformity and fractures.

Inheritance patterns and prenatal diagnosis

Inheritance patterns

McCune-Albright syndrome is sporadic (no previous family history).

Prenatal diagnosis

It may be possible to perform chorionic villus sampling (CVS) or amniocentesis during pregnancy. Genetic counselling may be helpful for individuals and families affected by this condition.

Is there support?

Fibrous Dysplasia Support Society (FDSS)

Email: enquiries@fdssuk.org.uk
www.fdssuk.org.uk

The Society is a support network, established in 2007. It offers support and information to families affected by fibrous dysplasia and McCune-Albright syndrome. The Society runs an annual family conference providing the opportunity to meet other families.

Group details last updated February 2016.

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