McCune-Albright syndrome
McCune-Albright syndrome
McCune-Albright syndrome is a genetic condition that affects bone growth, skin pigmentation and the body’s hormone balance. Bone abnormalities such as easily broken bones, and premature sexual maturity are typical signs of the condition. Symptoms range in severity.
In some cases, the bone abnormalities and hormone problems are severe enough to be obvious in infancy. In other cases, the child seems healthy in all respects. The severity of symptoms or how a child with McCune-Albright syndrome will be affected throughout life is difficult to predict.
There is currently no cure for McCune-Albright syndrome.
Symptoms of McCune-Albright syndrome
The symptoms and signs of McCune-Albright syndrome include:
polyostotic fibrous dysplasia – the abnormal growth of two or more bones. Bones of the face, skull, arms and legs are commonly affected
café au lait birthmarks, usually on the abdomen or back – these birthmarks are flat, oval-shaped spots with a jagged outline. Café au lait birthmarks are often the first signs of the condition and appear at or shortly after birth. They are light brown (or ‘milk-coffee coloured’) in people with lighter skin. In people with darker skin they may be harder to see
premature sexual maturity – this can affect girls and boys, but is much more common in girls
onset of the menstrual period before the growth of breasts or pubic hair
ovarian cysts, which are thought to trigger early menstruation
symptoms of an overactive thyroid gland (hyperthyroidism).
Complications of McCune-Albright syndrome
Some of the complications of McCune-Albright syndrome can include:
brittle, warped bones (osteoporosis)
repeated fractures
rickets
blindness or deafness due to abnormal growth of skull bones
adrenal gland tumours
osteitis fibrosa cystica – soft bones that are prone to developing cysts
mobility problems or disabilities caused by abnormal bone growth or asymmetry of the skeleton
in rare cases, excessive growth (gigantism) because of growth hormone imbalance – the face, hands and feet are commonly affected
Cushing’s syndrome.
Cushing’s syndrome
The hormone cortisol is made by the adrenal glands, which are located on the kidneys. McCune-Albright syndrome may cause enlargement of the adrenal glands and the overproduction of cortisol. This causes a range of symptoms collectively known as Cushing’s syndrome.
Some of the symptoms may include:
obesity
weight gain around the abdomen
wasting of the limbs
a hump of fat high on the back
round, red and puffy face
thin, easily bruised skin
slow healing of skin wounds
skin ulcers
arrested growth in childhood.
Causes of McCune-Albright syndrome
McCune-Albright syndrome is caused by a change in the GNAS1 gene . The change causes the GNAS1 gene to become more active than usual. The gene change is not inherited from the parents, nor is it present at the time of conception. The change actually occurs in an early cell division in the developing embryo. As a result, the change is present in some, but not all, cells of the person’s body. This is known as ‘mosaicism’.
Despite hormonal irregularities, most women with McCune-Albright syndrome are fertile. A person with McCune-Albright syndrome cannot pass the condition on to their children. The cause of the genetic change is not known.
Diagnosis of McCune-Albright syndrome
The tests used to diagnose McCune-Albright syndrome may include:
medical history
physical examination
blood tests to check hormone levels of the thyroid, parathyroid, adrenal glands and pituitary gland
x-rays to examine the skeleton
bone scan using an injection of radioactive material
other scans, such as MRI
genetic tests.
Treatment for McCune-Albright syndrome
There is no cure for McCune-Albright syndrome. Treatment may include:
medication to manage pain
surgery to bolster affected bones with grafts, pins, casts or a combination of procedures
treatment with medicines known as bisphosphonates to improve bone density
vitamin D supplements to reduce the risk of rickets
regular and supervised exercise program to improve bone density
physical therapy to maintain or improve joint mobility
medication to reduce levels of the female sex hormone oestrogen
surgery to remove ovarian cysts
surgery to remove abnormal adrenal glands in the case of Cushing’s syndrome
hormone therapy or surgery to treat a pituitary tumour
hormone therapy or surgery to treat gigantism.
Treatment team for people with McCune-Albright syndrome
Treatment depends on the person’s age, general health and severity of the symptoms. Specialist doctors may include an orthopaedic surgeon to treat bone problems, a plastic surgeon to treat facial deformities and an endocrinologist to treat hormone imbalances.
Genetic counselling and McCune-Albright syndrome
If your child has been diagnosed with McCune-Albright syndrome, it may be helpful to speak to a genetic counsellor.
Genetic counsellors are health professionals qualified in both counselling and genetics. As well as providing emotional support, they can help you to understand McCune-Albright syndrome and what causes it, and what a diagnosis means for your child’s health and development. Genetic counsellors are trained to provide information and support that is sensitive to your family circumstances, culture and beliefs.
The
Genetic Support Network of Victoria
(GSNV)
External Link
is connected with a wide range of support groups throughout Victoria and Australia and can connect you with other individuals and families affected by McCune-Albright syndrome.
Where to get help
Your
GP (doctor)
Orthopaedic surgeon
Plastic surgeon
Endocrinologist
Genetic Support Network of Victoria
(GSNV)
External Link
Tel.
(03) 8341 6315
Victorian Clinical Genetics Services
(VCGS)
External Link
Tel.
1300 118 247