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Noonan syndrome can be caused by a genetic mutation in any one of several different genes.

Noonan syndrome can be caused by a genetic mutation in any one of several different genes.
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Noonan syndrome

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Noonan syndrome is a rare genetic condition present from birth. Most people affected by the syndrome can lead a normal life, although some treatments and therapies may be needed, especially in childhood.

What is Noonan syndrome?

Noonan syndrome is a genetic condition that can cause a range of problems. People with Noonan syndrome may be mildly affected, or more severely affected. How the disorder affects people with Noonan syndrome can change as they get older.

Noonan syndrome can be caused by a genetic mutation in any one of several different genes. In about half of all cases the condition is inherited, although the parent who passed the condition on to their child may not even know that they carry the faulty gene because they show no signs of the disorder. 

Symptoms or signs of Noonan syndrome

Noonan syndrome develops in a baby before birth. Sometimes, the disorder is diagnosed straight away, but some children with mild symptoms aren’t diagnosed until they get older. 

Common signs of Noonan syndrome include:

  • unusual facial features such as widely spaced eyes with drooping eyelids and low-set ears 
  • restricted growth causing shortness, delayed puberty and, in males, undescended testicles
  • medical problems such as heart defects, bleeding (clotting) abnormalities and bone deformities.

Some children with Noonan syndrome may experience intellectual disability or behavioural problems, such as clumsiness or irritability.

As babies with Noonan syndrome grow, their symptoms can change, and may become less noticeable as they reach adulthood. 

Diagnosing Noonan syndrome

Noonan syndrome is usually diagnosed by assessing key features of the disease. A blood test may also be taken for genetic testing. In some cases, further tests may be needed, such as heart investigations including an electrocardiogram (ECG) and echocardiogram (ultrasound).

If you are expecting a baby, you might be able to have prenatal tests done to test your unborn baby for Noonan syndrome. 

Living with Noonan syndrome

Most children with Noonan syndrome go on to lead normal lives in adulthood. However, a child newly diagnosed with the disorder may need a number of treatments, and regular tests to monitor their condition over time. The types of treatment and support required will depend on the problems they experience.

Where to go for help

If you have concerns, talk to your doctor. Additional support may also be available from:

More information

Visit our genetic disorders guide to learn more about genes, types of genetic disorders and where to go for help and more information.

Last reviewed: September 2016

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