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Noonan syndrome

6-minute read

Key facts

  • Noonan syndrome is a rare genetic condition present from birth.
  • Young children with Noonan syndrome have facial features, for example: drooping eyelids, flat nose bridge, and low ears.
  • People with Noonan syndrome can also have heart, digestive or other health problems.
  • Your doctor can diagnose Noonan syndrome by doing a blood test.
  • Treatment for Noonan syndrome focuses on managing symptoms and health complications.

What is Noonan syndrome?

Noonan syndrome is a rare genetic condition present from birth. It causes a distinctive appearance and a range of health problems. Noonan syndrome can affect people in different ways. Some people can be mildly affected, others are more severely affected. How Noonan syndrome affects people can also change as they get older.

What causes Noonan syndrome?

Noonan syndrome is caused by a genetic mutation in any one of several different genes. About half of all people with Noonan syndrome inherited it from a parent. Often the parent that passed the condition on to their child does not even know that they carry the faulty gene. This is because they do not have any symptoms of the disorder, or their symptoms are very mild.

What are the symptoms of Noonan syndrome?

Children with Noonan syndrome can have symptoms including characteristic facial features and health problems. They are often shorter than expected for their age. Adults may also be short in stature.

Classic facial features of Noonan syndrome are easier to recognise in young children. They are less noticeable as children get older and reach adulthood. These features include:

  • drooping or hooded eyelids
  • bright blue or blue-green eyes that slope or are widely spaced
  • a flat nose bridge
  • strongly arched (diamond-shaped) eyebrows
  • low-set ears that tilt back
  • coarse, curly hair with a low hairline at the neck
  • a short neck with extra skin folds at the back

Health problems people living with Noonan Syndrome can have:

  • heart disease and heart defects
  • bleeding (clotting) problems
  • muscle and bone abnormalities — low muscle tone, unusually shaped chest, scoliosis, hypermobile joints
  • cancer — children are at a higher risk of developing leukaemia and some other cancers
  • gastrointestinal problems — swallowing problems, delayed gastric emptying (gastroparesis) — some may need a feeding tube
  • vision can be affected by drooping eyelids
  • hearing loss

Some children with Noonan syndrome may have intellectual disability or behavioural problems.

CHECK YOUR SYMPTOMS — Use the Symptom Checker and find out if you need to seek medical help.

How is Noonan syndrome diagnosed?

Your doctor can diagnose Noonan syndrome by observing your child’s appearance and health problems.

The diagnosis can be confirmed with genetic testing. This will involve a blood test. Sometimes, other tests may include heart checks including an electrocardiogram (ECG) and echocardiogram (ultrasound).

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

Sometimes, Noonan syndrome is diagnosed straight away at birth. Some children with mild symptoms are only diagnosed when they are older.

ASK YOUR DOCTOR — Preparing for an appointment? Use the Question Builder for general tips on what to ask your GP or specialist.

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Living with Noonan syndrome

There is no cure for Noonan syndrome. Each person living with Noonan syndrome receives individualised treatment to help manage their symptoms and health complications.

A health care team, made up of different medical professionals, may include specialist doctors and allied health professionals. They will work together to give the best care possible.

Some possible treatments include the following:

  • Physiotherapy — to treat weak muscles.
  • Speech therapy — helpful if there is a delay in speech development.
  • Growth checks — your child will have extra height, weight and growth checks and your doctor will prescribe growth hormone (GH) therapy if they need it. This will help them grow to normal height.
  • Blood tests — because some people with Noonan syndrome have problems with normal blood clotting, extra blood tests are needed after diagnosis, at 5 years old and before any procedure or surgery.

Most children with Noonan syndrome go on to lead normal lives in adulthood. A child newly diagnosed with the disorder may need a number of treatments. They may also need regular tests to monitor their condition over time.

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Last reviewed: December 2023

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