Health Library

What Is Noonan Syndrome?

Noonan syndrome is a condition that some babies are born with. It causes changes in the face and chest, usually includes heart problems, and slightly raises a child’s risk of blood cancer (leukemia).

Noonan

syndrome
is a pretty common condition, affecting 1 in 1,000–2,500 babies.

What Are the Signs & Symptoms of Noonan Syndrome?

Most children with Noonan syndrome have differences in the shape of their face and head. These are noticeable at birth and include:

• wide-set pale blue or blue-green eyes
• thick, low-set ears
• a thickened philtrum (the pair of ridges between the nose and the mouth) 
• loose skin on the neck or a short and broad neck
• a sunken breastbone (pectus excavatum) or bulging breastbone (pectus carinatum)
• boys: testes in the belly, not in the scrotum (undescended testicles)

They may also have:

• heart problems including:
  • pulmonic valve stenosis: when the pulmonary valve is too small, narrow, or stiff. (This valve is between the right ventricle and the pulmonary artery.) 
  • heart rhythm problems: when an ECG (heart rhythm tracing) shows that the heart is not beating regularly
• swollen hands and feet
• trouble feeding
• slow weight gain

Other differences as the child grows might include:

• starting to walk, talk, and other things later than most children
• vision and hearing problems
• learning and language problems
• slow growth
• short height
• easy bruising and bleeding a lot (from periods, nosebleeds, cuts, etc.) 
• late puberty

The symptoms of Noonan syndrome can be mild to severe. Two children with Noonan syndrome may have completely different symptoms and skills.

What Causes Noonan Syndrome?

A gene mutation (change) causes Noonan syndrome. Many different gene mutations can cause it.

Everyone has two copies of almost every gene. It only takes one changed gene to cause Noonan syndrome. In that case, children of a parent who has Noonan syndrome have a 50% chance of having it too.

Very rarely, changes in both copies of one gene can cause Noonan syndrome.

How Is Noonan Syndrome Diagnosed?

Doctors usually notice the features of Noonan syndrome at birth or soon afterward and suspect the diagnosis. The doctor will:

• ask about the family history of genetic conditions
• do an exam
• consider other genetic disorders with similar symptoms

Based on the results of these steps, the doctor will decide if a child may have Noonan syndrome.

A geneticist (a doctor who specializes in genetic disorders) will order a genetic test to see which mutation the child has. Knowing which gene changed can help doctors get a better idea about which symptoms will be most challenging for the child.

The doctors may also order these imaging tests:

• magnetic resonance imaging (MRI)
• computed tomography (CT) scan
• ultrasound
• echocardiogram (an ultrasound of the heart)

How Is Noonan Syndrome Treated?

There’s no cure for Noonan syndrome, but medical care can help with almost every symptom.

For example:

• Medicines and surgery can help heart problems. 
• Medicines or blood transfusions can treat bleeding.
• Growth hormone or other medicine can help speed up slowed growth.
• Surgery can correct undescended testicles.
• Education programs can help a child who has trouble learning.
• Many children will have trouble with speech and language. Working with a speech therapist before problems start can make these problems milder.

A team of doctors, nurses, therapists, and social workers provide care for a child with Noonan syndrome.

Meeting with a genetic counselor can help families:

• learn what to expect
• understand their chances of having another child with Noonan syndrome

What Problems Can Happen?

As they grow into adulthood, most children with Noonan syndrome have:

• a final adult height near the lower end of the average range
• heart problems that may get worse, so they need to see a heart specialist regularly
• a slightly higher risk of getting leukemia
• a life expectancy that usually depends on how well their heart is working

What Else Should I Know?

A child with Noonan syndrome who does not have serious heart problems usually:

• does very well with support
• reaches puberty and the teenage growth spurt later than most peers

The medical challenges of Noonan syndrome can be stressful for your child and you. But you’re not alone. The care team will work together to help manage problems, and to support your family. You can also ask about support groups, or visit online sites such as The Noonan Syndrome Foundation.