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 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)
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
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.
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.