Noonan syndrome

Noonan syndrome is a genetic disorder that can cause a wide range of potential symptoms which can vary from person to person. The three most common symptoms are:

  • short stature
  • distinctive and unusual physical features, such as a wider than usual distance between the eyes and a triangular-shaped face
  • congenital heart disease, which is where a baby is born with one or more defects that affect the normal function of their heart

The severity of the symptoms of Noonan syndrome can range from mild to life-threatening.

The condition is usually diagnosed at birth, although milder cases may go undiagnosed until a child gets older.

Noonan syndrome is relatively uncommon. It is estimated that 1 in 1,000 to 2,500 children are born with it. It affects both sexes and all ethnic groups equally.

What causes Noonan syndrome?

Researchers have identified four specific genetic mutations that cause Noonan syndrome. A genetic mutation happens when the normal instructions that are carried in certain genes become scrambled. This means that some of the body’s processes don't work in the normal way.

However, it is unclear exactly how these mutations cause all the symptoms associated with Noonan syndrome.

There is currently no cure for Noonan syndrome, so treatment involves trying to manage the various symptoms and complications that can arise from the condition.


The outlook for children with Noonan syndrome depends on how serious their congenital heart disease is (although only 80% of children with Noonan syndrome will have congenital heart disease). Some types of congenital heart disease are mild and only require careful monitoring. Other types are life-threatening and require immediate emergency surgery.

However, due to advancements in heart surgery, almost all children with congenital heart disease will survive into adulthood. Most adults with Noonan syndrome do not require specialist medical care but may benefit from occasional cardiac follow-up. They are usually able to lead full and independent lives.

Copied with permission from NHS Choices