Noonan syndrome - Symptoms, Causes and Treatment


Noonan syndrome is a genetic (inherited) condition that causes symptoms and problems in several parts of the body, including the head, heart and limbs (hands and feet).

Noonan syndrome can cause distinctive facial features, including a prominent forehead. Heart problems in patients with Noonan syndrome include congenital (the child is born with it) valve problems as well as thickening of the heart muscles.

Noonan syndrome 

Who is likely to have Noonan syndrome?

Anyone can be born with Noonan syndrome. The condition is more common among people whose parents have Noonan syndrome

Noonan syndrome occurs in 1 of every 1,000-2,500 people.

What causes Noonan syndrome?

Noonan syndrome occurs because of certain mutations (changes) on specific genes inherited from a person’s parents, including the genes PTPN11, SOS1, RAF1, RIT1, and KRAS. Approximately 50 percent of people with Noonan syndrome have a parent who also has the condition.

These genetic changes can also occur randomly. In 60 percent of cases, Noonan syndrome occurs from spontaneous genetic mutations that have no known cause.

What are the signs and symptoms of Noonan syndrome?

Noonan syndrome causes a variety of symptoms and problems, depending on which body systems or structures are affected:

Head and neck

  • Large head with a deep groove in the middle of the upper lip, small jaw, improperly aligned teeth, and ears pointed backward
  • Blue or bluish-green eyes that are widely set, turn in or out (strabismus), or have unusually thick or drooping eyelids (ptosis)
  • Webbing of the neck and a low hairline on the back of the neck


  • Pulmonary stenosis (a blockage of blood flow from the heart to the lungs), atrial septal defect (an opening between the upper heart chambers), and hypertrophic cardiomyopathy (thickening of the heart muscle)


  • Bulging finger pads or toes, misshapen or discolored nails, and changes in hair texture

Other problems/symptoms

  • Lymphedema (a buildup of fluid that causes swollen hands or feet)
  • In infants, failure to thrive (feeding problems and failure to gain weight and grow)
  • Short stature
  • Scoliosis (abnormal curvature of the spine)
  • Pectus excavatum, an abnormal development of the rib cage in which the sternum (breastbone) grows inward, resulting in an indentation of the chest wall
  • Delayed puberty, undescended testes, or infertility (inability to produce children)
  • Intellectual disabilities
  • Vision problems or hearing loss
  • Bleeding problems

How is Noonan syndrome diagnosed?

A doctor can diagnose Noonan syndrome with a physical examination and a review of the symptoms. In some newborn babies, Noonan syndrome is often suspected by the baby’s appearance.

The doctor may order tests to identify genetic mutations or to look for heart defects.

How is Noonan syndrome treated?

Doctors treat patients according to their specific symptoms and their causes. For instance, many people living with Noonan syndrome receive medications, surgery and supportive therapies like compression garments for lymphedema. Treatment may involve healthcare providers from several specialties working together to manage the symptoms.

What complications are associated with Noonan syndrome?

Noonan syndrome can cause intellectual disabilities and behavior or speech disorders. Some people who have Noonan syndrome may be more likely to develop certain cancers, like leukemia, later in their lives.

Can Noonan syndrome be prevented?

There is no way to prevent Noonan syndrome. Genetic mutations, either inherited from parents or occurring spontaneously, cause Noonan syndrome.

What is the prognosis (outlook) for people who have Noonan syndrome?

With treatment, most people who have Noonan syndrome lead healthy lives. Early diagnosis and treatment is key to managing symptoms and preventing complications.

What questions should I ask my doctor about Noonan syndrome?

If you or your child is diagnosed with Noonan syndrome, you may have many questions, including:

  • What tests will show if I have other complications, like heart problems?
  • What are the best treatment options for me?
  • Should I have genetic testing performed to determine my risk of passing on this condition?
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