Noonan Syndrome

What is Noonan syndrome?

Noonan syndrome is a rare genetic disorder that affects growth in various parts of the body, causing them to develop abnormally. It is characterized by multiple symptoms of varying severity; major ones include abnormal facial features, stunted growth, and heart defects. Noonan syndrome is typically evident at birth. It affects pproximately one in 1,000 to one in 2,500 people. It appears to affect more males than females.

What are the symptoms of Noonan syndrome?

Noonan syndrome has a spectrum of symptoms and physical features that vary widely in range and severity. So, the symptoms will not appear exactly the same from person to person.

• Distinctive facial features:
  • Wide-set eyes that are usually pale blue or green
  • Drooping of the upper eyelids
  • Deep grove in the area between the nose and the mouth
  • High arch in the roof of the mouth
  • Poor teeth alignment
  • A small lower jaw
  • Low-set ears, rotated backward
  • Depressed nasal root
  • Short nose with a broad base
  • Short neck with excess neck skin (webbing)
  • Low hairline at back of the neck
• Short stature and delayed growth
• Skeletal abnormalities:
  • Sunken or protruding chest
  • Curvature of the spine
• Some form of congenital heart disease:
  • Pulmonary valve stenosis: narrowing obstruction of the valve that controls blood flow from the heart to the lungs
  • Hypertrophic cardiomyopathy: enlarges and weakens the heart muscle
• Excessive bruising, nosebleeds, or prolonged bleeding after an injury
• Delayed puberty in adolescent males
• Intellectual disability

What causes Noonan syndrome?

Noonan syndrome is acquired when a child inherits a copy of a mutated gene from a parent. It is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is all that is needed to cause the disorder. It can also occur as a spontaneous mutation, meaning that family history is not involved. The disease results from mutations in many different genes; the main ones are PTPN11, KRAS, SOS1 RIT1 and RAF1.

How is Noonan syndrome diagnosed?

Noonan syndrome is diagnosed using the following procedures:

• Before birth, based on results of fetal ultrasounds
• At birth or early infancy, based on a thorough clinical evaluation and identification of characteristic physical findings
• Cardiologists may diagnose Noonan syndrome in individuals who have congenital pulmonary valve stenosis
• Other heart and lung evaluations
• Blood testing
• Molecular genetic testing

It is important to note that those who only have minor and subtle characteristics may not receive a diagnosis until adulthood.

What are the treatments for Noonan syndrome?

Treatment for Noonan syndrome is dependent on the symptoms in each patient. There is no way to repair the gene changes that cause it. Management focuses on controlling the symptoms and complications based on the individual’s case. Treatment includes, but is not limited to:

• Medication or surgery for heart problems
• Growth hormone for treating short stature
• Physical and speech therapies
• Eye exams and hearing screenings
• Medication for bleeding and bruising
• Treatment for lymphatic problems
• Surgery for genital problems
• Genetic counseling

Where can I find out more about Noonan syndrome?

• National Organization for Rare Disorders (NORD)
• Mayo Clinic
• NIH
• Genetics and Rare Diseases Information Center