Noonan syndrome is a disease that can be passed down through families (inherited). It causes abnormal development in many parts of the body. Noonan syndrome used to be called Turner-like syndrome.
Causes, incidence, and risk factors
Noonan syndrome is linked to defects in several genes. Problems with the genes cause certain proteins involved in growth and development to become overactive.
Noonan syndrome is an
- Delayed puberty
- Down-slanting or wide-set eyes
- Low-set or abnormally shaped ears
- Mild intellectual disability (only in about 25% of cases)
- Sagging eyelids (
ptosis) Short stature
- Small penis
- Undescended testicles
- Unusual chest shape (usually a sunken chest called pectus excavatum)
- Webbed and short-appearing neck
Signs and tests
The health care provider will perform a physical exam. This may show signs of congenital heart disease (especially
Tests depend on the symptoms, but may include:
- Platelet count
- Blood clotting factor test
EKG, chest x-ray, or echocardiogram
- Hearing tests
Genetic testing can help diagnose this syndrome.
There is no specific treatment. Your doctor will suggest treatment to relieve or manage symptoms. Growth hormone has been used successfully to treat short stature in some persons with Noonan syndrome.
The Noonan Syndrome Support Group, Inc. —
- Buildup of fluid in tissues of body (lymphedema, cystic hygroma)
- Failure to thrive in infants
- Low self-esteem
- Male infertility in those with both testes undescended
- Problems with the structure of the heart
- Short stature
- Social difficulties related to physical symptoms
Calling your health care provider
This condition may be detected on early infant exams. Evaluation by an experienced geneticist is often needed to diagnose Noonan syndrome.
Couples with a family history of Noonan syndrome may want to consider genetic counseling before having children.