What is Noonan Syndrome?
Noonan Syndrome, once called Turner-like syndrome, is a genetic disease that can lead to abnormal physical development. An individual with Noonan syndrome may exhibit symptoms through unusual facial characteristics, stunted growth or stature, heart defects, and sometimes mild mental retardation. Approximately 1 in 1,000-2,500 people are affected.
Causes of Noonan Syndrome:
Noonan Syndrome is caused by genetic mutations; there are seven known genes that can trigger Noonan Syndrome. These genes assist in tissue formation, and create overactive proteins that can adversely affect cell growth. It is possible there are other, as-yet unknown genes that can cause this syndrome. In more rare cases, Noonan syndrome can be caused without any family history (spontaneous genetic mutation).
Risks for Developing Noonan Syndrome:
A child can inherit the gene mutation associated with Noonan Syndrome from either parent. Anyone with a family history of the disorder may want to seek genetic counseling prior to attempting to conceive.
Symptoms of Noonan Syndrome:
The following are the most common symptoms of the disorder:
- Facial features (wide set eyes, downward slanting of the eyes, or sagging eyelids)
- Heart defects (in about 50-70% of individuals)
- Congenital heart disease
- Delays in puberty onset
- Abnormal or stunted growth
- Hearing loss or vision problems
- Abnormally shaped ears
- Webbed or short neck
- Short stature
- Sunken or raised sternum
- Undescended testicles
- Learning disabilities
- Mild retardation (this is not as common; intelligence is not usually affected)
- Bruising or bleeding
- Lympathic or renal complications
Diagnosis of Noonan Syndrome:
Your doctor will perform a physical exam, and may check for signs of congenital heart disease. Other tests may be required, depending on which symptoms are present. This can include:
- Chest x-ray
- Hearing tests
- Platelet count
- Blood clotting factor test
- Molecular genetic testing
Treatment for Noonan Syndrome:
There is no specific treatment for Noonan Syndrome; however, doctors can treat symptoms and complications.
- Hormone therapy can be used to treat stunted or slow growth in children
- Physical or speech therapy
- Learning disability assistance
- Glasses or contacts for vision problems
- Hearing aids for hearing difficulties
- Chest tubes to drain excess fluids (associated with lympathic complications)
- Coagulants (for blood clotting problems)
- Antibiotics or surgery for heart valve defects or conditions
Approximately eighty percent of people who have Noonan syndrome also have congenital heart disease, which accounts for several of the key signs or symptoms. The most common forms of congenital heart disease associated with the disorder are:
- Valve disorders. Pulmonary valve stenosis is the narrowing of the pulmonary valve, which is the flap of tissue separating the lower right chamber of the heart supplying blood to the lungs. This defect is the most common heart problem seen in conjunction with Noonan syndrome.
- Hypertrophic cardiomyopathy. The thickening of the heart muscle, or abnormal growth, affects roughly twenty percent or more of people with Noonan syndrome.
- Structural defects. A hole in the wall separating the two lower chambers of the heart, called a ventricular septal defect, is one possible structural defect sometimes seen with Noonan syndrome. Another structural defect is pulmonary artery stenosis, which is a condition causing the narrowing of the arteries that carry blood to the lungs.
Many children with Noonan syndrome have difficulty with feeding, which can cause poor weight gain until closer to two years old. Growth spurts in adolescence may also be delayed as bone maturity is often slower.
An abnormality of the eyes and eyelids is a common sign of Noonan syndrome. A few of the eye problems include: eye muscle conditions such as strabismus or crossed eyes, refractive problems, astigmatism, nearsightedness (myopia), farsightedness (hypermetropia), and rapid movement of the eyeballs (nystagmus).
Many people with Noonan syndrome have problems with their genitals or kidneys, especially in males. However, kidney issues are typically mild. Puberty can sometimes be delayed, in both males and females, though females usually develop normal fertility. Male fertility may not develop normally, and often due to undescended testicles.
Additional Resources For Noonan Syndrome:
Noonan Syndrome Support Group - This organization provides history, news, stories, research information, support, and opportunities to donate. You can also reach the Noonan Syndrome Support Group by calling (888) 686-2224.
National Human Genome Research Institute - This site has a great deal of information on Noonan Syndrome, including news and research.
MUMS National Parent-to-Parent Network - A support group for parents to find other parents in their area whose lives have been touched by the same disorder or condition.
Mayo Clinic is a nonprofit worldwide leader in medical care and research for people from all walks of life. Their mission is to inspire hope and contribute to health and well-being by providing the best care to every patient through integrated clinical practice, education and research.