Noonan syndrome is a genetic disorder that prevents normal development in various parts of the body. A person can be affected by Noonan syndrome in various ways. These include unusual facial characteristics, short stature, heart defects, other physical problems and possible developmental delays.
Noonan syndrome is caused by a genetic mutation and is acquired when a child inherits a copy of an affected gene from a parent (dominant inheritance). It can also occur as a spontaneous mutation, meaning there's no family history involved.
There's no specific treatment for Noonan syndrome. Management focuses on controlling the disease's symptoms and complications. Growth hormone may be used to treat short stature in some people with Noonan syndrome.
The growth spurt that's usually seen during adolescence may be delayed in your child, but because this disease causes bone maturity to be delayed, your child has the potential to continue growing into his or her late teens.
By adulthood, about one-third of people with Noonan syndrome have normal height, but short stature remains more common.
Special education in school may be necessary for some people with Noonan syndrome. Still, it's usual for people with Noonan syndrome to finish high school, go on to college and have careers.
Problems with the eye muscles (strabismus, or crossed eyes), refractive problems — astigmatism, nearsightedness (myopia), farsightedness (hypermetropia), rapid movement of the eyeballs (nystagmus) — and problems with the nerves of the eyes are common.
Genital and kidney conditions
Puberty may be delayed in both boys and girls, but most females develop normal fertility. In males, however, fertility may not develop normally — often because of undescended testicles, a condition that's common in males with Noonan syndrome.
When to see a doctor
The cause of Noonan syndrome is a mutation in a particular gene. Currently, scientists know of eight genes that can cause Noonan syndrome.
The mutation can be inherited from a parent who carries the defective gene (autosomal dominant), or it can develop because of a new mutation in children who don't have a genetic predisposition for the disease. Children who have one parent with Noonan syndrome have a 50 percent chance of developing the disorder.
Defects in these genes cause them to produce proteins that are continually active. Because these genes play a role in the formation of many tissues throughout the body, this constant activation of their proteins disrupts the normal process of cell growth and division.
Autosomal dominant inheritance pattern
In an autosomal dominant disorder, the mutated gene is a dominant gene located on one of the nonsex chromosomes (autosomes). You need only one mutated gene to be affected by this type of disorder. A ...
Many of the symptoms associated with Noonan syndrome are treated just as they would be for anyone else experiencing a health problem. Taken together though, the many problems this disorder can cause require coordinated management by your health care team.
Complications can arise that may require special attention, including:
Preparing for your appointment
If it's suspected that you or your child has Noonan syndrome, you're likely to start by seeing your primary care doctor or your child's pediatrician. However, depending on the signs and symptoms, you or your child may be referred to a specialist. For example, if you or your child has signs and symptoms of heart disease, you'll likely be referred to a cardiologist or a pediatric cardiologist.
Because appointments can be brief, and because there's often a lot of ground to cover, it's a good idea to be well prepared. Here's some information to help you get ready, and what to expect from your doctor.
What you can do
Your time with the doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For Noonan syndrome, some basic questions to ask your doctor include:
What to expect from your doctor
Tests and diagnosis
A diagnosis of Noonan syndrome is usually made after a doctor observes some of the key signs of the disease, but this can be difficult because some of the features associated with this disorder are subtle and can be hard to identify. Sometimes, Noonan syndrome isn't diagnosed until adulthood, only after a person has a child who is more obviously affected by the condition. Molecular genetic testing may help make a diagnosis.
If there's evidence of heart problems, your doctor will likely recommend an:
These tests can be used to assess the type and severity of the condition. These tests are usually done by a doctor who specializes in heart conditions (cardiologist).
Treatments and drugs
Treatment of the symptoms and complications that occur with Noonan syndrome depends on their type and severity. Many of the health and physical issues associated with this syndrome are treated just the way they are in the general population.
The treatment approach that your doctor may recommend to address various aspects of Noonan syndrome may include:
Coping and support
A number of support groups are available for people with Noonan syndrome and their families. Talk to your doctor about finding a support group in your area.
There are also good resources on the Internet that can direct you to local support groups and sources of information about this syndrome.
If you have a family history of Noonan syndrome, talk to your doctor about undergoing genetic counseling before you have children. However, because many of the cases of this disease occur spontaneously, there's often no known way to prevent it.
If Noonan syndrome is detected early, it's possible that ongoing and comprehensive care may lessen some of its complications, such as heart disease.
Last Updated: 2013-08-03
© 1998-2016 Mayo Foundation for Medical Education and Research (MFMER). All rights reserved. A single copy of these materials may be reprinted for noncommercial personal use only. "Mayo," "Mayo Clinic," "MayoClinic.com," "Mayo Clinic Health Information," "Reliable information for a healthier life" and the triple-shield Mayo logo are trademarks of Mayo Foundation for Medical Education and Research.
Terms and conditions of use