Noonan syndrome
Noonan syndrome is a genetic condition that can affect your child in many ways. While some children born with this condition have mild symptoms, others can have more issues.
Symptoms typically include unusual facial features such as a tall forehead and wide-set eyes, lower-set ears and a shorter neck. Many children born with Noonan syndrome also have short stature (short height compared to those the same age), eye issues, low muscle tone and congenital (from birth) heart disease.
While Noonan syndrome has no cure, your healthcare provider can recommend guidance to keep your child as healthy as possible. Your provider will also work closely with you to help prevent complications or catch them early, so your child can lead a full, active life.
Who gets Noonan syndrome?
Anyone can be born with Noonan syndrome. About 50% of people with Noonan syndrome have a parent with the condition. In most cases, a person with Noonan syndrome has a 50% chance of passing the condition on to their child.
Symptoms of Noonan syndrome vary from mild to life-threatening, depending on the affected part of your child’s body. Most symptoms start when the fetus is developing in the uterus or appear in children before age 11.
Facial features of children with Noonan syndrome often become less noticeable as children get older. They may include:
- Tall forehead.
- A deep groove in the middle of their upper lip.
- Drooping eyelid (ptosis).
- A flat nose with a wide base and bulbous (bulging) tip.
- Low-set ears.
- Pale blue or green eye color.
- Wide-set, downward-slanting eyes that may cross (strabismus).
Other common physical symptoms are:
- Bulging toes or finger pads.
- Nails that are abnormally shaped or discolored.
- Short neck with low hairline or extra folds of skin (webbing).
- Short stature.
- Sunken chest (pectus excavatum) or raised sternum (pectus carinatum).
Many children born with Noonan syndrome have heart disorders (congenital heart disease). They may require immediate treatment or develop symptoms later in life. Heart conditions include:
- Atrial septal defect.
- Hypertrophic cardiomyopathy (thickening of the heart muscle).
- Pulmonary artery stenosis.
Noonan syndrome may also cause:
- Breathing issues, such as laryngomalacia.
- A buildup of fluid in the hands or feet (lymphedema).
- Developmental delays.
- Excessive bleeding or bruising.
- Feeding difficulties (in infants).
- Testicles that don’t drop (undescended testicles), which can cause fertility issues if not treated.
- A curved spine (scoliosis).
- Vision problems or hearing loss.
- Birth disorders involving the kidneys.
Noonan syndrome occurs most often due to changes (mutations) in certain genes that help your body’s tissues grow and develop. These mutated genes produce proteins that are active longer than they should be. They interfere with proper cell growth and division.
Noonan syndrome may be:
- Inherited: One parent passes the condition to a child.
- Spontaneous mutation: It develops without any family history.
Genetic testing can find an abnormality in almost 80% of people with Noonan syndrome. For the rest, researchers don’t know the exact cause.
Noonan syndrome belongs to a group of related conditions known as RASopathies (raz-OHP-uh-thees). All of the conditions are due to the same type of abnormal cell growth and development and have similar symptoms.
RASopathies include:
- Cardiofaciocutaneous syndrome.
- Costello syndrome.
- Neurofibromatosis type 1 (NF1).
- Legius syndrome.
- Noonan syndrome with multiple lentigines (formerly, LEOPARD syndrome).
- Turner syndrome.
What other complications are associated with Noonan syndrome?
Many children with Noonan syndrome experience slower-than-usual growth in adolescence, although they may be born at a typical length. About 25% have a learning disability, with only some children having an intellectual disability. Around 10% to 15% of children with Noonan syndrome need special education. Noonan syndrome can also cause developmental delays, behavioral issues or speech disorders.
Some children with Noonan syndrome have an increased chance of an unusual childhood leukemia called juvenile myelomonocytic leukemia (JMML) or other childhood cancers. But the overall risk by age 20 is thought to be around 4%.
Your healthcare provider may suspect Noonan syndrome after a physical exam and review of your child’s symptoms. Your provider may order genetic tests to confirm a diagnosis and rule out other conditions.
Tests may include:
- Complete blood count (CBC).
- Chest X-ray.
- CT scan.
- Echocardiogram.
- Electrocardiogram (EKG).
- Genetic tests.
- Ultrasound.
Your child’s healthcare team develops a treatment plan for Noonan syndrome based on your child’s symptoms and their severity. Your child may receive:
- Assistive devices such as eyeglasses or hearing aids.
- Behavior or speech therapy.
- Educational support for learning disabilities.
- Medication to ease problems with your child’s heart, treat bleeding or improve slowed growth.
- Growth hormone therapy.
- Supportive therapies, such as compression therapy for lymphedema.
In some cases, your healthcare provider may recommend surgery. Early diagnosis is important for effective treatment and follow-up care.
Who might be on my child’s treatment team for Noonan syndrome?
Your team may include your pediatrician and a:
- Vascular medicine specialist (blood vessel expert).
- Neurologist (brain, spinal cord and nerves expert).
- Oncologist (cancer specialist).
- Ophthalmologist (eye care specialist).
- Geneticist (genetics expert).
- Cardiologist (heart and blood vessel specialist).
- Endocrinologist (hormone specialist).
- Nephrologist (kidney specialist).
- Dermatologist (skin, hair and nails specialist).
Your care team will recommend a treatment that’s right for your child. They’ll monitor and adjust medications or therapies based on your child’s condition and any side effects they’re having.
Most people who have Noonan syndrome lead healthy, independent lives. Your child’s care team will work with you to manage your child’s symptoms and prevent complications.
Nothing you do can reduce your child’s risk of developing Noonan syndrome. It happens because of a genetic change. If Noonan syndrome runs in your family, you can talk to your healthcare provider about prenatal genetic testing.
When should I seek care for Noonan syndrome?
When Noonan syndrome causes severe congenital heart disease, your child may require surgery and ongoing monitoring to stay healthy and safe. Your healthcare provider can discuss immediate and long-term treatment options with you.
References
- Carcavilla A, Suárez-Ortega L, Rodríguez Sánchez A, et al. Síndrome de Noonan: actualización genética, clínica y de opciones terapéuticas (https://pubmed.ncbi.nlm.nih.gov/32493603/). [Noonan syndrome: genetic and clinical update and treatment options (https://www.sciencedirect.com/science/article/pii/S2341287920300909)]. An Pediatr (Engl Ed). 2020;93(1):61.e1-61.e14. Accessed 1/27/2023.
- Miller BS. The History of Noonan Syndrome (https://pubmed.ncbi.nlm.nih.gov/31115193/). Pediatr Endocrinol Rev. 2019;16(Suppl 2):424-427. Accessed 1/27/2023.
- National Library of Medicine. Noonan syndrome (https://medlineplus.gov/genetics/condition/noonan-syndrome). Accessed 1/27/2023.
- NHS. Overview: Noonan syndrome (https://www.nhs.uk/conditions/noonan-syndrome/). Accessed 1/27/2023.
- NIH. Genetic and Rare Diseases Information Center. Noonan Syndrome (https://rarediseases.info.nih.gov/diseases/10955/noonan-syndrome). Accessed 1/27/2023.
- NIH. National Human Genome Research Institute. About Noonan Syndrome (https://www.genome.gov/Genetic-Disorders/Noonan-Syndrome). Accessed 1/27/2023.
- Noonan Syndrome Foundation. General Information (https://www.teamnoonan.org/general-information). Accessed 1/27/2023.
- Roberts AE. Noonan Syndrome (https://www.ncbi.nlm.nih.gov/books/NBK1124/). 2022 Feb 17. In: Adam MP, Everman DB, Mirzaa GM, et al., eds. GeneReviews® [Internet]. Seattle, WA: University of Washington, Seattle; 1993-2023. Accessed 1/27/2023.
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