About Noonan Syndrome
Noonan syndrome (NS) is an autosomal dominant disorder caused by mutations in genes regulating the RAS/MAPK signaling pathway (PTPN11 accounting for ~50% of cases, SOS1, RAF1, RIT1, BRAF, KRAS, and others), making it a primary RASopathy.
The condition is characterized by distinctive craniofacial features including hypertelorism (widely spaced eyes), short philtrum, micrognathia (small jaw), and low-set, posteriorly rotated ears. Short stature affects about 50 to 70% of patients, who are usually a normal size at birth and grow more slowly over time; response to growth hormone varies. Cardiac involvement (~80% of patients) includes pulmonary stenosis (most common), hypertrophic cardiomyopathy, atrial septal defect, and aortic stenosis. Developmental delays and learning disabilities occur in 25-75% of patients depending on the causative gene and mutation severity.
Hematologic abnormalities including platelet dysfunction, bleeding tendency, and elevated INR occur in ~50%. Increased cancer predisposition, particularly childhood leukemia and certain solid tumors, requires ongoing surveillance. Prognosis is generally good with appropriate multidisciplinary care; life expectancy is near-normal.
Common Symptoms of Noonan Syndrome
Recognizing the signs of Noonan Syndrome early can lead to faster diagnosis and better outcomes. Symptoms may vary in severity from person to person. If you or a loved one are experiencing any of the following, consider speaking with a specialist.
- Characteristic facial features (hypertelorism, low-set ears, micrognathia)
- Short stature
- Cardiac defects (pulmonary stenosis, hypertrophic cardiomyopathy)
- Developmental and learning delays
- Bleeding tendency and platelet dysfunction
- Increased cancer predisposition (particularly leukemia)
Who Noonan Syndrome Affects
NS shows autosomal dominant inheritance. A causative gene change is found in about 80 to 85% of patients, and the cause is still unknown in 15 to 20%. The condition affects males and females equally. Approximately 50% of cases are inherited from an affected parent (vertical transmission), while approximately 50% represent new (de novo) mutations. Penetrance is high but variable expressivity is notable, even within the same family.
Geographic and ethnic distribution is worldwide with no significant population predilection. Advanced paternal age increases risk of de novo mutations, particularly PTPN11 mutations. Recurrence risk for offspring of affected individuals is 50% per pregnancy (assuming single-gene inheritance).
Find Your Next Step
FDA-Approved Treatments for Noonan Syndrome
There are currently 2 FDA-approved medications for Noonan Syndrome. These therapies represent the current standard of care and may be used alongside or compared against investigational treatments in active clinical trials.
Source: openFDA drug labeling data. This list may not include all treatments. Always consult your doctor.
Side Effect Explorer
Real-world side effect reports from the FDA Adverse Event Reporting System (FAERS). Includes both FDA-approved drugs and investigational therapies from active clinical trials. Click any drug to see what patients reported.
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Genetic Testing
Genetic testing can confirm a diagnosis, guide treatment decisions, and identify family members who may be at risk.
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Trusted Noonan Syndrome Resources
Reputable organizations and medical references for learning more about Noonan Syndrome, including disease registries, foundation resources, and clinical guidelines.