11 Surprising Symptoms Associated With Noonan Syndrome

Noonan syndrome is a genetic condition that affects approximately one in every 1,000 to 2,500 people, yet many remain unaware of its full range of symptoms. While it’s commonly associated with heart defects, short stature, and minor eye issues, this complex disorder can manifest in unexpected ways, impacting multiple systems in the body. Caused by mutations in genes like PTPN11, KRAS, SOS1, and RAF1, Noonan syndrome is present from birth and can be diagnosed through clinical evaluation and genetic testing. However, because its symptoms vary widely in severity and presentation, early recognition is key to managing the condition effectively. To help raise awareness and improve early diagnosis, we’ve expanded our list to highlight 11 surprising symptoms of Noonan syndrome that many people don’t realize are linked to the disorder. From unusual facial features to bleeding disorders and feeding difficulties, these lesser-known signs can offer crucial clues for patients, families, and healthcare providers alike.

1. Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy occurs when the heart muscle thickens, increasing the effort it takes to pump blood throughout the body. Most patients with hypertrophic cardiomyopathy are asymptomatic, and the ailment sometimes goes undetected. In patients who do have symptoms, they include shortness of breath, chest pain, and abnormal heart rhythms (arrhythmias). Shortness of breath and chest pain usually occur after exercise or exertion, and patients may also notice a pounding or fluttering sensation in their chest. A small number of patients might have a heart murmur, and this can be detected when a doctor listens to the heart with a stethoscope. To diagnose hypertrophic cardiomyopathy, clinicians perform a physical exam of the cardiovascular system, and they will also order electrocardiograms (ECG) and echocardiograms. In some cases, patients might be asked to wear a Holter monitor (a portable ECG) for a few days or to undergo a treadmill stress test, cardiac MRI, or cardiac catheterization. To treat hypertrophic cardiomyopathy, doctors begin by prescribing beta blockers or calcium channel blockers to reduce the patient's heart rate and enable the heart to pump more easily. Patients may also be prescribed amiodarone or other medicines to treat arrhythmia. Surgical interventions, including septal ablation and septal myectomy, may be recommended for patients with advanced stages of hypertrophic cardiomyopathy.

2. Pulmonary Valve Stenosis

Pulmonary valve stenosis happens when a deformity of the pulmonary valve causes it to narrow, restricting blood flow. This condition is a common congenital heart defect in Noonan syndrome patients. Symptoms range in severity, and they generally include shortness of breath, chest pain, fainting, heart murmurs, and fatigue. Patients with pulmonary valve stenosis are at an increased risk of endocarditis, arrhythmias, and heart failure. To diagnose this form of stenosis, doctors do a physical exam, and echocardiograms, electrocardiograms, and MRI or CT scans may be needed. Some patients might also need to undergo a cardiac catheterization procedure. If the patient's symptoms are mild, treatment for this ailment may consist solely of regular checkups. For patients with more severe symptoms, balloon valvuloplasty, valve repair, or valve replacement surgeries may be recommended.

3. Distinct Facial Features

Noonan syndrome patients typically have a number of distinct facial features, though these can vary slightly from patient to patient. Some of the most common are drooping eyelids, wide-set eyes with pale irises, a large head size, and a broad forehead. Patients may also have facial droopiness, low-set ears, and a short neck with excess skin. As the patient gets older, the skin may become thinner and more transparent, and their facial features may sharpen. Some patients with Noonan syndrome also have distinctive features in the nose and mouth. The nose may be short and broad, appearing pushed in at the top of the nasal bridge and having a bulbous tip. The patient's upper lip may have wider than usual peaks, and there is often a very deep fold between the edge of the nose and corner of the mouth. The patient's jaw may be quite small, and they might have a highly arched palate. If the patient desires, surgical interventions can be used to alter some of the facial features associated with Noonan syndrome.

4. Delayed Growth

While the birthweight of patients with Noonan syndrome is typically within the normal range, they usually experience delayed growth during childhood. Patients often have inadequate growth hormone levels, and they may experience feeding difficulties, leading to poor nutrition and problems with weight gain. Puberty may be delayed, and the growth spurt generally expected around this time is also often delayed. However, since Noonan syndrome also results in delays with achieving bone maturity, patients may continue growing throughout their late teenage years. Some patients are able to attain normal height by adulthood, and others may remain shorter than their peers. In addition to delayed physical growth, a small percentage of Noonan syndrome patients may experience mild developmental delays as well. Children with this condition can usually attend mainstream school, and they may sometimes need an individualized education plan.

5. Pectus Excavatum Or Carinatum

Pectus excavatum or carinatum may develop for some patients with Noonan syndrome. Pectus excavatum is a sunken chest, and pectus carinatum is a type of chest protrusion called funnel chest. Most patients with pectus excavatum have a mild dent in the chest and experience only minor symptoms, if any. For patients with more severe cases of pectus excavatum, the breastbone tends to compress the heart and lungs. This compression often results in wheezing, coughing, chest pain, fatigue, and a decreased tolerance for exercise. Heart palpitations, a rapid heartbeat, or a heart murmur may also be present. Pectus carinatum causes the chest to jut out, and patients with this condition may experience fatigue, chest pain, rapid heartbeat, and shortness of breath. Both pectus excavatum and pectus carinatum can usually be diagnosed with a physical exam. Patients may also have a chest x-ray, electrocardiogram, and CT or MRI scans to check for internal damage to the heart or lungs. Surgery may be advised for severe cases of pectus excavatum. Patients with pectus carinatum may be offered a chest brace that can push the chest wall back to a normal position. In some cases, surgical procedures such as the Ravitch procedure might be recommended.

6. Unusual Bruising and Bleeding Disorders

People with Noonan syndrome often experience easy bruising and prolonged bleeding, even from minor injuries or routine procedures like dental work. This occurs due to underlying clotting abnormalities, such as platelet dysfunction or deficiencies in clotting factors. In some cases, patients may have von Willebrand disease, a bleeding disorder that affects blood clot formation. Parents might notice frequent nosebleeds, excessive bruising after play, or prolonged bleeding from cuts and scrapes. Women with Noonan syndrome may also experience heavy menstrual bleeding (menorrhagia). Since these clotting abnormalities can pose serious risks during surgery or childbirth, early diagnosis and management—including blood tests and medication—are crucial.

7. Gastrointestinal and Feeding Challenges

Many infants and young children with Noonan syndrome experience significant feeding difficulties, which can lead to failure to thrive in infancy. Issues may include gastroesophageal reflux disease (GERD), difficulty swallowing (dysphagia), poor sucking ability, and delayed progression to solid foods. These challenges can make weight gain difficult and often require medical intervention such as specialized feeding therapy, tube feeding, or medications to manage reflux. Even in older children and adults, gastrointestinal issues like chronic constipation, bloating, and irritable bowel syndrome (IBS)-like symptoms may persist. Addressing these issues with dietary modifications, probiotics, and digestive enzyme support can improve quality of life.

8. Curly or Sparse Hair and Brittle Nails

Noonan syndrome is often associated with distinctive hair and nail changes, which many people don’t immediately recognize as related to the condition. Patients frequently have thin, sparse, or slow-growing hair, which may be curly, coarse, or brittle. Some may experience early hair thinning or hair loss, especially around the temples. Nails are often thin, brittle, or ridged, making them prone to splitting or breaking. These features are thought to be linked to abnormal connective tissue function, which also contributes to loose skin and joint hypermobility in some patients. While these symptoms are not dangerous, they can be frustrating, especially for those struggling with self-image. Nutritional support, gentle hair care routines, and hydration can help improve hair and nail health.

9. Hearing and Speech Delays

Many individuals with Noonan syndrome experience hearing difficulties, including mild to moderate hearing loss. This can result from recurrent ear infections, structural ear abnormalities, or nerve-related (sensorineural) hearing loss. Speech delays are also very common, often due to low muscle tone (hypotonia) affecting the mouth and tongue, as well as hearing challenges. Children may have difficulty forming words, delayed speech milestones, or a distinct nasal or breathy voice quality. Early intervention with speech therapy, hearing aids, or medical treatment for ear infections can significantly improve communication skills and confidence.

10. Joint Hypermobility and Muscular Weakness

Many individuals with Noonan syndrome have loose, hypermobile joints, which can lead to poor coordination, joint pain, and increased risk of sprains and dislocations. This occurs due to abnormal connective tissue function, similar to what’s seen in conditions like Ehlers-Danlos syndrome. Children may exhibit low muscle tone (hypotonia), leading to delays in crawling, walking, or fine motor skills like writing and buttoning clothes. Adults may experience chronic joint pain, stiffness, or fatigue, making physical activities more difficult. Physical therapy, targeted exercises, and supportive braces can help improve strength and prevent long-term complications.

11. Anxiety, Social Difficulties, and Autism-Like Traits

Noonan syndrome is often linked to behavioral and emotional challenges, including increased anxiety, sensory sensitivities, and difficulties with social interaction. Some individuals exhibit traits similar to autism spectrum disorder (ASD), attention-deficit/hyperactivity disorder (ADHD), or obsessive-compulsive tendencies. Children with Noonan syndrome may struggle with processing emotions, engaging in social play, or adapting to changes in routine. Sensory issues—such as sensitivity to noise, textures, or bright lights—are also common. Recognizing these challenges early allows for targeted support, including behavioral therapy, occupational therapy, and school accommodations to help individuals thrive in social and academic settings.

More Than Just a Genetic Condition

Noonan syndrome is far more than just a heart condition or growth disorder—it affects multiple aspects of a person’s life, from hair and nails to digestion, joints, and social interactions. Understanding these lesser-known symptoms can lead to earlier diagnosis, better management, and improved quality of life for individuals living with this condition. If you or a loved one has Noonan syndrome, staying informed and working with a team of specialists—including cardiologists, geneticists, therapists, and nutritionists—can help create a personalized care plan for lifelong health and well-being.