Skip to content
Inciteful Med

Recognizing the Signs: Symptoms of Noonan Syndrome

Last updated:

Noonan syndrome is a multisystem genetic disorder defined by a clinical triad: distinctive facial features, heart defects, and short stature. Other common symptoms include infant feeding difficulties, easy bruising, skeletal changes, and learning delays.

Key Takeaways

  • • The primary clinical triad of Noonan syndrome includes distinctive facial features, heart defects, and short stature.
  • • Approximately 80% of individuals with Noonan syndrome have heart conditions, most commonly pulmonary valve stenosis or hypertrophic cardiomyopathy.
  • • Severe feeding difficulties are common in the first year of life but typically improve as children grow.
  • • About half of people with Noonan syndrome have a bleeding disorder, making medical screening essential before surgeries or dental procedures.
  • • Symptoms are highly variable and can change over time, requiring lifelong monitoring by a team of medical specialists.

Noonan syndrome (NS) is often described as a “multisystem” disorder because its effects can be seen in many different parts of the body [1]. While every person with NS is unique, doctors typically look for a “triad” of three main categories of symptoms when making a diagnosis [2][3].

The Clinical Triad

The three most common features that define Noonan syndrome include:

  1. Distinctive Facial Features: These are often most noticeable in early childhood and may include widely spaced eyes (hypertelorism), drooping eyelids (ptosis), ears that are set lower on the head or rotated backward, and a broad or webbed neck [2][4][5]. As children grow into adulthood, these features often become much more subtle [6][7].
  2. Heart Defects: Approximately 80% of individuals with NS have a heart-related finding [8]. The most frequent are pulmonary valve stenosis (a narrowing of the valve that allows blood to flow from the heart to the lungs) and hypertrophic cardiomyopathy (a thickening of the heart muscle) [9][10][11].
  3. Growth and Stature: Most children with NS grow more slowly than their peers [12][13]. Without treatment, many will be significantly shorter than the average adult, though specialized growth charts and growth hormone therapy can help manage this [14][13].

Beyond the Triad: Other Common Features

Noonan syndrome can involve several other systems that are sometimes overlooked:

  • Feeding Difficulties: Severe feeding issues and “failure to thrive” in the first year of life are incredibly common in Noonan syndrome and are often a primary source of severe stress for new parents. These usually improve as the child grows [2].
  • Skeletal Changes: Many individuals have a chest that is shaped differently, such as a sunken chest (pectus excavatum) or a protruding chest (pectus carinatum) [15][2].
  • Bleeding and Bruising: About half of people with NS have a “bleeding diathesis,” which means their blood does not clot as easily as it should [16][17]. This can lead to easy bruising or frequent nosebleeds and is very important for doctors to know before any surgery [16].
  • Lymphatic Issues: The lymphatic system (which helps manage fluid in the body) may not develop correctly [18][17]. This can cause swelling in the legs or feet (lymphedema) or, more rarely, fluid buildup around the lungs (chylothorax) [17][19].
  • Neurodevelopmental Challenges: Learning and behavior can also be affected. ADHD is common (affecting about 30-40%), and some individuals may have autism spectrum disorder (ASD) or mild learning delays [20][21][22].

Variability and Progression

It is important to understand that Noonan syndrome is variable [23]. One child might have a significant heart defect but typical growth, while another may have short stature and mild learning delays but a perfectly healthy heart [24].

Symptoms also change over time. Facial features tend to soften with age, while heart conditions like hypertrophic cardiomyopathy can sometimes be progressive, meaning they may develop or change as a child grows [10][25]. Regular check-ups with a coordinated team of specialists are essential to monitor these changes throughout life [26][27].

Return to Home Page

Frequently Asked Questions

What are the main symptoms of Noonan syndrome?
Doctors typically look for a classic 'triad' of signs to diagnose Noonan syndrome. This includes distinctive facial features, congenital heart defects, and slower growth resulting in short stature.
Will Noonan syndrome symptoms change as my child grows?
Yes, symptoms often evolve. Distinctive facial features tend to soften and become more subtle in adulthood, while certain heart conditions like hypertrophic cardiomyopathy may develop or progress over time.
Are bleeding and bruising common in Noonan syndrome?
About half of people with Noonan syndrome have a bleeding disorder that prevents their blood from clotting easily. This can cause frequent nosebleeds or easy bruising, and requires special testing before any dental work or surgeries.
Why do babies with Noonan syndrome have trouble eating?
Severe feeding issues and 'failure to thrive' are very common in the first year of life, which can be highly stressful for parents. Fortunately, these feeding difficulties typically improve on their own as the child grows.
Can Noonan syndrome affect learning and behavior?
Yes, the condition can affect neurodevelopment. Attention-deficit/hyperactivity disorder (ADHD) affects about 30-40% of individuals, and some may also experience mild learning delays or autism spectrum disorder.

Questions for Your Doctor

  • • Based on my child's (or my) specific genetic mutation, which symptoms are we most likely to see?
  • • Are the heart findings we have now (like pulmonary stenosis) expected to change or worsen as they get older?
  • • Should we perform a 'bleeding workup' before any upcoming dental or surgical procedures?
  • • Is the current height following the specialized Noonan syndrome growth charts?
  • • What is the best way to monitor for lymphatic issues like swelling (lymphedema)?

Questions for You

  • • Which symptoms am I most concerned about today, and which ones feel manageable?
  • • Have I noticed any subtle issues, like easy bruising or joint pain, that I haven't mentioned to the doctor yet?
  • • How are these symptoms impacting daily life, school, or social activities?
  • • Do I feel like our current care team is addressing all the different aspects (heart, growth, learning) of Noonan syndrome?

Want personalized information?

Type your question below to get evidence-based answers tailored to your situation.

References

  1. 1

    The RASopathies: Biology, genetics and therapeutic options.

    Longo JF, Carroll SL

    Advances in cancer research 2022; (153()):305-341 doi:10.1016/bs.acr.2021.07.007.

    PMID: 35101235
  2. 2

    Noonan syndrome with somnambulism: A rare case report.

    Sahu S, Chaudhury S, Saldanha D

    Industrial psychiatry journal 2020; (29(2)):339-341 doi:10.4103/ipj.ipj_84_19.

    PMID: 34158723
  3. 3

    Noonan syndrome - a new survey.

    Tafazoli A, Eshraghi P, Koleti ZK, Abbaszadegan M

    Archives of medical science : AMS 2017; (13(1)):215-222 doi:10.5114/aoms.2017.64720.

    PMID: 28144274
  4. 4

    Antenatal diagnosis of cardio-facio-cutaneous syndrome: Prenatal characteristics and contribution of fetal facial dysmorphic signs in utero. About a case and review of literature.

    Biard JM, Steenhaut P, Bernard P, et al.

    European journal of obstetrics, gynecology, and reproductive biology 2019; (240()):232-241 doi:10.1016/j.ejogrb.2019.06.035.

    PMID: 31336229
  5. 5

    Loss-of-function variants in ERF are associated with a Noonan syndrome-like phenotype with or without craniosynostosis.

    Dentici ML, Niceta M, Lepri FR, et al.

    European journal of human genetics : EJHG 2024; (32(8)):954-963 doi:10.1038/s41431-024-01642-7.

    PMID: 38824261
  6. 6

    Phenotypic and genotypic spectrum of noonan syndrome: A retrospective analysis of 46 consecutive pediatric patients presented at a regional cardiac center in China.

    Chen Q, Hong D, Huang Y, et al.

    Heliyon 2024; (10(5)):e27038 doi:10.1016/j.heliyon.2024.e27038.

    PMID: 38463782
  7. 7

    Congenital heart defects in Noonan syndrome: Diagnosis, management, and treatment.

    Linglart L, Gelb BD

    American journal of medical genetics. Part C, Seminars in medical genetics 2020; (184(1)):73-80 doi:10.1002/ajmg.c.31765.

    PMID: 32022400
  8. 8

    Juvenile xanthogranuloma in Noonan syndrome.

    Ali MM, Gilliam AE, Ruben BS, et al.

    American journal of medical genetics. Part A 2021; (185(10)):3048-3052 doi:10.1002/ajmg.a.62353.

    PMID: 34032360
  9. 9

    Coronary artery ectasia in Noonan syndrome: Report of an individual with SOS1 mutation and literature review.

    Calcagni G, Baban A, De Luca E, et al.

    American journal of medical genetics. Part A 2016; (170(3)):665-9 doi:10.1002/ajmg.a.37505.

    PMID: 26686981
  10. 10

    Cardiac Manifestations of Noonan Syndrome.

    Karnik R, Geiger M

    Pediatric endocrinology reviews : PER 2019; (16(Suppl 2)):471-476 doi:10.17458/per.vol16.2019.kpg.manifestationsnoonan.

    PMID: 31115199
  11. 11

    Cardiovascular Abnormalities and Gene Mutations in Children With Noonan Syndrome.

    Sun L, Xie YM, Wang SS, Zhang ZW

    Frontiers in genetics 2022; (13()):915129 doi:10.3389/fgene.2022.915129.

    PMID: 35770001
  12. 12

    Noonan syndrome and Noonan-like syndrome with loose anagen hair: rare phenotypes may emerge during follow-up.

    Liu Z, Lai J, Song F

    Translational pediatrics 2024; (13(7)):1161-1168 doi:10.21037/tp-24-113.

    PMID: 39144424
  13. 13

    Case report: A de novo RASopathy-causing SHOC2 variant in a Chinese girl with noonan syndrome-like with loose anagen hair.

    Wang Q, Cheng S, Fu Y, Yuan H

    Frontiers in genetics 2022; (13()):1040124 doi:10.3389/fgene.2022.1040124.

    PMID: 36579329
  14. 14

    Noonan Syndrome Growth Charts and Genotypes: 15-Year Longitudinal Single-Centre Study.

    Cappa M, Cappa M, d'Aniello F, et al.

    Hormone research in paediatrics 2025; (98(6)):655-667 doi:10.1159/000540092.

    PMID: 38964306
  15. 15

    Modified Nuss procedure versus Ravitch in concurrent repair of pectus deformity and open-heart surgery.

    Davari H, Asbagh RA, Hosseini S, et al.

    Asian cardiovascular & thoracic annals 2026; (34(1)):33-42 doi:10.1177/02184923251404220.

    PMID: 41364214
  16. 16

    [Cochlear implantation in a patient with Noonan syndrome caused by a variant in PTPN11: a case report].

    Hu L, Chen J, Xin Y, et al.

    Lin chuang er bi yan hou tou jing wai ke za zhi = Journal of clinical otorhinolaryngology head and neck surgery 2021; (35(9)):839-842 doi:10.13201/j.issn.2096-7993.2021.09.016.

    PMID: 34628841
  17. 17

    Lymphatic anomalies during lifetime in patients with Noonan syndrome: Retrospective cohort study.

    Swarts JW, Kleimeier LER, Leenders EKSM, et al.

    American journal of medical genetics. Part A 2022; (188(11)):3242-3261 doi:10.1002/ajmg.a.62955.

    PMID: 35979676
  18. 18

    Lymphatic Abnormalities in Noonan Syndrome Spectrum Disorders: A Systematic Review.

    Sleutjes J, Kleimeier L, Leenders E, et al.

    Molecular syndromology 2022; (13(1)):1-11 doi:10.1159/000517605.

    PMID: 35221870
  19. 19

    MR lymphangiography of lymphatic abnormalities in children and adults with Noonan syndrome.

    Pieper CC, Wagenpfeil J, Henkel A, et al.

    Scientific reports 2022; (12(1)):11164 doi:10.1038/s41598-022-13806-w.

    PMID: 35778409
  20. 20

    Prevalence of neurodevelopmental and psychiatric disorders in Noonan syndrome: a systematic review and meta-analysis.

    Pascual-Morena C, Martínez-García I, Lucerón-Lucas-Torres M, et al.

    European journal of pediatrics 2025; (184(12)):800 doi:10.1007/s00431-025-06648-x.

    PMID: 41310115
  21. 21

    Neuropsychiatric phenotypes in children with Noonan syndrome.

    Naylor PE, Bruno JL, Shrestha SB, et al.

    Developmental medicine and child neurology 2023; (65(11)):1520-1529 doi:10.1111/dmcn.15627.

    PMID: 37130201
  22. 22

    Psychopathology and Adaptive Functioning in Children, Adolescents, and Young Adults with Noonan Syndrome.

    Davico C, Borgogno M, Campagna F, et al.

    Journal of developmental and behavioral pediatrics : JDBP 2022; (43(2)):e87-e93 doi:10.1097/DBP.0000000000000991.

    PMID: 34269737
  23. 23

    High frequency of hotspot mutation in PTPN11 gene among Moroccan patients with Noonan syndrome.

    Ouboukss F, Adadi N, Amasdl S, et al.

    Journal of applied genetics 2024; (65(2)):303-308 doi:10.1007/s13353-023-00803-6.

    PMID: 37987971
  24. 24

    Spectrum of mutations and genotype-phenotype analysis in Noonan syndrome patients with RIT1 mutations.

    Yaoita M, Niihori T, Mizuno S, et al.

    Human genetics 2016; (135(2)):209-22 doi:10.1007/s00439-015-1627-5.

    PMID: 26714497
  25. 25

    Atypical cardiac defects in patients with RASopathies: Updated data on CARNET study.

    Calcagni G, Gagliostro G, Limongelli G, et al.

    Birth defects research 2020; (112(10)):725-731 doi:10.1002/bdr2.1670.

    PMID: 32558384
  26. 26

    RASopathy in Patients With Isolated Sagittal Synostosis.

    Davis AA, Zuccoli G, Haredy MM, et al.

    Global pediatric health 2019; (6()):2333794X19846774 doi:10.1177/2333794X19846774.

    PMID: 31192281
  27. 27

    A genotype-first approach to exploring Mendelian cardiovascular traits with clear external manifestations.

    Wenger BM, Patel N, Lui M, et al.

    Genetics in medicine : official journal of the American College of Medical Genetics 2021; (23(1)):94-102 doi:10.1038/s41436-020-00973-2.

    PMID: 32989268

This page provides educational information about Noonan syndrome symptoms and characteristics. Always consult your geneticist, pediatrician, or care team for professional medical advice, diagnosis, and monitoring.

Stay up to date

Get notified when new research about Noonan syndrome is published.

No spam. Unsubscribe anytime.