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Noonan syndrome

Last reviewed: 8 Apr 2025
Last updated: 10 Dec 2024

Summary

Definition

History and exam

Key diagnostic factors

  • positive family history
  • short stature
  • dysmorphic facial features
  • cryptorchidism
  • cardiac anomalies
  • delayed puberty
  • easy bruising or bleeding
  • lymphedema
  • pigmentary anomalies
  • sparse or absent eyebrows and lashes
  • splenomegaly
Full details

Other diagnostic factors

  • abnormalities identified prenatally
  • chest deformity
  • developmental delay/learning difficulty
  • skeletal anomalies
  • muscle weakness
  • history of renal malformation
Full details

Risk factors

  • family history of NS
  • advanced paternal age
Full details

Diagnostic tests

1st tests to order

  • ECG
  • echocardiogram
Full details

Tests to consider

  • CBC
  • coagulation profile
  • molecular genetic testing
  • abdominal ultrasound
  • renal ultrasound
Full details

Treatment algorithm

ACUTE

all patients

Contributors

Authors

David A. Stevenson, MD

Associate Professor

Department of Pediatrics

Division of Medical Genetics

Stanford University

Stanford

CA

Disclosures

DAS has acted as a consultant for Lineagen, GLG, and Alexion, and has given expert testimony. He is on the medical advisory board for parents' support groups for Costello syndrome and CFC syndrome. DAS is an author of a reference cited in this topic. DAS has also been reimbursed by RASopathies Network for attending conferences.

Acknowledgements

Dr David A. Stevenson would like to gratefully acknowledge Dr Judith E. Allanson, the previous contributor to this topic. JEA is an author of a number of references cited in this topic.

Peer reviewers

Liliana N. Contreras, MD

Chief

Endocrine Research Department

Instituto de Investigaciones Médicas Alfredo Lanari

IDIM-CONICET

University of Buenos Aires

Argentina

Disclosures

LNC declares that she has no competing interests.

Bruce Gelb, MD

Professor of Pediatrics

Mount Sinai School of Medicine

New York

NY

Disclosures

BG received royalties from GeneDx, Correlegan, Preventative Genetics, Baylor College of Medicine, and Harvard Medical School/Partners for genetic testing of Noonan syndrome. BG is an author of a number of references cited in this topic.

Jacqueline Noonan, MD

Professor Emeriti

Department of Pediatrics

College of Medicine

University of Kentucky

Lexington

KY

Disclosures

JN is on the Noonan Syndrome Advisory Board for Novo Nordisk and has received payment for speaking at a symposium. JN is an author of a number of references cited in this topic.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Jorge AA, Malaquias AC, Arnhold IJ, et al. Noonan syndrome and related disorders: a review of clinical features and mutations in genes of the RAS/MAPK pathway. Horm Res. 2009;71(4):185-93.Full text  Abstract

Shaw AC, Kalidas K, Crosby AH, et al. The natural history of Noonan syndrome: a long-term follow-up study. Arch Dis Child. 2007 Feb;92(2):128-32.Full text  Abstract

Allanson JE. Noonan syndrome. J Med Genet. 1987 Jan;24(1):9-13.Full text  Abstract

Lee DA, Portnoy S, Hill P, et al. Psychological profile of children with Noonan syndrome. Dev Med Child Neurol. 2005 Jan;47(1):35-8. Abstract

Ishizawa A, Oho S, Dodo H, et al. Cardiovascular abnormalities in Noonan syndrome: the clinical findings and treatments. Acta Paediatr Jpn. 1996 Feb;38(1):84-90. Abstract

Romano AA, Allanson JE, Dahlgren J, et al. Noonan syndrome: clinical features, diagnosis, and management guidelines. Pediatrics. 2010 Oct;126(4):746-59. Abstract

Raaijmakers R, Noordam C, Karagiannis G, et al. Response to growth hormone treatment and final height in Noonan syndrome in a large cohort of patients in the KIGS database. J Pediatr Endocrinol Metab. 2008 Mar;21(3):267-73. Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

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