Last reviewed: 16 Sep 2021
Last updated: 14 Oct 2021

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

Other diagnostic factors

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

Risk factors

  • family history of NS
  • advanced paternal age

Diagnostic investigations

Investigations to consider

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

Treatment algorithm

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.

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