Last reviewed: 16 Apr 2021
Last updated: 29 May 2018



History and exam

Key diagnostic factors

  • positive FHx
  • 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
  • hx of renal malformation

Risk factors

  • FHx of NS
  • advanced paternal age

Diagnostic investigations

Investigations to consider

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

Treatment algorithm


Associate Professor

Department of Pediatrics

Division of Medical Genetics

Stanford University




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 monograph.

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

Peer reviewersVIEW ALL


Endocrine Research Department

Instituto de Investigaciones Médicas Alfredo Lanari


University of Buenos Aires



LNC declares that she has no competing interests.

Professor of Pediatrics

Mount Sinai School of Medicine

New York



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 monograph.

Professor Emeriti

Department of Pediatrics

College of Medicine

University of Kentucky




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 monograph.

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