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Noonan Syndrome

Abstract

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NORD is very grateful to Amy E. Roberts, MD, Assistant Professor of Medicine, Harvard Medical School and Cardiovascular Genetics, Division of Genetics and Department of Cardiology, Boston Children's Hospital and Judith Allanson, MD, Chief of Department of Genetics, Children's Hospital of Eastern Ontario, Ottawa and Professor of Pediatrics, University of Ottawa, for assistance in the preparation of this report.

Synonyms of Noonan Syndrome

  • female pseudo-Turner syndrome
  • male Turner syndrome
  • NS
  • Turner phenotype with normal chromosomes (karyotype)

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Noonan syndrome is a common genetic disorder that is typically evident at birth (congenital). The disorder is characterized by a wide spectrum of symptoms and physical features that vary greatly in range and severity. In many affected individuals, associated abnormalities include a distinctive facial appearance; a broad or webbed neck; a low posterior hairline; a typical chest deformity and short stature. Characteristic abnormalities of the head and facial (craniofacial) area may include widely set eyes (ocular hypertelorism); skin folds that may cover the eyes' inner corners (epicanthal folds); drooping of the upper eyelids (ptosis); a small jaw (micrognathia); a depressed nasal root; a short nose with broad base; and low-set, posteriorly rotated ears (pinnae). Distinctive skeletal malformations are also typically present, such as abnormalities of the breastbone (sternum), curvature of the spine (kyphosis and/or scoliosis), and outward deviation of the elbows (cubitus valgus). Many infants with Noonan syndrome also have heart (cardiac) defects, such as obstruction of proper blood flow from the lower right chamber of the heart to the lungs (pulmonary valvular stenosis) and hypertrophic cardiomyopathy. Additional abnormalities may include malformations of certain blood and lymph vessels, blood clotting and platelet deficiencies, learning difficulties or mild intellectual disability, failure of the testes to descend into the scrotum (cryptorchidism) by the first year of life in affected males, and/or other symptoms and findings.

Noonan syndrome is an autosomal dominant genetic disorder caused by abnormalities (mutations) in four main genes: PTPN11 (50%), SOS1 (13%), RAF1 (3-17%), KRAS (less than 5%), with a handful of individuals having a mutation in NRAS, BRAF or MEK2. Noonan-like disorders are found in association with mutations in SHOC2 and CBL.

Organizations related to Noonan Syndrome

Please note that some of these organizations may provide information concerning certain conditions potentially associated with this disorder.

The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

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