Noonan Syndrome 

  • Author: Jennifer Ibrahim, MD; Chief Editor: Bruce Buehler, MD   more...
 
Updated: Aug 24, 2011
 

Background

Noonan syndrome was first recognized as a unique entity in 1963 when Noonan and Ehmke described a series of patients with unusual facies and multiple malformations, including congenital heart disease. These patients were previously thought to have a form of Turner syndrome, with which Noonan syndrome shares numerous clinical features. The observation that patients with Noonan syndrome have normal karyotypes was important in allowing the distinction to be made between the Turner and Noonan syndromes.

The cardinal features of Noonan syndrome include unusual facies (ie, hypertelorism, down-slanting eyes, webbed neck), congenital heart disease (in 50%), short stature, and chest deformity. Approximately 25% of individuals with Noonan syndrome have mental retardation. Bleeding diathesis is present in as many as half of all patients with Noonan syndrome. Skeletal, neurologic, genitourinary, lymphatic, eye, and skin findings may be present to varying degrees.

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Pathophysiology

The pathophysiology of Noonan syndrome is not fully understood. Four disease-causing genes (PTPN11, SOS1, RAF1, and KRAS) have been identified. All 4 genes are part of the RAS/RAF/MEK/ERK signal transduction pathway, which is an important regulator of cell growth. Mutations in the RAS-MAPK signaling pathway are responsible for Noonan syndrome.[1]

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Epidemiology

Frequency

United States

The incidence of Noonan syndrome is estimated to be 1 case per 1000 to 1 case per 2500 live births.

International

The incidence of Noonan syndrome appears to be consistent worldwide.

Mortality/Morbidity

The primary source of morbidity and mortality in these patients depends on the presence and type of congenital heart disease.

Race

Noonan syndrome is panethnic.

Sex

Noonan syndrome occurs in either a sporadic or autosomal dominant fashion. In either case, males and females are equally affected.

Age

The disorder is present from birth, but age impacts the facial phenotype. Infants with Noonan syndrome can be difficult to recognize by facial appearance alone. The phenotype becomes more striking in early childhood, but with advancing age, it may again become quite subtle. Careful examination of an affected child's parents may in fact reveal that they are mildly affected.

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Contributor Information and Disclosures
Author

Jennifer Ibrahim, MD  Chief, Genetics Division, St Joseph's Children's Hospital

Jennifer Ibrahim, MD is a member of the following medical societies: American Society of Human Genetics

Disclosure: Nothing to disclose.

Coauthor(s)

Margaret M McGovern, MD, PhD  Professor and Chair of Pediatrics, Stony Brook University, New York

Margaret M McGovern, MD, PhD is a member of the following medical societies: American Academy of Pediatrics and American Society of Human Genetics

Disclosure: Genzyme Grant/research funds PI

Specialty Editor Board

Elaine H Zackai, MD  Professor of Pediatrics, Professor of Obstetrics and Gynecology, Professor of Pediatrics in Human Genetics, University of Pennsylvania School of Medicine; Director, Clinical Genetics Center, University of Pennsylvania; Senior Physician and Director of Clinical Genetics, The Children's Hospital of Philadelphia

Elaine H Zackai, MD is a member of the following medical societies: American Cleft Palate/Craniofacial Association, American College of Medical Genetics, and American Society of Human Genetics

Disclosure: Nothing to disclose.

Mary L Windle, PharmD  Adjunct Associate Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Nothing to disclose.

Robert Anthony Saul, MD  Clinical Professor, Department of Pediatrics, University of South Carolina School of Medicine; Senior Clinical Geneticist, Greenwood Genetic Center

Robert Anthony Saul, MD is a member of the following medical societies: American Academy of Pediatrics, American College of Medical Genetics, and American College of Physician Executives

Disclosure: Nothing to disclose.

Daniel Rauch, MD, FAAP  Director, Pediatric Hospitalist Program, Associate Professor, Department of Pediatrics, New York University School of Medicine

Daniel Rauch, MD, FAAP is a member of the following medical societies: Ambulatory Pediatric Association, American Academy of Pediatrics, and Society of Hospital Medicine

Disclosure: Baxter Honoraria Consulting

Chief Editor

Bruce Buehler, MD  Professor, Department of Pediatrics and Genetics, Director RSA, University of Nebraska Medical Center

Bruce Buehler, MD is a member of the following medical societies: American Academy for Cerebral Palsy and Developmental Medicine, American Academy of Pediatrics, American Association on Mental Retardation, American College of Medical Genetics, American College of Physician Executives, American Medical Association, and Nebraska Medical Association

Disclosure: Nothing to disclose.

References

  1. Zenker M. Genetic and pathogenetic aspects of Noonan syndrome and related disorders. Horm Res. Dec 2009;72 Suppl 2:57-63. [Medline].

  2. Tartaglia M, Kalidas K, Shaw A, et al. PTPN11 mutations in Noonan syndrome: molecular spectrum, genotype-phenotype correlation, and phenotypic heterogeneity. Am J Hum Genet. Jun 2002;70(6):1555-63. [Medline].

  3. Tartaglia M, Pennacchio LA, Zhao C, et al. Gain-of-function SOS1 mutations cause a distinctive form of Noonan syndrome. Nat Genet. Jan 2007;39(1):75-9. [Medline].

  4. Pandit B, Sarkozy A, Pennacchio LA, et al. Gain-of-function RAF1 mutations cause Noonan and LEOPARD syndromes with hypertrophic cardiomyopathy. Nat Genet. Aug 2007;39(8):1007-12. [Medline].

  5. Schubbert S, Zenker M, Rowe SL, et al. Germline KRAS mutations cause Noonan syndrome. Nat Genet. Mar 2006;38(3):331-6. [Medline].

  6. Carta C, Pantaleoni F, Bocchinfuso G, et al. Germline missense mutations affecting KRAS Isoform B are associated with a severe Noonan syndrome phenotype. Am J Hum Genet. Jul 2006;79(1):129-35. [Medline].

  7. Pierpont EI, Pierpont ME, Mendelsohn NJ, Roberts AE, Tworog-Dube E, Seidenberg MS. Genotype differences in cognitive functioning in Noonan syndrome. Genes Brain Behav. Apr 2009;8(3):275-82. [Medline].

  8. Romano AA, Dana K, Bakker B, et al. Growth Response, Near-Adult Height, and Patterns of Growth and Puberty in Patients With Noonan Syndrome Treated With Growth Hormone. J Clin Endocrinol Metab. Apr 28 2009;[Medline].

  9. Binder G. Noonan syndrome, the Ras-MAPK signalling pathway and short stature. Horm Res. Apr 2009;71 Suppl 2:64-70. [Medline].

  10. Houweling AC, de Mooij YM, van der Burgt I, et al. Prenatal detection of Noonan syndrome by mutation analysis of the PTPN11 and the KRAS genes. Prenat Diagn. Mar 2010;30(3):284-6. [Medline].

  11. Jongmans MC, van der Burgt I, Hoogerbrugge PM, et al. Cancer risk in patients with Noonan syndrome carrying a PTPN11 mutation. Eur J Hum Genet. Aug 2011;19(8):870-4. [Medline].

  12. Allanson JE. Noonan syndrome. J Med Genet. Jan 1987;DA - 19870320(1):9-13. [Medline].

  13. Allanson JE, Hall JG, Hughes HE, et al. Noonan syndrome: the changing phenotype. Am J Med Genet. Jul 1985;21(3):507-14. [Medline].

  14. Aoki Y, Niihori T, Narumi Y, Kure S, Matsubara Y. The RAS/MAPK syndromes: novel roles of the RAS pathway in human genetic disorders. Hum Mutat. Aug 2008;29(8):992-1006. [Medline].

  15. Bader-Meunier B, Tchernia G, Mielot F, et al. Occurrence of myeloproliferative disorder in patients with Noonan syndrome. J Pediatr. Jun 1997;130(6):885-9. [Medline].

  16. Ferrero GB, Baldassarre G, Delmonaco AG, Biamino E, Banaudi E, Carta C, et al. Clinical and molecular characterization of 40 patients with Noonan syndrome. Eur J Med Genet. Nov-Dec 2008;51(6):566-72. [Medline].

  17. Marino B, Digilio MC, Toscano A, et al. Congenital heart diseases in children with Noonan syndrome: An expanded cardiac spectrum with high prevalence of atrioventricular canal. J Pediatr. Dec 1999;135(6):703-6. [Medline].

  18. Noonan JA. Hypertelorism with Turner phenotype. A new syndrome with associated congenital heart disease. Am J Dis Child. Oct 1968;116(4):373-80. [Medline].

  19. Noonan JA. Noonan syndrome revisited. J Pediatr. Dec 1999;135(6):667-8. [Medline].

  20. Noonan JA. Noonan syndrome. An update and review for the primary pediatrician. Clin Pediatr (Phila). Sep 1994;33(9):548-55. [Medline].

  21. Qiu WW, Yin SS, Stucker FJ. Audiologic manifestations of Noonan syndrome. Otolaryngol Head Neck Surg. Mar 1998;118(3 Pt 1):319-23. [Medline].

  22. Sharland M, Burch M, McKenna WM, Paton MA. A clinical study of Noonan syndrome. Arch Dis Child. Feb 1992;67(2):178-83. [Medline].

  23. Sharland M, Morgan M, Smith G, et al. Genetic counseling in Noonan syndrome. Am J Med Genet. Feb 15 1993;45(4):437-40. [Medline].

  24. Singer ST, Hurst D, Addiego JE Jr. Bleeding disorders in Noonan syndrome: three case reports and review of the literature. J Pediatr Hematol Oncol. Mar-Apr 1997;19(2):130-4. [Medline].

  25. van der Burgt I, Thoonen G, Roosenboom N, et al. Patterns of cognitive functioning in school-aged children with Noonan syndrome associated with variability in phenotypic expression. J Pediatr. Dec 1999;135(6):707-13. [Medline].

 
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Lymphedema of the feet in an infant is shown. The toes have the characteristic sausagelike appearance.
Generalized lymphedema is seen here in an infant. The loose skin folds around the neck will form a webbed neck later in life.
 
 
 
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