Noonan Syndrome Workup

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

Laboratory Studies

The following laboratory studies may be indicated in patients with Noonan syndrome:

  • Bleeding diatheses are common among patients with Noonan syndrome. The most frequent abnormality is factor XI deficiency, but various disorders have been reported in patients with Noonan syndrome. A CBC count with platelet count, coagulation profile, and measurement of factor XI level should be obtained at a minimum.
  • If full phenotypic expression is not apparent, karyotyping may be necessary.
  • Mutation analysis may confirm the diagnosis. However, the failure to identify a germline mutation in any of the associated genes does not rule out Noonan syndrome. This entity remains a clinical diagnosis.
  • Many individuals with Noonan syndrome have reduced insulinlike growth factor-1 (IGF-1) and IGF-binding protein 3 but these tests are not diagnostic of the syndrome itself.
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Other Tests

The following other tests may be indicated in patients with Noonan syndrome:

  • Any child suspected of having Noonan syndrome requires a detailed cardiac workup. This includes ECG, echocardiography (ECHO), and consultation with a pediatric cardiologist.
  • Assessment of development is necessary to identify any delays and allow for intervention. Full-scale intelligence quotient (IQ) ranges from 48-130, with a mean of 86.1 (approximately one standard deviation [SD] below the general population mean). Approximately 25% of patients with Noonan syndrome have mental retardation.
  • The incidence of progressive high-frequency sensorineural hearing loss may be as high as 50%. Thus, audiologic evaluation is indicated.
  • DNA-based testing of the 4 known causative genes is available on a commercial basis and can be considered for confirmation of diagnosis. Unless a known mutation is present in a family, negative (ie, normal) test findings do not rule out a diagnosis of Noonan syndrome.
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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

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  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].

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  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].

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  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].

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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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