Noonan syndrome

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Pectus excavatum

Noonan syndrome is a genetic disorder that causes abnormal development of multiple parts of the body. It used to be called Turner-like syndrome because certain symptoms (webbing of neck and abnormally shaped chest) resembled those seen in Turner syndrome.

Defects in four genes (KRAS, PTPN11, RAF1, SOS1) can cause Noonan syndrome. About half of those affected by Noonan syndrome have a PTPN11 mutation. Persons with a defect in the KRAS gene have a more severe form of Noonan syndrome. Those with defects in the RAF1 gene tend to have a particular heart problem (hypertrophic cardiomyopathy). Problems with these genes cause certain proteins involved in growth and development to become overactive.

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Noonan syndrome is inherited, which means it is passed down through families. It is an autosomal dominant condition. This means that only one parent has to provide the faulty gene for the baby to have the syndrome. However, the fact that some children do not have a parent with Noonan syndrome likely means that some cases are not inherited.

Review Date: 08/26/2009
Reviewed By: Chad Haldeman-Englert, MD, Wake Forest University School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org).