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Diseases

Genetic and Rare Diseases Information Center (GARD)

Other Names for this Disease
  • Female Pseudo-Turner Syndrome
  • Male Turner Syndrome
  • Noonan-Ehmke syndrome
  • Pseudo-Ullrich-Turner syndrome
  • Ullrich-Noonan syndrome
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Overview



What is Noonan syndrome?

How is Noonan syndrome inherited?

How might Noonan syndrome be treated?


What is Noonan syndrome?

Noonan syndrome is a genetic disorder that causes abnormal development of multiple parts of the body.[1] Characteristics of the syndrome include a distinctive facial appearance, short stature, a broad or webbed neck, congenital heart defects, bleeding problems, skeletal malformations, and developmental delay.[2][3] Noonan syndrome may be caused by mutations in any one of several genes including the PTPN11, KRASRAF1SOS1NRAS and BRAF genes.[4] It is sometimes referred to as a specific subtype based on the specific, mutated gene that causes the syndrome in an affected individual. It is typically inherited in an autosomal dominant manner, although in many individuals with Noonan syndrome, the mutation occurs for the first time and neither of the parents has the condition.[2][3]
Last updated: 9/28/2012

How is Noonan syndrome inherited?

Noonan syndrome is inherited in an autosomal dominant manner, which means one copy of the altered gene in each cell is sufficient to cause the condition.[2][3][5] Each child of an individual with Noonan syndrome has a 50% (1 in 2) chance to inherit the condition.

In about one-third to two-thirds of families, one of the parents also has Noonan syndrome.[3] In other families, the condition results from a new mutation in the gene and there is no history of the condition in the family.[2]
Last updated: 10/1/2013

How might Noonan syndrome be treated?

Unfortunately, there is no cure for Noonan syndrome. Treatment generally focuses on the specific signs and/or symptoms that an affected individual has. Treatment of the complications associated with Noonan syndrome is generally standard, and does not differ from treatment in the general population for each individual complication.[6] Management may require the coordinated efforts of a team of specialists.[7]

In individuals with congenital heart defects, treatment with certain medications, surgical intervention, and/or other techniques may be necessary. Any surgical procedures depend upon the location, severity, and/or combination of abnormalities and their symptoms. heart problems, arteriovenous abnormalities and/or lymphatic malformations that may be present are taken into consideration during decisions concerning surgical procedures.[7]

For those who also have thrombocytopenia, platelet dysfunction, and/or coagulation factor deficiencies, physicians, dentists, and/or other health care workers may recommend certain preventive measures before or during surgery to control possible abnormal bleeding. In addition, respiratory infections should be treated promptly and aggressively. Because of the potentially increased risk of bacterial infection of the lining of the heart (endocarditis) and the heart valves, affected individuals with certain heart defects, such as atrial septal defects, may be given medication prior to any surgical procedures (including dental procedures).[7]

In affected males with cryptorchidism, surgery should be performed to move undescended testes into the scrotum and attach them in a fixed position. This surgery is typically performed before 5 years of age to help prevent the risk of infertility.[7]

Early intervention may be important in helping children with Noonan syndrome reach their potential. Special services that may be beneficial to affected children may include special remedial education, speech therapy, physical therapy, and other medical, social, and/or vocational services. The short stature in patients with Noonan syndrome can be treated with growth hormone which has been shown to improve final adult height.[7]
Last updated: 10/1/2013

References
  1. Haldeman-Englert C. Noonan syndrome. MedlinePlus. 2009; http://www.nlm.nih.gov/medlineplus/ency/article/001656.htm. Accessed 3/2/2010.
  2. Noonan syndrome. Genetics Home Reference (GHR). 2007; http://ghr.nlm.nih.gov/condition=noonansyndrome. Accessed 3/2/2010.
  3. Learning About Noonan Syndrome. National Human Genome Research Institute (NHGRI). 2009; http://www.genome.gov/25521674. Accessed 3/2/2010.
  4. Noonan syndrome. Genetics Home Reference. March 2011; http://ghr.nlm.nih.gov/condition/noonan-syndrome. Accessed 7/16/2011.
  5. Allanson JE. Noonan Syndrome. GeneReviews. 2008; http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=noonan. Accessed 3/2/2010.
  6. Judith E Allanson. Noonan Syndrome. GeneReviews. October 7, 2008; http://www.ncbi.nlm.nih.gov/books/NBK1124/#noonan.Management. Accessed 7/16/2011.
  7. Noonan Syndrome. NORD. February 18, 2009; http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/412/viewAbstract. Accessed 7/17/2011.