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| DiseaseID |
HGD52 |
| Genetic
Disorder |
Noonan Syndrome
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| Gene
Name |
protein tyrosine phosphatase, non-receptor type 11 (Noonan syndrome 1) |
| Description |
Noonan syndrome is a disorder that involves unusual facial characteristics, short stature, heart defects present at birth, bleeding problems, developmental delays, and malformations of the bones of the rib cage. Noonan syndrome is caused by changes in one of several autosomal dominant genes. A person who has Noonan syndrome may have inherited an altered (mutated) gene from one of his or her parents, or the gene change may be a new change due to an error carried by the egg or sperm or occurring at conception. Alterations in three genes - PTPN11, SOS1 and KRAS - have been identified to date. Noonan syndrome is present in about 1 in 1,000 to 1 in 2,500 people.
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| Symptoms |
A characteristic facial appearance.
Short stature.
Heart defect present at birth (congenital heart defect).
A broad or webbed neck.
Minor eye problems such as strabismus in up to 95 percent of individuals.
Bleeding problems such as a history of abnormal bleeding or bruising.
An unusual chest shape with widely-spaced and low set nipples.
Developmental delay of varying degrees, but usually mild.
In males, undescended testes (cryptorchidism).
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| Causes |
Defects in the KRAS and PTPN11 genes 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 severe or atypical form of Noonan syndrome. Problems with these genes cause certain proteins involved in growth and development to become overactive.
Noonan syndrome is inherited, which means it is passed down through families. It is an autosomal dominant condition. However, the fact that some children do not have a parent with Noonan syndrome likely reflects that some cases may occur due to new mutation in a gene. |
| Diagnosis |
The diagnosis of Noonan syndrome is based on the person's clinical symptoms and signs. The specialist examines the person looking for the specific features of Noonan syndrome. Individuals who have Noonan syndrome have normal chromosome studies. Three genes - PTPN11, SOS1 and KRAS - are the only genes that are known to be associated with Noonan syndrome. About 50 percent of individuals who have Noonan syndrome are found to have gene alterations (mutations) in the PTPN11 gene. About 10 percent of individuals who have Noonan syndrome have mutations in the SOS1 gene while less than 5 percent of affected individuals have mutations in the KRAS gene. Genetic testing of all three genes is available clinically
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| Treatment |
Treatment for individuals who have Noonan syndrome is based on their particular symptoms. Heart problems are treated in the same way as they are for individuals in the general population. Early intervention programs are used to help with developmental disabilities, when present. Bleeding problems that can be present in Noonan syndrome may have a variety of causes and are treated according to their cause. Growth problems may be caused by lack of growth hormone and may be treated with growth hormone treatment. Symptoms such as heart problems are followed on a regular basis. |
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