Noonan syndrome

How is Noonan syndrome inherited?

Noonan syndrome is inherited in an autosomal dominant manner. This means that having one changed or mutated copy of the responsible gene in each cell is enough to cause the condition. Each child of a person with Noonan syndrome has a 50% (1 in 2) chance to inherit the condition.

In other cases, the change in one of the genes that can cause Noonan syndrome is new and not found in either parent. This means that the genetic change was not passed down from either the mother or the father, but instead occurred for the first time (de novo) in the child who has the syndrome. New changes or mutations in a gene can happen by mistake during the making of the egg or the sperm.

Last updated on 05-01-20

What is the long-term outlook for people with Noonan syndrome?

There is a wide range in the nature and severity of signs and symptoms that may be present in people with Noonan syndrome, so the long-term outlook (prognosis) and life expectancy may differ among affected people. Studies generally suggest that long-term outcome depends largely on the presence and severity of congenital heart defects. Death in affected people has been frequently associated with the presence of complex left ventricular disease. Studies have indicated that people with Noonan syndrome have a 3-fold higher mortality rate than those in the general population.

Some affected people have ongoing health problems due to congenital heart defects, lymphatic vessel dysplasia, urinary tract malformations, blood disorders, or other associated health issues. However, with special care and counseling, the majority of children with Noonan syndrome grow up and function normally as adults. Signs and symptoms tend to lessen with age, and new medical problems associated with the condition are generally not expected to appear in adulthood.

Last updated on 05-01-20

Name: RASopathiesNet Email: Url:
Name: Noonan Syndrome Foundation 1840 W. Whittier Blvd. #195
La Habra, CA, 90631,
Toll Free: 866-875-8928 Fax : 866-875-1258 Email: Url:

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The RareGuru disease database is regularly updated using data generously provided by GARD, the United States Genetic and Rare Disease Information Center.

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