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Noonan syndrome is a genetic disorder that causes abnormal development of multiple parts of the body. Features of Noonan syndrome may include a distinctive facial appearance, short stature, a broad or webbed neck, congenital heart defects, bleeding problems, problems with bone structure (skeletal malformations), and developmental delay. Noonan syndrome may be caused by a mutation in any of several genes, and can be classified into subtypes based on the responsible gene. It is typically inherited in an autosomal dominant manner, but many cases are due to a new mutation and are not inherited from either parent. Treatment depends on the symptoms present in each person.
Noonan syndrome belongs to a group of related conditions called the RASopathies. These conditions have some overlapping features and are all caused by genetic changes that disrupt the body's RAS pathway, affecting growth and development. Other conditions in this group include:
Source: GARD Last updated on 05-01-20
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
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
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