The cause of Noonan syndrome is a mutation in a particular gene. Currently, scientists know of eight genes that can cause Noonan syndrome.

The mutation can be inherited from a parent who carries the defective gene (autosomal dominant), or it can develop because of a new mutation in children who don't have a genetic predisposition for the disease. Children who have one parent with Noonan syndrome have a 50 percent chance of developing the disorder.

Defects in these genes cause them to produce proteins that are continually active. Because these genes play a role in the formation of many tissues throughout the body, this constant activation of their proteins disrupts the normal process of cell growth and division.

Aug. 03, 2013