Noonan syndrome is a condition that is characterized by mildly unusual facial characteristics, short stature, heart defects, bleeding problems, skeletal malformations, and many other signs and symptoms. Noonan syndrome is inherited in an autosomal dominant manner. Although many individuals with NS have a de novo mutation, an affected parent is recognized in 30%-75% of families. There is currently no single treatment for Noonan syndrome, but it's often possible to successfully manage many aspects of the disorder. Severe heart defects may need to be repaired with surgery, and growth hormone medication may be used to help prevent restricted growth.
Recurrence risk for parents who do not appear to be affected or who have only some facial features of Noonan syndrome is 5%. Gonadal mosaicism may account for this increase over population risk. Affected individuals have a 50% chance of passing on the disorder with each pregnancy. Alterations in four genes - PTPN11, SOS1, RAF1 and KRAS - have been identified to date.