Noonan Syndrome Follow-up

Updated: Apr 22, 2022
  • Author: Margaret M McGovern, MD, PhD; Chief Editor: Luis O Rohena, MD, PhD, FAAP, FACMG  more...
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If a causative mutation is found in patients, parental studies should be offered in order to distinguish familial cases from sporadic ones. If an individual carries a germline mutation, prenatal diagnosis can be offered in future pregnancies. [34] The presentation of Noonan syndrome can vary widely within families.

Prenatal testing for Noonan syndrome can be considered in the absence of a family history when cystic hygroma is seen on ultrasonography and karyotyping of amniocytes is normal.

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.


Patient Education

Once the pattern of inheritance has been identified, parents need to be counseled regarding recurrence risk with each pregnancy. Sporadic cases present minimal recurrence risk to the siblings of the affected child; the exception is parental gonadal mosaicism. Offspring of an affected individual have a 50% chance of developing Noonan syndrome.

Patients with bleeding disorders must be advised against the use of aspirin and aspirin-containing products or other medications that may interfere with coagulation or platelet function.