Noonan syndrome is an autosomal dominantly inherited disease characterized by short stature, congenital heart defect and delayed mental development of varying degree. Patients with Noonan syndrome also have a characteristic appearance: short neck, cervical skin fold, low set ears, hypertelorism. Additionally lymphatic system dysplasia may occur, which is the basis of cystic hygroma and occipital fold enlargement in the fetus.
The incidence of Noonan syndrome is about 1:1000-2500. Noonan syndrome is genetically heterogeneous. In 50% of patients mutations occur in the PTPN11 gene. 10% of cases are associated with mutations in the SOS1 gene, 3% in the RAF1 gene and 1% in the KRAS gene.
Indications for genetic testing:
- Confirmation of clinical diagnosis
- Parental testing in case of a causative mutation has been identified in an affected individual
- Genetic counseling
- Prenatal diagnosis
For further information:
Genetic assessment following increased nuchal translucency and normal karyotype
Pergament E, Alamillo C, Sak K, Fiddler M.
Prenat Diagn. 2011 Mar;31(3):307-10. doi: 10.1002/pd.2718. Epub 2011 Feb 15.