Noonan Syndrome

Noonan syndrome is a multisystemic autosomal dominant genetic disorder with broad expressivity and significant intra-familial variability. It is characterized by distinctive facial features, developmental delay, learning difficulties, short stature, congenital heart disease, renal anomalies, lymphatic malformations, and bleeding difficulties. Significant morbidity and mortality are most commonly associated with congenital hypertrophic cardiomyopathy, but less often due to recurrent chylous effusion or malignancy. Because of known genotype–phenotype correlations, genetic testing can be helpful in tailoring anticipatory guidance. Genotype is also necessary when considering the use of pathway inhibitors. Neurodevelopmental complications are common, most often mild to moderate, and children benefit from detailed neuropsychological testing to tailor intervention services to their cognitive profile. Individuals with NS require lifelong monitoring for the potential complications of each age group.