Cardiac pathology in 6 cases of fetal hydrops due to Noonan syndrome

Objective Noonan syndrome (NS) is a common, autosomal dominant, frequently de novo condition due to mutations in RAS-MAPK pathway genes. Presentation is variable, usually in infancy or early childhood, and includes poor postnatal growth, cardiac abnormalities, dysmorphic features and lymphatic dysplasia. The classic cardiac abnormalities are pulmonary valve dysplasia and hypertrophic cardiomyopathy, but other cardiac anomalies are reported. Prenatal US scan showing nuchal translucency or cystic hygroma may suggest NS, and fetal hydrops is a recognised presentation.