What is Noonan syndrome?
Noonan syndrome is characterized by facial features, short stature, congenital heart defect, and developmental delay. Other findings can include broad or webbed neck, unusual chest shape with superior pectus carinatum and inferior pectus excavatum, cryptorchidism (undescended testes), bleeding problems, and eye differences.
Birth length is usually normal, but final adult height approaches the lower limit of normal. Congenital heart disease occurs in 50%-80% of individuals. Pulmonary valve stenosis, often with dysplasia, is the most common heart defect and is found in 20%-50% of individuals. Hypertrophic cardiomyopathy, found in 20%-30% of individuals, may be present at birth or develop in infancy or childhood. Other structural defects include atrial and ventricular septal defects, branch pulmonary artery stenosis, and tetralogy of Fallot. Up to 25% of individuals with Noonan syndrome have mild intellectual disability. Language impairments are more common in Noonan syndrome than in the general population.