Noonan syndrome is a disorder that involves unusual facial characteristics, short stature, heart defects present at birth, bleeding problems, developmental delays, and malformations of the bones of the rib cage. A PTPN11 gene mutation was identified in 104 (38.25%) of 274 patients with Noonan syndrome. Heart defect was present in 85%. The most prevalent congenital heart defects were pulmonary valve stenosis (60%), atrial septal defect, ostium secundum type (25%), and stenosis of the peripheral pulmonary arteries (in at least 15%). Treatment for individuals who have Noonan syndrome is based on their particular symptoms. Heart problems are treated in the same way as they are for individuals in the general population.
Early intervention programs are used to help with developmental disabilities, when present. Bleeding problems that can be present in Noonan syndrome may have a variety of causes and are treated according to their cause. 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.