This includes pulmonary valvular stenosis (50–60%), atrial septal defects (10–25%), ventricular septal defects (5–20%) and hypertrophic cardiomyopathy (12–35%). Lungs
Restrictive lung function has been reported in some people. Gastrointestinal
A number of diverse gastrointestinal (GI) symptoms have been associated with Noonan syndrome. These include swallowing difficulties, low gut motility, gastroparesis (delayed gastric emptying), intestinal malrotation, and frequent or forceful vomiting. These digestive issues may lead to decreased appetite, failure to thrive from infancy to puberty (75%), and occasionally the need for a feeding tube. Genitourinary system
In some males with Noonan syndrome, testicles do not descend (cryptorchidism). Circulation
Lymphatic anomalies including Posterior cervical hygroma (webbed neck) and Lymphedema may present in people with Noonan syndrome. A number of bleeding disorders have been associated with Noonan syndrome, these include platelet dysfunction, Blood clotting disorders, partial deficiency of factor VIII:C, partial deficiency of factor XI:C, partial deficiency of factor XII:C, and an imbalance of plasminogen activator inhibitor type-1 (PAI-1) and tissue plasminogen activator (t-PA) activity. It has been associated with Von Willebrand disease, Amegakaryocytic thrombocytopenia (low platelet count), prolonged activated partial thromboplastin time, combined coagulation defects. When present, these Noonan-syndrome accompanying disorders can be associated with a predisposition to bruise easily, or hemorrhage. Neurological
Occasionally, Chiari malformation (type 1), may occur, which can lead to hydrocephalus. Seizures have also been reported. Causes
Recurrence in siblings and apparent transmission from parent to child has long suggested a genetic defect with autosomal dominant inheritance and variable expression.
Prognosis is therefore largely dependent on the presence or absence of cardiac disease, as well as the type and severity of the disease (if disease is present). Most notably, Noonan syndrome with hypertrophic cardiomyopathy is associated with increased mortality. History
Jacqueline Noonan was practicing as a pediatric cardiologist at the University of Iowa when she noticed that children with a rare type of heart defect, valvular pulmonary stenosis, often had a characteristic physical appearance, with short stature, webbed neck, wide spaced eyes, and low-set ears. Both boys and girls were affected. These characteristics were sometimes seen running in families but were not associated with gross chromosomal abnormalities. She studied 833 people with Noonan syndrome at the congenital heart disease clinic, looking for other congenital abnormalities, and, in 1963, presented a paper: "Associated non-cardiac malformations in children with congenital heart disease". This described 9 children who in addition to congenital heart disease had characteristic facial features, chest deformities and short stature. Dr. John Opitz, a former student of Dr. Noonans, first began to call the condition "Noonan syndrome" when he saw children who looked like those whom Dr. Noonan had described. Dr. Noonan produced a paper titled "Hypertelorism with Turner Phenotype" in 1968 where she studied 19 patients who displayed symptoms indicative of Noonans Syndrome. In 1971, at the Symposium of Cardiovascular defects, the name Noonan syndrome became officially recognized. References


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