PTPN11 and Noonan syndrome: PTPN11 mutations cause approximately 50% of Noonan syndrome, an autosomal dominant disorder associated with several congenital cardiac defects, including pulmonary stenosis, hypertrophic cardiomyopathy, and atrioventricular septal defects (Sarkozy et al., 2003; Weismann et al., 2005).