PTPN11 and pulmonary valve stenosis: Subsequent studies revealed that PTPN11 variants are found in ~50% of all cases of NS, that individuals carrying PTPN11 mutations are more likely to have pulmonary valve stenosis and less likely to have hypertrophic cardiomyopathy (HCM), and that all de novo PTPN11 variants originate from the paternal copy in the presence of a paternal age effect (Tartaglia et al., 2002; Tartaglia, Cordeddu, et al., 2004).