SOS1 and atrial septal defect: Similar to what observed in NS subjects with PTPN11 mutations [Tartaglia et al., 2002; Zenker et al., 2004], SOS1 mutation-positive patients exhibit a high prevalence of PS (68% of cases), which was typically associated with ASD (35% of cases), a relatively high occurrence of atrial and ventricular septal defects (39% of cases), and a low prevalence of HCM (<10% of cases).