SOS1 and atrial septal defect: Based on these findings and preliminary observations suggesting that a distinct class of mutations in NS disease might be implicated in isolated CHDs [Greenway et al., 2009; Pandit et al., 2007], and given the relatively “mild” developmental and growth related phenotype documented in a significant proportion of SOS1 mutation-positive subjects, we evaluated the possible contribution of germline SOS1 gene lesions in apparently nonsyndromic PS, ASD, and VSD.