Notably, a similarly sized (544 kb) rare copy-number gain overlapping the NXN gene was reported by another group to be associated with ToF.10 As PAVSD may be considered to be at the more severe end of the spectrum of the cardiac phenotype in relation to ToF, the loss of one copy at this locus may implicate a more profound cardiac developmental effect for CHD than would a gain of copy. This evidence concerns the gene NXN and atrial septal defect, ostium primum type.