NSD2 and Wolf-Hirschhorn syndrome: Although haploinsufficiency of both WHSC1 and WHSC2 are thought to underlie many of the core clinical features of WHS, other genes additionally contribute to features such as facial dysmorphology, microcephaly and growth retardation, reinforcing the multigenic nature of this disorder (Engbers et al., 2009; Hammond et al., 2012; Hannes et al., 2012; South et al., 2007; South et al., 2008; Van Buggenhout et al., 2004).