NSD2 and Wolf-Hirschhorn syndrome: Variable-sized deletions in chromosome 4p16.3, including NSD2, cause Wolf–Hirschhorn syndrome (also known as 4p-syndrome; WHS; OMIM 194190), which is characterized by growth retardation, developmental delay/intellectual disability (DD/ID), microcephaly, hypotonia, and congenital malformations (Bergemann et al., 2005).