NSD2 and Growth delay: ,60 It has been previously speculated that the most probable cause of growth deficiency, microcephaly, and the characteristic facial features in WHS is due to haploinsufficiency of WHSC1, a region located far from LETM1.61 The expression of mild non-neurological symptoms of WHS in our cohort could be due to either putative interaction between LETM1 and WHSC1 or other undiscovered mechanisms, including those intrinsically caused by LETM1 deficiencies.