,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. This evidence concerns the gene LETM1 and Growth delay.