MYLK and megacystis-microcolon-intestinal hypoperistalsis syndrome 1: Different autosomal recessive forms of MMIHS are caused by biallelic loss-of-function variants in genes coding for proteins involved in actin–myosin interactions, such as MYH11 (myosin heavy chain; [26], MYLK (myosin-light chain kinase; [28], LMOD1 (leiomodin 1, an actin-binding protein expressed primarily in vascular and visceral smooth muscle [28]; and MYL9 (regulatory myosin-light chain) [45]).