MYL4 and familial disease: Recently, other mutations have been described, in the genes coding for Myosin Light Chain 4 (MYL4), which encodes the atrial-specific myosin essential light chain [35,48,49]; these mutations could be related to AS, but also to other familial diseases (such as AF, LVNC, and other neuromuscular disorders), as described by Gollob [48].