KCNH2 and familial long QT syndrome: Of particular note in cardiac arrhythmia genes, four pathogenic and two candidate pathogenic variants were found in the three key LQTS genes, including a de novo SCN5A Ile397Val variant, a Gly924Ala and Arg744* nonsense variant in KCNH2, and a Tyr662* nonsense variant in KCNQ1 (Figure 2).