KCNH2 and familial long QT syndrome: To date, pathogenic variants associated with LQTS have been identified in 19 genes: 15 following an autosomal-dominant pattern of inheritance (AKAP9, ANK2, CACNA1C, CALM1, CALM2, CALM3, CAV3, KNCE2, KCNH2, KCNJ2, KCNJ5, RYR2, SCN1B, SCN4B, SCN5A and SNTA1), one following an autosomal-recessive pattern (TRDN), and two following both autosomal-dominant and -recessive patterns (KCNQ1 and KCNE1) (Figure 2).