Loss-of-function mutations in the KCNQ1 and KCNH2 genes (LQT1 and LQT2, respectively) account for ~65% of all LQTS cases, and gain-of-function mutations in the SCN5A gene (LQT3) account for 10% of all LQTS cases [3,4]. The gene discussed is KCNQ1; the disease is familial long QT syndrome.