KCNH2 and familial long QT syndrome: The majority of LQTS cases arise from mutations in KCNQ1 (potassium channel voltage-gated KQT-like subfamily member 1; OMIM: 607542), KCNH2 (potassium channel voltage-gated subfamily H member 2; OMIM: 152427), or SCN5A (sodium voltage-gated channel alpha subunit 5; OMIM: 600163) [187].