In 70% of LQTS cases, loss-of-function mutations affect genes encoding for cardiac potassium channels, particularly KV7.1 [type 1 LQTS (LQT1), KCNQ1 gene [2]], KV11.1 or human ether-à-go-go-related gene (hERG) (LQT2, KCNH2 gene [3]), and Kir2.1 (LQT7, KCNJ2 gene [4]). The gene discussed is KCNJ2; the disease is familial long QT syndrome.