KCNJ2 and Cardiodysrhythmic potassium-sensitive periodic paralysis: Andersen-Tawil syndrome (“LQT7”) is a multisystem disorder due to loss-of-function mutations in KCNJ2, the gene encoding the Kir2.1 protein, which assembles in tetramers to build the channels that carry the inward rectifier K+ current (IK1) (38).