KCNJ5 or the potassium inwardly-rectifying channel, subfamily J, member 5 is the gene involved in in congenital long QT syndrome 13 (LQTS13), the latest of the long QT syndromes, described in 2010 by Yang and associates [Yang, Y et al. Identification of a Kir3.4 mutation in congenital long QT syndrome. Am. J. Hum. Genet. 2010;86: 872-880]. The protein encoded by this gene is controlled by the G proteins and allows entry of potassium into the cell. It is an integral membrane protein (inward rectifier type of potassium channel). Their voltage dependence is regulated by extracellular potassium concentration, with the voltage range of channel opening shifting towards more positive voltages with an increase in extra cellular potassium. Blockage of the outward current by internal magnesium is the main reason of inward rectification. Congenital long QT syndrome 13 (LQTS 13) caused by a defect in KCNJ5 is characterized by prolonged QT interval and polymorphic ventricular tachycardia with syncope and sudden death in response to exercise or emotional stress. One of the affected family members had a sudden death in early infancy. KCNJ5 gene is located on chromosome 11 (11q24; long arm of chromosome 11 at position 24). CIR, GIRK4, KATP1 and KIR3.4 are other names for KCNJ5 gene /products.