The proband (IV-2) and the proband's mother (III-3), aunt (III-1) and cousin (IV-1) carried a heterozygous mutation in the KCNJ2 gene at c.199C > T (p. R67W) with hypokalemia and ventricular arrhythmia symptoms (Fig. 1B), which was verified by Sanger sequencing (Fig. 1C). Here, KCNJ2 is linked to Hypokalemia.