To study the etiology and pathogenesis of sporadic hypokalemic periodic paralysis (SPP) by sequencing the KCNJ12 and KCNJ18 genes and analyze KCNJ12 mRNA expression by real-time quantitative fluorescent PCR.

Forty-two patients with SPP treated at Dongguan Houjie Hospital from May 2016 to April 2018 were included, and 20 healthy volunteers were used as a control group. The coding regions of KCNJ18 and KCNJ12 genes were sequenced by Sanger method in all subjects, and real-time fluorescence quantitative PCR analysis of KCNJ12 mRNA was performed. The Ct values of the initial copy number of KCNJ12 mRNA between the SPP group and the control group were compared by the independent-samples t-test.

There was no difference in the DNA coding regions of KCNJ12 and KCNJ18 genes between SPP patients and healthy people. Real-time fluorescence quantitative PCR analysis of the KCNJ12 gene showed that the Ct value of the initial copy number of KCNJ12 gene mRNA in SPP patients was significantly lower than that of the healthy control group [(0.62±0.24) vs (1.11±0.15), t=2.65, P=0.02], which indicated that the expression level of KCNJ12 mRNA in SPP patients was significantly lower than that in the control group.

There is no abnormal gene mutation in the coding regions of KCNJ18 and KCNJ12 genes in SPP patients, but the expression of KCNJ12 mRNA is significantly lower than that of healthy population, suggesting that SPP may be caused by abnormal expression of inward-rectifier potassium ion channel gene.