iGeneTech Bioscience Co., Ltd.
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Myotonia congenita and periodic hypokalemia paralysis in a consanguineous marriage pedigree: Coexistence of a novel CLCN1 mutation and an SCN4A mutation

Chenyu Zhao; DongFang Tang; Hui Huang; Haiyan Tang; Yuan Yang; Min Yang; Yingying Luo; Huai Tao; Jianguang Tang; Xi Zhou; Xiaoliu Shi
PLoS ONE 2020;15(5):e0233017 DOI:10.1371/journal.pone.0233017
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Myotonia congenita and hypokalemic periodic paralysis type 2 are both rare genetic channelopathies caused by mutations in the CLCN1 gene encoding voltage-gated chloride channel CLC-1 and the SCN4A gene encoding voltage-gated sodium channel Nav1.4. The patients with concomitant mutations in both genes manifested different unique symptoms from mutations in these genes separately. Here, we describe a patient with myotonia and periodic paralysis in a consanguineous marriage pedigree. By using whole-exome sequencing, a novel F306S variant in the CLCN1 gene and a known R222W mutation in the SCN4A gene were identified in the pedigree. Patch clamp analysis revealed that the F306S mutant reduced the opening probability of CLC-1 and chloride conductance. Our study expanded the CLCN1 mutation database. We emphasized the value of whole-exome sequencing for differential diagnosis in atypical myotonic patients.