Paramyotonia congenita and hypokalemic periodic paralysis in a family with mutation p.R1448H in α-subunit type IV of voltage gated sodium channel gene

Abstract

Objective \nThrough description of the clinical, electrophysiological, pathological and gene sequencing characteristics of a family diagnosed as paramyotonia congenita and hypokalemic periodic paralysis to broaden the understanding of skeletal muscle channel disease and provide the reference for clinical diagnosis. \n \n \nMethods \nThe clinical manifestation, electromyography, muscle pathology and gene sequencing of a family diagnosed as paramyotonia congenita and hypokalemic periodic paralysis in the First Hospital of Shanxi Medical University in October 2017 were collected. \n \n \nResults \nThe proband represented myotonia and episodic muscle weakness, and the manifestations of different patients of the family were varied, including myotonia, episodic muscle weakness or myotonia and episodic muscle weakness. The electromyography of the proband showed myotonic potential, and the compound muscle action potential decreased by 36% in 40 minutes after exercise in the long exercise test in cold environment (11 ℃). The gene sequencing showed α-subunit type Ⅳ of voltage gated sodium channel (SCN4A) gene p.R1448H mutation. \n \n \nConclusions \nThe proband presented with paramyotonia congenita and hypokalemic periodic paralysis. Family clinical manifestations suggested phenotypic heterogeneity. The long exercise text in cold environment (11 ℃) confirmed the diagnosis of the proband as paramyotonia congenita and hypokalemic periodic paralysis. Family gene sequencing showed that the mutation of p.R1448H in SCN4A gene was the pathogenic gene mutation site of paramyotonia congenita and hypokalemic periodic paralysis. \n \n \nKey words: \nHypokalemic periodic paralysis;\xa0Paramyotonia congenita;\xa0SCN4A gene