Paralysis Periodica Paramyotonica Caused by SCN4A Arg1448Cys Mutation

Abstract

Paralysis periodica paramyotonica is an overlapping disease that shares the features of paramyotonia characteristic of paramyotonia congenita (PC) and periodic paralysis characteristic of hyperkalemic periodic paralysis. We report the case of a 23-year-old man with paralysis periodica paramyotonica. His father and a younger brother also exhibited a similar phenotype. A SCN4A Arg1448Cys mutation was detected in this family. The affected family members exhibited marked shifts in compound muscle action potential amplitudes on exercise test, and muscle weakness could be induced by potassium loading and cold exposure. This case demonstrates that SCN4A Arg1448Cys can produce paralysis periodica paramyotonica. Other genetic or environmental factors may modulate the manifestation of SCN4A Arg1448Cys mutation.

Mutations of SCN4A gene cause different diseases: 2 case reports and literature review

“…Similar or even same mutations in the same gene (SCN4A) can cause distinct clinical disorders. 5 In this study, we reported one sporadic individual of periodic paralysis and one autosomal-dominant paramyotonia family, both of whom were caused by mutations of SCN4A gene but having completely different phenotypes. In addition, we carried out literature review by summarizing reported clinical features of the SCN4A mutations and established the genotype-phenotype correlations to provide guidance for diagnosis.…”

Tubular aggregates in paralysis periodica paramyotonica with T704M mutation of SCN4A

“…6 They seem to be the myopathological hallmarks in familial TA myopathies [OMIM%160565], most of which have an unclear genetic basis. [7][8][9][10] Sodium channel, voltage-gated, type IV, alpha subunit (SCN4A) gene mutation can cause several allelic disorders [11][12][13][14] including hyper-, hypo-and normokalemic periodic paralysis, paramyotonia congenita, potassiumaggravated myotonia and permanent mytonia. 15 In rare situation, the main clinical symptoms of different diseases can overlap, such as paralysis periodica paramyotonica with clinical features of both paramyotonia congenita and hyperkalemic periodic paralysis.…”

Paramyotonia congenita: From clinical diagnosis to in silico protein modeling analysis

“…PMC is characterized by myotonia accompanied with post‐myotonia muscle weakness, while SCM is characterized by myotonia without muscle weakness. Based on the recent non‐dystrophic myotonia classification by Matthews et al ., “Paramyotonia congenita of von Eulenburg” 2 or “paralysis periodica paramyotonia” 3 in the previous papers may fall into PMC, while “paramyotonia congenita without paralysis” 4 or “pure paramyotonia congenita” 5 may fall into SCM.…”