Genetic spectrum and founder effect of non-dystrophic myotonia: a Japanese case series study

Yuan, Jun‐Hui; Higuchi, Yujiro; Hashiguchi, Akihiro; Ando, Masahiro; Yoshimura, Akinobu; Nakamura, Tomonori; Sakiyama, Yusuke; Takashima, Hiroshi

doi:10.1007/s00415-022-11305-6

Cited by 3 publications

(6 citation statements)

References 46 publications

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“…Rarely, there is incomplete penetrance among family members, with some family members remaining asymptomatic despite harboring the mutation. 45 The Na1.4 alpha subunit consists of four homologous but not identical domains (DI-DIV), each with six transmembrane segments (S1-S6). Depolarization of the channel is responsible for forming and conducting the muscle fiber action potential that leads to muscle contraction.…”

Section: Myotonia Congenitamentioning

confidence: 99%

“…By contrast, loss of function of the regular fast/ slow inactivation process leads to paralysis and is discussed in a later section. 45 The clinical characteristics of PMC, first described by von Eulenburg, 46 include several features that help to distinguish it from other nondystrophic myotonias. Transient muscle stiffness, often exacerbated by cold temperatures and worsened with exercise, are the hallmark features of PMC.…”

Section: Myotonia Congenitamentioning

confidence: 99%

“…27 Men and women tend to be affected equally in PMC. 45 They can rarely exhibit intermittent paralysis and worsening of symptoms with a high potassium load. 49 Clinical symptoms of PMC often remain unchanged throughout life, with muscle atrophy, hypertrophy, or persistent weakness being atypical of this disease.…”

Section: Myotonia Congenitamentioning

confidence: 99%

“…SCN4A mutations are more common in East Asia, whereas CLCN1 mutations are more common in European populations. Rarely, there is incomplete penetrance among family members, with some family members remaining asymptomatic despite harboring the mutation 45 …”

Section: Channelopathies With Myotoniamentioning

confidence: 99%

“…The persistently increased sodium current causes sustained sarcolemmal depolarization and increased excitability of the muscle fiber membrane. By contrast, loss of function of the regular fast/slow inactivation process leads to paralysis and is discussed in a later section 45 …”

Section: Channelopathies With Myotoniamentioning

confidence: 99%

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Muscle channelopathies: A review

McGowan,

Schwaede,

De Simone

et al. 2023

Annals of the Child Neurology Society

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BackgroundMuscle channelopathies are a rare and heterogeneous group of disorders that can be clinically challenging and functionally disabling. These disorders can present in both adult and pediatric age groups. These disorders have been known since the turn of the 20th century, with a steady evolution in terms of understanding the pathophysiology, phenotype, diagnostic, and treatment modalities over the last three decades.MethodsWe present a comprehensive review of muscle channelopathies that includes nondystrophic myotonias and periodic paralyses. The disorders in this review have been classified based on the presence or absence of myotonia on either the clinical exam or on electrophysiological testing. The historical background, genetics, pathophysiology, phenotypic presentations, and treatment modalities of each disorder reveal similarities as well as specific nuances in the disease phenotypes. Neurophysiologic testing shows differences in responses on routine and exercise testing and can narrow the differential within subsets of nondystrophic myotonias and periodic paralyses. The advances in genetics further aid in specifying which of the putative channels are at fault. Management can then be guided by knowledge of the causative gene and involves either avoidance of triggers or channel‐based therapeutics.ConclusionMuscle channelopathies are rare, but a high index of suspicion along with a knowledge of the phenotype will help guide neurophysiological and genetic testing. A muscle channelopathy diagnosis, subsequently, can assist in avoiding triggers and directing treatments.

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Section: Myotonia Congenitamentioning

confidence: 99%

Section: Myotonia Congenitamentioning

confidence: 99%

Section: Myotonia Congenitamentioning

confidence: 99%

Section: Channelopathies With Myotoniamentioning

confidence: 99%

Section: Channelopathies With Myotoniamentioning

confidence: 99%

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Muscle channelopathies: A review

McGowan,

Schwaede,

De Simone

et al. 2023

Annals of the Child Neurology Society

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Clinical and genetic characteristics of myotonia congenita in Chinese population

He,

Qiu,

Xiong

et al. 2024

Channels

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A pedigree of myotonia congenita with a novel mutation p.F343C of the <i>CLCN1</i> gene

Nakamura,

Sato,

Kakiuchi

et al. 2024

Rinsho Shinkeigaku

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A Japanese woman experienced slowness of movement in her early teens and difficulty in opening her hands during pregnancy. On admission to our hospital at 42 years of age, she showed grip myotonia with warm-up phenomenon. However, she had neither muscle weakness, muscle atrophy, cold-induced symptomatic worsening nor episodes of transient weakness of the extremities. Needle electromyography of the first dorsal interosseous and anterior tibial muscles demonstrated myotonic discharges. Whole exome sequencing of the patient revealed a heterozygous single-base substitution in the CLCN1 gene (c.1028T>G, p.F343C). The same substitution was identified in affected members of her family (mother and brother) by Sanger sequencing, but not in healthy family members (father and a different brother). We diagnosed myotonia congenita (Thomsen disease) with a novel CLCN1 mutation in this pedigree. This mutation causes a single amino acid substitution in the I-J extracellular loop region of CLCN1. Amino acid changes in the I-J loop region are rare in an autosomal-dominantly inherited form of myotonia congenita. We think that this pedigree is precious to understand the pathogenesis of myotonia congenita.

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Genetic spectrum and founder effect of non-dystrophic myotonia: a Japanese case series study

Cited by 3 publications

References 46 publications

Muscle channelopathies: A review

Muscle channelopathies: A review

Clinical and genetic characteristics of myotonia congenita in Chinese population

A pedigree of myotonia congenita with a novel mutation p.F343C of the <i>CLCN1</i> gene

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