New phenotype and neonatal onset of sodium channel myotonia in a child with a novel mutation of SCN4A gene

Brain & Development
Carlo FuscoLorenzo Maggi

Abstract

Myotonia is rare in newborns, and not well-known. Mutations of the skeletal muscle sodium channel gene SCN4A are associated with several neuromuscular disorders including sodium channel myotonias. We reported a 4-year-old female who presented with diffuse stiffness, bilateral clubfoot, hip dislocation, facial dysmorphisms and myotonia at birth. At 4 years of age the neurological examination showed characteristic "Hercules-like appearance" hyporeflexia, mild grip myotonia and bilateral pes cavus. The stiffness was worst at rest and in the early morning which improves with exercise. The clinical features, electromyography findings and diagnostic work-up of this patient and of child's mother were described. The clinical follow-up led us to the diagnosis of sodium channel myotonia with atypical neonatal onset. Mutation analysis in the patient and in child's mother revealed a novel heterozygous p.N1180I mutation in exon 19 of SCN4A gene. We recommend that in newborns with stiffness, peripheral contractures and myotonia, the sequence analysis of SCN4A gene should be performed.

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Citations

Jan 12, 2016·The Journal of Clinical Investigation·Yavuz BayramJames R Lupski
Feb 17, 2018·Chinese Medical Journal·Yang-Qi XuLi Cao
Dec 17, 2020·Journal of Neuromuscular Diseases·Jean-François DesaphyBertrand Fontaine
Apr 7, 2021·Journal of Medical Genetics·Annie LaquerriereJudith Melki
Aug 12, 2021·Neurological Sciences : Official Journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology·Andrea RigamontiAndrea Salmaggi

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