Paramyotonia congenita in a family with SCN4A gene mutation
10.3760/cma.j.cn113694-20250126-00061
- VernacularTitle:SCN4A基因突变导致的先天性副肌强直一家系
- Author:
Mengjie XIA
1
;
Qiongfang ZHANG
;
Qian SUN
;
Zhenyu REN
;
Haiyan ZHOU
Author Information
1. 上海交通大学医学院附属瑞金医院神经内科，上海 200025
- Publication Type:Journal Article
- Keywords:
Paramyotonia congenita;
Periodic paralysis;
SCN4A gene
- From:
Chinese Journal of Neurology
2025;58(4):387-395
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To report the clinical, electrophysiological, and genetic mutation characteristics of a family with paramyotonia congenita, to enhance clinical understanding of ion channelopathies, provide better guidance for clinical diagnosis, and optimize treatment plans.Methods:The clinical data, nerve conduction studies, needle electromyography, long exercise test, short exercise test, and whole-exome sequencing results of the proband with paramyotonia congenita and his family members admitted to Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, in August 2023 were collected and analyzed.Results:The proband was a 15-year-old male who presented with episodic muscle weakness for 1 year, accompanied by elevated creatine kinase during episodes. Between the ages of 3 and 4, he exhibited facial and bilateral hand myotonia triggered by cold exposure. His mother, sister, maternal grandmother, maternal aunt and uncle also displayed similar cold-induced facial and hand myotonia during childhood. Additionally, his cousin exhibited walking difficulties, frequent falls, mild difficulty in opening eyes after closure, and mild chewing and swallowing difficulties at the age of 1. Electromyography of the proband showed widespread myotonic discharges and myopathic impairment, while the electromyography of his mother and sister revealed only widespread myotonic discharges. The proband′s long exercise test results were consistent with periodic paralysis, while the short exercise test results aligned with paramyotonia congenita. His sister′s long exercise test results were within normal range, while the short exercise test results of his mother and sister were consistent with paramyotonia congenita. Genetic testing of the family revealed that all tested patients carried a heterozygous SCN4A mutation, c.4343G>A (R1448H). Conclusions:The R1448H mutation in the SCN4A gene is the genetic cause of this family. Patients carrying the SCN4A R1448H mutation may exhibit clinical features of cold-induced myotonia with or without episodic muscle weakness. In addition to widespread myotonic discharges on electromyography, certain patients may also show myopathic impairment. The long and short exercise tests can further assist in differentiating various types of myotonia and periodic paralysis for clinical diagnosis.
