先天性肌强直1例报告

正先天性肌强直(myotonia congenital,MC)是与CLCN1基因相关的遗传性氯离子通道疾病,以肌肉收缩后舒张困难为主要表现,分为常染色体显性遗传的Thomsen型及常染色体隐性遗传的Becker型。目前,国外对MC相关CLCN1基因突变报道较多,而国内CLCN1基因确诊的MC     

先天性肌强直一家系的临床特点及CLCN1基因突变筛查

目的 探讨先天性肌强直一家系的临床特点及CLCN1基因突变情况。方法 对一先天性肌强直家系中的22例患者的临床资料进行分析。结果 该家系5代68名成员,连续4代共24例发病,男女均有累及;多于婴幼儿期起病,肌强直见于所有患者,16例伴有肌肥大。全部患者肌酶学检查及血电解质正常;2例肌电图检查见自发性肌强直电位;先证者肌活检见肌纤维排列疏松,大小不一,横纹不清,部分肌纤维增生与肥大,肌细胞轻度变性,周围有少量炎性细胞浸润;3例基因检测未发现CLCN1基因的23对外显子突变。结论 该家系为常染色体显性遗传的Thomsen病,患者均有典型的临床表现。CLCN1基因23对外显子筛查未发现突变,表明可能存在遗传异质性。     

先天性肌强直一家系以及散发患者一例的临床、电生理、基因学研究

目的探讨先天性肌强直一家系和散发患者一例的临床、电生理、基因学特点。方法对先天性肌强直的一家系和一例散发的患者进行详细的临床资料搜集,对家系先证者以及相关的亲属进行CLCN1和SCN4A基因测序。结果家系中3代共有7例患者,其中5例患者以及一例无症状的家系成员接受了基因检测,结果发现5例患者携带CLCN1A298 T突变。在散发的患者中发现了S723 R错义杂合突变。结论 CLCN1基因A298 T突变是家系中先天性肌强直患者的致病突变,而S723R是否为散发患者的致病突变需要进一步明确。     

先天性肌强直一家系以及散发患者一例的临床、电生理、基因学研究

目的 探讨先天性肌强直一家系和散发患者一例的临床、电生理、基因学特点。方法 对先天性肌强直的一家系和一例散发的患者进行详细的临床资料搜集,对家系先证者以及相关的亲属进行CLCN1和SCN4A基因测序。结果 家系中3代共有7例患者,其中5例患者以及一例无症状的家系成员接受了基因检测,结果发现5例患者携带CLCN1 A298T突变。在散发的患者中发现了S723R错义杂合突变。结论 CLCN1基因A298T突变是家系中先天性肌强直患者的致病突变,而S723R是否为散发患者的致病突变需要进一步明确。     

广西地区一家系先天性肌强直的临床资料和基因测定

目的探讨先天性肌强直(MC)一家系的临床特点及CLCN1基因部分外显子位点突变的情况。方法收集广西壮族自治区1例MC患者的临床及家系资料,提取家系成员和对照组(无血缘关系的健康体检者6名)的外周静脉血DNA,采用聚合酶链反应(PCR)扩增部分CLCN1基因,测定该基因第3、5、8、13、14、15、16号外显子序列,并对突变位点进行分析。结果 MC患者的6名家系和对照组成员的PCR扩增凝胶电泳分析表明,同一引物对应各样本条带均无显著差异;CLCN1基因被测序的第3、5、8、13、14、15、16号外显子序列均未发现有突变位点。结论该MC患者及家系中患者的MC致病基因位点未位于CLCN1基因这7个外显子序列上,需要对CLCN1基因全外显子序列进行检测分析。     

3例先天性肌强直的临床特点和基因分析

目的 探讨3例先天性肌强直(myotonia congenita,MC)患者的临床特点和基因突变情况.方法 回顾性分析河南省人民医院神经内科2016年1月至2018年11月收治的无亲缘关系的3例MC患者的临床和病理资料,并进行基因检测.结果 3例患者均幼年或少年早期起病,其中例1和例2的首发症状均为下肢肌强直、之后波及...     

先天性肌强直16例临床分析

目的　探讨先天性肌强直的临床特征、诊断及治疗方法。方法　回顾分析１６ 例先天性肌强直患者的临床特征。结果　本组７例（７／１６） 患者有遗传史,所有患者均有肌强直及肌肉肥大。肌电图均示肌强直电位。结论　遗传史、临床特征和肌电图是诊断本病的主要依据。     

Screening for mutations in Spanish families with myotonia. Functional analysis of novel mutations in CLCN1 gene

Myotonia congenita is an inherited muscle disorder caused by mutations in the CLCN1 gene, a voltage-gated chloride channel of skeletal muscle. We have studied 48 families with myotonia, 32 out of them carrying mutations in CLCN1 gene and eight carry mutations in SCN4A gene. We have found 26 different mutations in CLCN1 gene, including 13 not reported previously. Among those 26 mutations, c.180+3A>T in intron 1 is present in nearly one half of the Spanish families in this series, the largest one analyzed in Spain so far. Although scarce data have been published on the frequency of mutation c.180+3A>T in other populations, our data suggest that this mutation is more frequent in Spain than in other European populations. In addition, expression in HEK293 cells of the new missense mutants Tyr137Asp, Gly230Val, Gly233Val, Tyr302His, Gly416Glu, Arg421Cys, Asn567Lys and Gln788Pro, demonstrated that these DNA variants are disease-causing mutations that abrogate chloride currents.     

Functional consequences of chloride channel gene (CLCN1) mutations causing myotonia congenita

OBJECTIVE: To determine the functional consequences of missense mutations within the skeletal muscle chloride channel gene CLCN1 that cause myotonia congenita. BACKGROUND: Myotonia congenita is a genetic muscle disease associated with abnormalities in the skeletal muscle voltage-gated chloride (ClC-1) channel. In order to understand the molecular basis of this inherited disease, it is important to determine the physiologic consequences of mutations found in patients affected by it. METHODS: The authors used a mammalian cell (human embryonic kidney 293) expression system and the whole-cell voltage-clamp technique to functionally express and physiologically characterize five CLCN1 mutations. RESULTS: The I329T mutation shifted the voltage dependence of open probability of ClC-1 channels to the right by 192 mV, and the R338Q mutation shifted it to the right by 38 mV. In addition, the I329T ClC-1 channels deactivated to a lesser extent than normal at negative potentials. The V165G, F167L, and F413C ClC-1 channels also shifted the voltage dependence of open probability, but only by +14 to +20 mV. CONCLUSIONS: The functional consequences of these mutations form the physiologic argument that these are disease-causing mutations and could lead to myotonia congenita by impairing the ability of the skeletal muscle voltage-gated chloride channels to maintain normal muscle excitability. Understanding of genetic and physiologic defects may ultimately lead to better diagnosis and treatment of patients with myotonia congenita.     

Heterozygous CLCN1 mutations can modulate phenotype in sodium channel myotonia

Nondystrophic myotonias are characterized by muscle stiffness triggered by voluntary movement. They are caused by mutations in either the CLCN1 gene in myotonia congenita or in the SCN4A gene in paramyotonia congenita and sodium channel myotonias. Clinical and electrophysiological phenotypes of these disorders have been well described. No concomitant mutations in both genes have been reported yet. We report five patients from three families showing myotonia with both chloride and sodium channel mutations. Their clinical and electrophysiological phenotypes did not fit with the phenotype known to be associated with the mutation initially found in SCN4A gene, which led us to screen and find an additional mutation in CLCN1 gene. Our electrophysiological and clinical observations suggest that heterozygous CLCN1 mutations can modify the clinical and electrophysiological expression of SCN4A mutation.     

Truncating CLCN1 mutations in myotonia congenita: Variable patterns of inheritance

Introduction: Myotonia congenita due to protein truncating CLCN1 mutations is associated with variable patterns of inheritance. Methods: Three family kindreds are described, all of whom possess protein truncating mutations (Y33X, fs503X, R894X). One lineage also has coexistent R894X, A313T, and A320V mutations. Results: The Y33X mutation kinship has autosomal recessive inheritance and a severe phenotype when homozygous. The fs503X family has autosomal dominant inheritance and a moderate‐to‐severe phenotype. The A313T mutation kindred also has autosomal dominant inheritance but expresses a mild phenotype, except for the more severely affected compound heterozygotes. Conclusions: Early truncating mutations precluding dimerization are expected to be autosomal recessive and express a severe phenotype, while later mutations may be variable. The pedigrees presented here demonstrate that intrafamilial phenotypic variability may result from a dosage effect of an additional mutation, not necessarily variable expressivity. Mutations that have unexpected patterns of inheritance may represent allelic variability. Muscle Nerve 49:593–600, 2014     

Novel mutations in the muscle chloride channel CLCN1 gene causing myotonia congenita in Spanish families

Mutations in the muscular voltage-dependent chloride channel gene (CLCN1), located at 7q35, lead to recessive and dominant myotonia congenita. We report four novel mutations identified in this gene, after clinical, electromyographic, and genetic studies performed on 13 unrelated families. Two of the four mutations (2512insCTCA and A218T) were identified in families with Thomsen’s disease, one (Q658X) in a family with Becker’s disease, and the fourth (R669C) in a presumably sporadic patient with the Becker phenotype. Although identification of the mutations allows us to establish some genotype/phenotype correlations, this does not wholly account for the clinical heterogenity and the inheritance patterns of the disease. Received: 27 June 1998 Received in revised form: 11 November 1998 Accepted: 16 November 1998     

Identification of two novel compound heterozygous CLCN1 mutations associated with autosomal recessive myotonia congenita

ABSTRACT

Objectives: Myotonia congenita (MC) is a rare genetic muscular disorder caused by CLCN1 mutations, which codes for skeletal muscle chloride channel CLC1. MC is characterized by impaired muscle relaxation after contraction resulting in muscle stiffness. This study aimed to identify the genetic etiology of a Chinese family affected with recessive MC.

Methods: Whole exome sequencing was performed to identify the disease-associated variants. The candidate causal genes discovered by WES were then confirmed by Sanger sequencing and co-segregation analyses were also conducted.

Results: Two novel compound heterozygous mutations in CLCN1 gene, p.D94Y (paternal allele) and p.Y206* (maternal allele), were successfully identified as the pathogenic mutations by whole-exome sequencing (WES). The mutations were confirmed with Sanger sequencing in the family members and cosegregated with the MC phenotype. The two mutations have not been reported in the HGMD, dbSNP, 1000 Genomes project, ClinVar database, ExAC, and gnomAD previously. Mutation p.D94Y is predicted to be deleterious by using in silico tools and p.Y206* is a nonsense mutation, causing protein synthesis termination.

Conclusions: Molecular genetics analysis offers an accurate method for diagnosing MC. Our results expand the mutational spectrum of recessive MC.     

A novel CLCN1 mutation: P480T in a Japanese family with Thomsen's myotonia congenita

At least 50 disease-causing mutations in the skeletal muscle voltage-gated chloride channel gene (CLCN1), almost all of which originate from Caucasian families, have been identified. We investigated a Japanese family with Thomsen's myotonia congenita that included 16 affected individuals (8 men and 8 women) through five generations. Polymerase chain reaction (PCR)-single-strand conformation polymorphism (SSCP) screening of 11 members showed an aberrant conformer in exon 13 of CLCN1 complementary DNA (cDNA) in 8 affected and 1 unaffected members. By sequence analysis, we identified a C-to-A transition at nucleotide position 1438, resulting in a substitution of proline for threonine at amino acid position 480 (P480T), the same position of the original mutation (P480L) in Thomsen's disease. The P480T mutation was novel and absent in 100 normal controls. Seven of the 8 affected individuals were heterozygous; another, from affected parents, was homozygous. Clinically, myotonia in the homozygous patient was more severe than that in heterozygous patients, probably due to the gene dosage effect. On a long-train nerve-stimulation test at a rate of 3 Hz, M-wave responses in the homozygous patient showed marked decrement followed by recovery. In contrast, the heterozygous patients showed just a slight decrement or no changes, and none of 2 patients with myotonic muscular dystrophy or 2 normal controls revealed any decrement. Thus, the long-train nerve-stimulation test at a low stimulus frequency may be a useful tool to assess the disease-severity/genotype relationship in myotonia congenita.     

A Becker myotonia patient with compound heterozygosity for CLCN1 mutations and Prinzmetal angina pectoris

Becker myotonia is a recessive muscle disease with prevalence of > 1:50,000. It is caused by markedly reduced function of the chloride channel encoded by CLCN1. We describe a Polish patient with severe myotonia, transient weakness, and muscle cramps who only responds to lidocaine. In addition, the patient has Prinzmetal angina pectoris and multiple lipomatosis. He is compound heterozygeous for a novel p.W303X and a frequent p.R894X CLCN1 mutation. CLCN1 exon number variation was excluded by MLPA. His son with latent myotonia was heterozygeous for p.R894X. We discuss the potential relations of the three rare diseases and the inheritance of p.R894X.