SCN4A基因V781I突变与原发性低钾型周期性麻痹

目的明确SCN4A基因V781I突变是否为我国原发性低钾型周期性麻痹的相关突变。方法利用PCR-直接测序技术和酶切技术对1个低钾型周期性麻痹家系（3例患者和14名健康亲属）、71例散发性低钾型周期性麻痹患者以及100名健康人进行了SCN4A基因V781I突变的筛查。结果低钾型周期性麻痹家系中所有患者均存在此突变，且有4名健康亲属携带此突变（1名男性，3名女性）。71例散发性低钾型周期性麻痹患者中有7例存在此突变，100名健康人中也有7例存在此突变，该两组间V781I突变频率差异无统计学意义（X^2=0．452，P=0．502）。结论SCN4A基因V781I突变在低钾型周期性麻痹患者与健康人中的突变频率差异无统计学意义，此突变可能是正常基因多态性。     

正常血钾型周期性麻痹SCN4A基因新突变的检测

目的　报道正常血钾型周期性麻痹 (normoPP)一家系的临床特点 ,并筛查SCN4A基因以期发现有义突变。方法　提取知情同意的患者及部分家属外周血基因组DNA ,应用变性高效液相色谱分析 (DHPLC)技术筛查患者SCN4A基因全部 2 4个外显子 ,对发现异常者进行测序分析。结果先证者常规实验室检查未见异常 ,发作期肌酸激酶 (CK) 112 6U/L(正常值 <2 0 0U/L) ,肌电图正常。发作间期行肌肉活检未见显著异常。基因研究发现先证者及其父亲 (患者 )SCN4A基因发生同一新突变G2 10 1A ,并引起氨基酸序列改变Arg6 75Gln。该突变不同于目前发现的明确导致高钾型周期性麻痹(hyperPP)的突变 ,也不同于已知的SCN4A基因所有突变。结论　normoPP患者存在一新突变Arg6 75Gln ,该突变可能与疾病相关。     

骨骼肌钠通道α1亚基基因R1129Q新突变导致正常钾和低钾性周期性瘫痪一家系

目的 报道1个骨骼肌钠通道α1亚基(SCN4A)基因新突变导致的正常钾和低钾性周期性瘫痪家系的临床和病理改变特点.方法 本家系为常染色体显性遗传,共有9例患者,男性4例,女性5例,发病年龄7～25岁.5例患者为正常钾性周期性瘫痪,其中4例伴随肌强直症状;3例患者为低钾性周期性瘫痪;1例发作时血钾浓度不详.对先证者进行左肱二头肌活体组织检查.先证者和7例家系患者、3名无症状家系成员以及50名健康人行SCN4A基因测序.结果 先证者的肌纤维出现轻度肥大和萎缩,伴随核内移和肌纤维内空泡,部分肌纤维内氧化酶分布异常.所有患者均存在SCN4A基因的R1129Q突变,3名无症状家系成员以及50名健康对照无此突变.结论 SCN4A基因R1129Q新突变在同一家系内可以导致低血钾性和正常血钾性周期性瘫痪共存.     

骨骼肌钠通道α1亚基基因R1129Q新突变导致正常钾和低钾性周期性瘫痪一家系

目的 报道1个骨骼肌钠通道α1亚基(SCN4A)基因新突变导致的正常钾和低钾性周期性瘫痪家系的临床和病理改变特点.方法 本家系为常染色体显性遗传,共有9例患者,男性4例,女性5例,发病年龄7～25岁.5例患者为正常钾性周期性瘫痪,其中4例伴随肌强直症状;3例患者为低钾性周期性瘫痪;1例发作时血钾浓度不详.对先证者进行左肱二头肌活体组织检查.先证者和7例家系患者、3名无症状家系成员以及50名健康人行SCN4A基因测序.结果 先证者的肌纤维出现轻度肥大和萎缩,伴随核内移和肌纤维内空泡,部分肌纤维内氧化酶分布异常.所有患者均存在SCN4A基因的R1129Q突变,3名无症状家系成员以及50名健康对照无此突变.结论 SCN4A基因R1129Q新突变在同一家系内可以导致低血钾性和正常血钾性周期性瘫痪共存.     

A novel sodium channel mutation in a family with hypokalemic periodic paralysis

OBJECTIVE: To identify the cause of hypokalemic periodic paralysis (HOKPP) in a family whose disease is not caused by a mutation in the dihydropyridine-sensitive (DHP) receptor alpha1-subunit gene (CACNA1S). BACKGROUND: Hypokalemic periodic paralysis is primarily caused by mutations within CACNA1S. Genetic heterogeneity for HOKPP has been reported, but no other locus has been identified. METHODS: Single-stranded conformational polymorphism (SSCP) analysis and PCR direct sequencing were used to screen the skeletal muscle alpha1-sodium channel gene (SCN4A) for a mutation in our family. RESULTS: SSCP analysis showed an abnormally migrating conformer in exon 12. Direct sequencing of the conformer showed a guanine to adenine transition at position 2006 in the cDNA sequence; this results in an amino acid substitution of a highly conserved arginine (Arg) to histidine (His) at position 669. This sequence alteration segregated only with the affected members of the kindred and was not found in a panel of 100 DNA samples from healthy controls. The amino acid substitution alters the outermost positive charge in the membrane spanning segment DII/S4, which is involved in voltage sensing. CONCLUSIONS: The first arginine in DII/S4 and in DIV/S4 within the skeletal muscle sodium channel and the L-type calcium channel genie CACNA1S appear to be critical for normal function. In all four cases, Arg to His mutations result in a disease phenotype. The identification of a mutation within the skeletal muscle sodium channel resulting in hypokalemic periodic paralysis represents a novel finding.     

Muscle weakness in a Japanese family of Arg1239His mutation hypokalemic periodic paralysis

Familial hypokalemic periodic paralysis is an autosomal dominant disorder. Recently, three predominant mutations were found in the muscle dihydropyridine-sensitive calcium channel alpha 1-subunit gene. We present a Japanese family that displays one of these, the Arg1239His mutation. All the affected individuals of this family displayed this mutation. Two cases had a history of recurrent episodes of muscle weakness and difficulty in running before their first paralytic attack. It is suggested that there are no racial differences with this mutation, and that mild muscle weakness occurs not only after but also preceding the first attack.     

Mutation analysis of two patients with hypokalemic periodic paralysis and suspected malignant hyperthermia

Hypokalemic periodic paralysis (HypoPP) and malignant hyperthermia (MH) are autosomal-dominant genetically heterogeneous ion channelopathies. MH has been described in patients with HypoPP, suggesting a potential link between these disorders. However, a common genetic determinant has not been described. With the aim of corroborating this association, four candidate genes were screened in two independent HypoPP patients, one of whom was also diagnosed as MH-susceptible and the other as MH-normal by the in vitro contracture test (IVCT). An A>G change at nucleotide 7025 was detected in the RYR1 gene in the HypoPP/MH-susceptible patient. Detection of the same mutation in three independent MH families suggested that 7025A>G represents a novel MH-susceptibility allele and that MH and HypoPP occurred independently in the case presented. Conclusive evidence in support of the hypothesis that MH and HypoPP are allelic was therefore not obtained.     

运动诱发试验在低钾型周期性麻痹诊治中的应用

目的:探讨运动诱发试验(exercise test,ET)在低钾型周期性麻痹中的诊断价值及相关影响因素.方法:对我院门诊确诊低钾型周期性麻痹的30例患者,在发作期检查肌力、血清钾(K+)、肌酸激酶(CK)、甲状腺功能,发作间期复查肌力、K+、CK值,并进行ET测定.同时选择30例健康人作为对照组.结果:发作期K+值的高低与肌力改变呈正相关,与CK值的高低呈负相关.发作间期行ET,30例患者波幅逐渐下降 (45.56%±19.91%),其波幅减低百分比显著大于对照组(P=0.001).ET波幅变化百分比与肌力、K+、CK水平无明显相关性.结论:ET可作为低钾型周期性麻痹发作间期的重要辅诊方法.ET阳性与发病机制有关,与起病形式、严重程度无相关性.     

Mutations associated with hypokalemic periodic paralysis: from hotspot regions to complete analysis of CACNA1S and SCN4A genes

neurogenetics - Familial periodic paralyses (PPs) are inherited disorders of skeletal muscle characterized by recurrent episodes of flaccid muscle weakness. PPs are classified as hypokalemic...     

A Japanese family of autosomal dominant hypokalemic periodic paralysis with a CACNL1A3 gene mutation

Recent genetic research revealed that hereditary periodic paralysis is an ion-channel disorder. Genetic linkage analysis has mapped the autosomal dominant hypokalemic periodic paralysis (HypoPP) locus to chromosome 1q31–32, where the dihydropyridine sensitive calcium channel α₁ subunit (CACNL1A3) is located. Subsequently, two predominant missense point mutations were found in the CACNL1A3 gene. Both mutations substitute arginine to histidine (Arg528Ilis and Arg1239His). The Arg528His mutation is characterized by incomplete penetrance in females, whereas Arg1239His is not. We analyzed Japanese hypokalemic periodic paralysis patients (familial, sporadic and thyrotoxic), and detected the Arg528His mutation in one HypoPP family. This family shows more severe symptoms in successive generations and the severity of the symptoms is higher in males than in females within the same family.     

Lower-extremity magnetic resonance imaging in patients with hyperkalemic periodic paralysis carrying the SCN4A mutation T704M: 30-month follow-up of seven patients

Hyperkalemic periodic paralysis (hyperKPP) is a muscle channelopathy characterized by recurrent paralytic attacks. Our previous study, in which we conducted whole-body muscle magnetic resonance imaging (MRI) in patients with hyperKPP, revealed muscle atrophy and fatty change in the lower extremity, especially in older persons. The aim of current study was to identify the progression of myopathy in hyperKPP patients had been assessed in the previous study. We performed lower-extremity muscle MRI in seven hyperKPP patients carrying the T704M mutation in the SCN4A gene at an interval of 30 months. Muscle atrophy, edematous change, fatty change, and fat fraction quantified using the Dixon technique were compared with the previous MRI findings. The lower-extremity MRI scan showed progressive muscle pathologic findings when compared with the previous study. Muscle atrophy, edematous change, and fatty change were prominent in the superficial posterior compartment of the lower leg. The follow-up lower-extremity muscle MRI findings provide evidence for chronic progressive myopathy and suggest the usefulness of MRI for assessing disease progression in patients with hyperKPP. This study is meaningful in terms of providing data showing the longitudinal changes of muscles in patients with periodic paralysis.     

家族性高钾型周期性麻痹的SCN4A基因突变

目的　筛查1个高钾型周期性麻痹(hyperkalemicperiodicparalysis, hyperKPP)家系的SCN4A基因,明确该病与SCN4A基因的关系。方法　总结1个hyperKPP家系中7例患者的临床特点,应用变性液相色谱(denaturinghighperformanceliquidchromatography,DHPLC)技术筛查SCN4A基因全部24个外显子,对发现异常洗脱峰者进行连锁分析并测序。结果　该家系具有典型hyperKPP临床特征,但无肌强直。先证者经DHPLC筛查发现在外显子13、23及24存在杂合二倍体。测序及连锁分析证实位于外显子13的碱基替换引起氨基酸序列改变(Thr704Met);外显子23的碱基替换虽引起氨基酸序列改变(Asp1376Asn)与疾病连锁,但进一步研究显示其为一良性多态;外显子24的碱基替换为同义突变。结论　该家族性hyperKPP与SCN4A基因相关,并由最常见的突变Thr704Met引起。     

Severe prognosis in a large family with hypokalemic periodic paralysis

Hypokalemic periodic paralysis (HypoPP) is a channel disorder caused primarily by mutations in the human skeletal muscle alpha1 subunit (CACNA1S) of the dihydropyridine-sensitive calcium channel. Molecular, clinical, and biochemical studies were aimed at establishing genotype/phenotype correlations in a large Italian family affected by a severe form of HypoPP. Whereas patients with HypoPP usually show a normal life span, in this family three male patients died young, one of them from anesthetic complications resembling malignant hyperthermia. Our patients carried the c1583G>A genetic lesion (R528H), which has been associated with a mild phenotype and with incomplete penetrance in women. Surprisingly, the R528H amino acid substitution in the family presented here correlated with an unfavorable prognosis in both male and female patients. We conclude that genetic characterization is an important requirement to alert physicians about the management of similar patients, especially when anesthesia is considered.