脊髓性肌萎缩症的发病机制及诊治的研究进展

脊髓性肌萎缩症是一组常见的常染色体隐性遗传病，以脊髓前角运动神经元退行性变而导致的进行性、对称性肌萎缩和肌张力减低为临床特征。共分为4种类型即脊髓性肌萎缩症Ⅰ、Ⅱ、Ⅲ和Ⅳ型，其临床诊断主要依赖于临床表现、家族遗传史、实验室检查及基因检测。文中对脊髓性肌萎缩症的发病机制及诊治进展进行综述。     

脊髓性肌萎缩症治疗临床研究进展

脊髓性肌萎缩症为常染色体隐性遗传性神经肌肉病,以脑干和脊髓运动神经元变性引起的进行性肌无力和肌萎缩为特征,是临床常见的婴儿致死性遗传性神经肌肉病。运动神经元生存1(SMN1)基因突变致SMN蛋白缺乏为其发病机制,深入了解疾病发病机制的分子学基础,以促进包括反义寡核苷酸、腺相关病毒介导的SMN1基因替代疗法、上调SMN蛋白表达的口服小分子药物,以及肌肉激活药物、神经保护药物等新兴特异性治疗方法的研发,降低病死率、改善患者生活质量。     

运动神经元病81例临床分析

目的:对运动神经元病的临床特点,分型及诊断标准进行分析。方法:总结81例运动神经元病的临床及辅助检查资料。结果:本病多见于50岁以上,平均发病年龄为53.86±14.14;以肌萎缩性侧索硬化症和进行性脊肌萎缩症多见;肌肉无力和/或肌肉萎缩及锥体柬征为最常见的临床体征;误诊率高,易误诊为颈、脊髓病。结论:本病是一组老年前期和老年期多发的慢性进行疾病,误诊率高,诊断本病时应密切联系临床发展过程。     

福建医科大学附属第一医院神经内科关于脊髓性肌萎缩症的研究论文在Archives of Neurology上发表

儿童型脊髓性肌萎缩症（SMA）是一类较常见的常染色体隐性遗传病，目前尚无有效的治疗方法，死亡率及致残率均较高。其致病基因运动神经元生存基因（SMN）存在两种同源性极高的拷贝SMN1、SMN2，90％以上患者存在SMN1基因缺失，可通过判断有无SMN1缺失来进行基因诊断。目前常用的基因诊断及产前诊断方法有连锁分析、限制性片段长度多态性（RFLP）、变性高效液相色谱（DHPLC）、     

进行性脊髓性肌萎缩症的临床和基因研究

进行性脊髓性肌萎缩症的临床和基因研究麻宏伟王阳宓真武盈玉赵淑霞赵颇脊髓性肌萎缩（ＳＭＡ）国外发病率为１／１００００。国内至９０年代已达１８０余例，其中儿童时期诊断的病例约为１／３。多以临床和肌肉病理确诊，尚没有基因研究的资料。我们近两年观察了４例ＳＭ...     

脊髓性肌萎缩症单细胞巢式聚合酶链反应技术的建立及初步应用

目的 建立单细胞巢式聚合酶链反应技术,并探讨进行脊髓性肌萎缩症基因诊断的可行性,为植入前遗传学诊断奠定基础.方法 应用显微操作技术从外周血中分离单个淋巴细胞,制备单细胞DNA模板.分别应用巢式聚合酶链反应和引物延伸预扩增两种方法扩增正常对照者外周血中单个淋巴细胞运动神经元生存(SMN)基因第7、8号外显子,计算其阳性率,建立SMN1基因的单细胞巢式聚合酶链反应技术.并应用该项技术及限制性酶切对1例脊髓性肌萎缩症患者进行基因诊断.结果 正常对照者巢式聚合酶链反应共扩增60个外周血单个淋巴细胞SMN1基因第7号外显子,其中54个扩增成功,阳性率为90%;引物延伸预扩增共扩增10个外周血单个淋巴细胞,巢式聚合酶链反应分别扩增SMN1基因第7、8号外显子,在20个聚合酶链反应扩增中共有17个单个淋巴细胞扩增成功,阳性率为85%.应用巢式聚合酶链反应和引物延伸预扩增两种方法对1例脊髓性肌萎缩症患者单个淋巴细胞扩增后经限制性酶切显示SMN1基因缺失,结果与全血基因组聚合酶链反应-限制性酶切一致.结论 巢式聚合酶链反应和引物延伸预扩增方法各有优缺点,巢式聚合酶链反应耗时短、操作简便,可作为脊髓性肌萎缩症患者单细胞基因诊断的首选方法.     

应用多重连接依赖性探针扩增技术进行脊髓性肌萎缩症产前诊断

目的 探讨多重连接依赖性探针扩增技术在脊髓性肌萎缩症产前诊断中的临床应用价值.方法 以脊髓性肌萎缩症6个家系作为研究对象.包括患者7例、父母12名、胎儿6例.采用多重连接依赖性探针扩增技术对运动神经元生存(SMN)基囚及脊髓性肌萎缩症修饰基因进行分析,应用聚合酶链反应-限制性酶切片段长度多态性技术检测SMNI基凶缺失,羊水标本分别通过直接离心沉淀和细胞培养进行DNA分析.结果 多重连接依赖性探针扩增分析提示6个家系中7例患者及1例胎儿(家系Ⅳ)呈SMNI基凶纯合缺失,与聚合酶链反应.限制性酶切片段长度多态性分析结果一致;11名父母及5例胎儿的SMNI拷贝数为1,1名母亲(家系V)SMNI拷贝数为2,均为脊髓性肌萎缩症携带者.多重连接依赖性探针扩增分析显示.6个家系中10名成员SMN2拷贝数为1,15名成员SMN2拷贝数为2;多重连接依赖性探针扩增分析.6个家系中3名成员神经元凋亡抑制蛋白(NAIP)基冈缺失,其余家系成员正常.结论 多重连接依赖性探针扩增技术为一快速而可靠的基凶榆测及定量分析方法,可准确检测SMN基凶及脊髓性肌萎缩症修饰基凶的缺失突变并分析基因拷贝数,适用于脊髓性肌萎缩症患者、携带者的基因诊断及产前诊断.     

肌萎缩侧索硬化症的病因学与实验模型研究进展

肌萎缩侧索硬化症(amyotrophic lateral sclerosis, ALS)与脊髓性肌萎缩、进行性球麻痹和原发性侧索硬化症同属运动神经元病.其病变主要侵犯脊髓前角细胞、脑干运动神经核及锥体束,临床特征表现为上、下运动神经元同时受损[1].其病因复杂,治疗困难,为神经系统疾病研究热点之一,本文就ALS病因学与实验模型研究进展做一介绍.     

进行性脊髓性肌萎缩症的基因诊断研究

目的 建立进行性脊髓性肌萎缩症（ＳＭＡ）的特异性基因诊断方法。方法 采用不对称聚合酶链反应（ＰＣＲ）方法扩增运动神经元生存（ＳＭＮ）基因，并结合单链构象多态性（ＳＳＣＰ）分析方法分析该基因的变异和缺失。     

青年上肢远端肌萎缩症的临床肌电图及肌肉病理的研究

对２２例青年上肢远端肌萎缩症的临床，肌电图及肌肉病理进行了研究。肌电图显示神经源性损害，主要分布于病侧手肌，对侧手肌也可有亚临床电生理异常，提示受损节段多在颈７、８－胸１脊髓前角，肌肉组织病理，酶组织化学及电镜检查显示神经源性肌萎缩，为下颈髓前角细胞受损的结果有别于运动神经元病，其病因可能与局部脊髓血循环境障碍有关。     

Spinal muscular atrophy genotyping by gene dosage using multiple ligation-dependent probe amplification

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by degeneration of the anterior horn cells of the spinal cord, causing symmetric proximal muscle weakness. SMA is classified in three clinical types, SMA I, SMA II, and SMA III, based on the severity of the symptoms and the age of onset. About 95% of SMA cases are caused by homozygous deletion of the survival motor neuron 1 (SMN1) gene (5q13), or its conversion to SMN2. The molecular diagnosis of this disease is usually carried out by a polymerase chain reaction–restriction fragment length polymorphism approach able to evidence the absence of both SMN1 copies. However, this approach is not able to identify heterozygous healthy carriers, which show a very high frequency in general population (1:50). We used the multiple ligation-dependent probe amplification (MLPA) approach for the molecular diagnosis of SMA in 19 affected patient and in 57 individuals at risk to become healthy carriers. This analysis detected the absence of the homozygous SMN1 in all the investigated cases, and allowed to discriminate between SMN1 deletion and conversion to SMN2 on the basis of the size showed by the peaks specific for the different genes mapped within the SMA critical region. Moreover, MLPA analysis evidenced a condition of the absence of the heterozygous SMN1 in 33 out of the 57 relatives of the affected patients, demonstrating the usefulness of this approach in the identification of healthy carriers. Thus, the MLPA technique represents an easy, low cost, and high throughput system in the molecular diagnosis of SMA, both in affected patients and in healthy carriers.     

Correlation between SMA type and SMN2 copy number revisited: An analysis of 625 unrelated Spanish patients and a compilation of 2834 reported cases

Spinal muscular atrophy (SMA) is a neuromuscular disorder caused by loss or mutations in SMN1. According to age of onset, achieved motor abilities, and life span, SMA patients are classified into type I (never sit), II (never walk unaided) or III (achieve independent walking abilities). SMN2, the highly homologous copy of SMN1, is considered the most important phenotypic modifier of the disease. Determination of SMN2 copy number is essential to establish careful genotype–phenotype correlations, predict disease evolution, and to stratify patients for clinical trials. We have determined SMN2 copy numbers in 625 unrelated Spanish SMA patients with loss or mutation of both copies of SMN1 and a clear assignation of the SMA type by clinical criteria. Furthermore, we compiled data from relevant worldwide reports that link SMN2 copy number with SMA severity published from 1999 to date (2834 patients with different ethnic and geographic backgrounds). Altogether, we have assembled a database with a total of 3459 patients to delineate more universal prognostic rules regarding the influence of SMN2 copy number on SMA phenotype. This issue is crucial in the present scenario of therapeutic advances with the perspective of SMA neonatal screening and early diagnosis to initiate treatments.     

Mutations of the LMNA gene can mimic autosomal dominant proximal spinal muscular atrophy

The molecular basis of autosomal dominant spinal muscular atrophy (AD-SMA) is largely unknown. Because the phenotypic spectrum of diseases caused by LMNA mutations is extremely broad and includes myopathies, neuropathies, and cardiomyopathies designated as class 1 laminopathies, we sequenced the LMNA gene in index patients with the clinical picture of proximal SMA, who had a family history suggestive of autosomal dominant inheritance. Among the 19 families investigated, two showed pathogenic mutations of the LMNA gene, resulting in the diagnosis of a class 1 laminopathy in about 10% of our series. We found one novel truncating mutation (c.1477C > T, Q493X) and one previously described missense mutation (c.1130G > T, R377H) in the LMNA gene of two unrelated patients with adult-onset proximal SMA followed by cardiac involvement 14 and 22 years after the onset of weakness. The pedigrees of both families revealed a high frequency of cardiac abnormalities or sudden deaths. Our findings extend the spectrum of laminopathies and are of relevance for genetic counseling and clinical care of families presenting with adult-onset proximal SMA. Particularly, if neurogenic atrophy is combined with a cardiac disease in a family, this should prompt LMNA mutation analysis.     

Spinal muscular atrophy combined with sporadic olivopontocerebellar atrophy

The combination of spinal muscular atrophy (SMA) with a variety of neural and extraneural defects, particularly pontocerebellar hypoplasia, has been reported. To date, all of the reported SMA with pontocerebellar hypoplasia was from infants; however, here we report a SMA with sporadic olivopontocerebellar atrophy (sOPCA) in an adult patient. The 68-year-old male patient displayed various clinical symptoms including progressive proximal muscle weakness, muscle atrophy and muscle fasciculation with a long course of disease. EMG demonstrated that amyotrophy was due to the impairment of lower motor neurons. The clinical symptoms and the EMG were consistent with the diagnosis of SMA. The presence of cerebellar ataxia, limb tremors, muscle atrophy and weakness in the patient led to the diagnosis of sOPCA that was confirmed by the MRI results. To our knowledge, this is the first case report of combination of SMA with sOPCA in an adult. It is yet unclear whether there is a common pathogenesis between the two diseases.     

Differential diagnosis between amyotrophic lateral sclerosis and spinal muscular atrophy by skin involvement

Amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA) might be clinical variants caused by the same etiology, or different diseases altogether. We studied the skin in 12 patients with ALS and 7 patients with SMA. The "delayed return phenomenon" (DRP) was observed only in ALS patients. On light microscopy, collagen bundles in ALS dermis were seen to be less numerous, thinner and more loosely woven than in SMA. Electron microscopy revealed that in ALS (1) collagen fibers became thinner as the disease lasted longer, and (2) collagen bundles were separated by much more amorphous material. These findings were not observed in SMA. Our observations show that ALS may be distinguished from SMA by the presence of abnormal dermal collagen. Therefore, we suggest that comparable clinical and pathological skin analysis is the most important diagnostic tool in differentiating between ALS and SMA.     

A natural history study of late onset spinal muscular atrophy types 3b and 4

Background   Spinal muscular atrophy (SMA) is caused by a homozygous deletion of the survival motor neuron (SMN)1 gene. The nearly identical SMN2 gene plays a disease modifying role. SMA is classified into four different subtypes based on age of onset and clinical course (SMA types 1–4). The natural history of early onset SMA types 1–3a has been studied extensively. Late onset SMA is rare and disease course has not been studied in detail. Objective   To perform a prospective study on the clinical course and the correlation with SMN2 copy numbers of late onset SMA. Methods   Patients fulfilling the diagnostic criteria for late onset SMA (types 3b and 4) were included in the study. At inclusion and follow-up, muscle strength, respiratory function, functional status and quality of life were assessed. SMN2 copy number was determined in all patients. Results   Twelve patients were identified and included. Six patients were siblings from one family, two patients were brothers from a second family and four patients were sporadic cases. All patients carried four copies of the SMN2 gene. Median age of disease onset was 22.2 years (10–37). Age of disease onset in patients from family one was lower as compared to the other patients. None of the outcome measures changed after a follow-up of 2.5 years. Five patients reported an increase in fatigue and muscle weakness. None of the patients showed symptoms of respiratory insufficiency. Conclusions   This study indicates that late onset SMA is not characterized by disease progression and that alternative or surrogate disease markers are required for the design of future trials. This study confirms the finding that SMN2 copy number is a SMA disease course modifier.     

The effect of hydroxyurea in spinal muscular atrophy cells and patients

BACKGROUND: Spinal muscular atrophy (SMA) is a degenerative motor neuron disease caused by homozygous mutations of the survival motor neuron 1 (SMN1) gene. Effective treatment for SMA is unavailable at present. The aim of this study was to investigate the effect of hydroxyurea (HU) in SMA cells and patients. MATERIALS AND METHODS: Fifteen SMA lymphoid and three fibroblast cell lines, 2 from SMA patients and 1 control, were treated with HU at different concentrations, and 33 patients (types II, III) randomized into three groups on different HU dosage, 20, 30, 40 mg/kg/day, were treated for 8 weeks and followed up for another drug-free 8 weeks. The effect of HU on SMN2 gene expression and clinical manifestations was evaluated. RESULTS: After treatment, in vitro, full-length mRNA level and gems number increased significantly, and hnRNP A1 protein decreased. In vivo, there were slight increases in muscle strength scores at 4 weeks and full-length SMN mRNA at 8 weeks in 30 mg/kg/day subgroup. CONCLUSIONS: Treating with HU enhanced SMN2 gene expression in SMA cells and showed slight trend towards improvement in some clinical outcome measures in SMA patients which suggests HU may be safe to use in SMA patients but larger randomized, placebo-controlled, double-blind trials are needed to further investigate its efficacy.     

Spinale Muskelatrophie

The most common neurodegenerative disease in childhood is spinal muscular atrophy (SMA). The severe infantile type 1 (Werdnig-Hoffman disease) makes 60% of SMA in total. These children usually die within 18 months without ventilation. New therapeutic approaches have led from the theoretical concept to randomized controlled clinical trials in patients. For the first time, a pharmacological treatment of SMA has been approved. The early detection of the disease is decisive for the success of therapy. All previous data suggest starting treatment early and when possible prior to the onset of symptoms considerably improves the outcome in comparison to a delayed start. The goal must be the presymptomatic diagnosis in order to initiate treatment before motor neuron degeneration. Technical and ethical prerequisites for a molecular genetic newborn screening are given.     

Combination of SMN2 copy number and NAIP deletion predicts disease severity in spinal muscular atrophy

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disorder caused by mutations in the SMN1 gene. The SMN2 gene is highly homologous to SMN1 and has been reported to be correlated with severity of the disease. The clinical presentation of SMA varies from severe to mild, with three clinical subtypes (type I, type II, and type III) that are assigned according to age of onset and severity of the disease. Here, we aim to investigate the potential association between the number of copies of SMN2 and the deletion in the NAIP gene with the clinical severity of SMA in patients of Malaysian origin. Forty-two SMA patients (14 of type I, 20 type II, and 8 type III) carrying deletions of the SMN1 gene were enrolled in this study. SMN2 copy number was determined by fluorescence-based quantitative polymerase chain reaction assay. Twenty-nine percent of type I patients carried one copy of SMN2, while the remaining 71% carried two copies. Among the type II and type III SMA patients, 29% of cases carried two copies of the gene, while 71% carried three or four copies of SMN2. Deletion analysis of NAIP showed that 50% of type I SMA patients had a homozygous deletion of exon 5 of this gene and that only 10% of type II SMA cases carried a homozygous deletion, while all type III patients carried intact copies of the NAIP gene. We conclude that there exists a close relationship between SMN2 copy number and SMA disease severity, suggesting that the determination of SMN2 copy number may be a good predictor of SMA disease type. Furthermore, NAIP gene deletion was found to be associated with SMA severity. In conclusion, combining the analysis of deletion of NAIP with the assessment of SMN2 copy number increases the value of this tool in predicting the severity of SMA.