脊髓性肌萎缩症临床诊断研究进展

脊髓性肌萎缩症系由脊髓前角运动神经元退行性变而导致的进行性、对称性肌无力和肌萎缩的一类常染色体隐性遗传性疾病,其致病基因为运动神经元生存(SMN1)基因。临床上共分为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。目前尚无有效治疗方法,因此产前诊断和对基因携带者的筛查为有效预防措施。     

The use of non-typical materials as a source of DNA in post-mortem diagnosis of spinal muscular atrophy

BACKGROUND AND PURPOSE: Patients affected with SMA I usually die in early childhood before the end of the second year of life. Clinical diagnosis is often doubtful--without any molecular verification--and isolated DNA is not available. In such cases predicting the outcome of consecutive pregnancies is not possible. It appears, however, that the families often keep some relics of the diseased child, such as milk teeth, and pieces of umbilical cord; a dried drop of blood used for the Guthrie test in newborn screening may be available. The aim of this study was the post mortem molecular diagnosis of SMA based on samples of DNA isolated from such remnants. MATERIAL AND METHODS: PCR technique was applied to amplify exons 7 and 8 of SMN gene; DraI and DdeI restriction enzymes were used to distinguish SMN1/SMN2 genes. RESULTS: The deletion of the SMN gene was found using DNA isolated from (1) a blot of dried blood, (2) a milk tooth and (3) dried umbilical cord of children who died several years ago without the molecular verification of the suspected SMA. In one case the analysis of DNA obtained from umbilical cord did not confirm the diagnosis of SMA. CONCLUSIONS: Our results showed that biological materials such as those mentioned above may be kept for a long period of time without degradation of DNA, which is still satisfactory for molecular diagnosis of SMA. This is very important for genetic counseling and offering a prenatal test to the families concerned.     

Clinical and molecular diagnosis of spinal muscular atrophy

The spinal muscular atrophies are a group of disorders characterized by flaccid limb weakness. It is necessary to differentiate these from other causes and identify the SMA variants. In classical SMA, majority of the patients shows homozygous deletion of the telomeric SMN gene (SMN1) on chromosome 5q. The availability of DNA analysis has allowed proper genetic counseling and prenatal diagnosis in the affected families. Application of newer techniques has enabled more accurate carrier detection. Our objective is to stress the variability in the clinical features and recent advances in the molecular diagnosis for SMA.     

脊髓性肌萎缩症的基因诊断

我们运用错配 PCR- RFLP方法对脊髓性肌萎缩症 ( SMA)患者和对照组进行了基因诊断的研究。结果发现临床诊断为 SMA的患儿 10例中有 9例出现端粒 SMN基因缺失而确认为阳性 ,1例阴性 ;正常家系成员 2 0例及正常对照组 2 0例均为阴性。此与国外报道相符。该法特异性高、敏感性好 ,实用可靠 ,适用于 SMA的基因诊断和胎儿的产前诊断     

Epidemiological investigation of spinal muscular atrophy in Japan

BackgroundInternational reporting of epidemiological surveys of spinal muscular atrophy (SMA) in Japan has been limited to Shikoku, despite the epidemiology of the disease in countries worldwide becoming clearer. Treatments of 5q-SMA have been developed, and epidemiological studies are needed.PurposeThis study aimed to conduct a nationwide epidemiological survey of SMA in Japan to clarify the actual situation of SMA in Japan.MethodPatients with all clinical types of SMA, including neonates and adults, were selected from 1,005 medical facilities in Japan.ResultsAs of December 2017, the actual number of reported patients with SMA was 658 and the genetic testing rate was 79.5%. The estimated number of patients was 1,478 (95% confidence interval (CI), 1,122–1,834), with a prevalence of 1.17 (95%CI, 0.89–1.45) per 100,000 people and an incidence of 0.51 (95%CI, 0.32–0.71) per 10,000 live births. Incidence rates of 5q-SMA by clinical type were 0.27 (95%CI, 0.17–0.38) and 0.08 (95%CI, 0.04–0.11) per 10,000 live births for type 1 and 2, respectively, in cases with a definitive diagnosis by genetic testing. We found that 363 cases (82.7%) occurred less than 2 years and 88 (20.0%) occurred age of 2 months old or under.ConclusionThis study clarifies the prevalence and incidence of SMA in Japan. As infantile onset accounts for most cases of SMA, newborn screening and subsequent treatment are important to save lives.     

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.     

Confirmation of clinical diagnosis in requests for prenatal prediction of SMA type I.

The recent discovery of a major SMA-locus in the chromosomal region 5q makes it possible to carry out prenatal DNA studies in families in which a child with SMA type I has been born. Since direct mutation analysis is not yet possible, the reliability of prenatal prediction of SMA type I usually depends on the certainty of the clinical diagnosis in the index patient. Sixteen requests were received for DNA studies in couples who had had a previous child with SMA type I. After re-evaluation, the performance of prenatal diagnosis was rejected in four cases. Among the other twelve families prenatal DNA analysis of chorion villus biopsies has been carried out in three families. In all three cases the fetus had inherited the high-risk haplotypes from both parents, and the parents chose to terminate the pregnancy. An illustration of the prenatal DNA studies in one family is given. The importance of confirmation of the diagnosis SMA type I before performing DNA studies is emphasised.     

Duchenne muscular dystrophy: high frequency of deletions

DNA probes are available for Duchenne muscular dystrophy (DMD) carrier detection and prenatal diagnosis. With probes for about 25% of the proximal portion of the gene, we found the proximal probes detected deletions in 23% of nonselected DMD boys, while a single distal probe detected 17% more as deletions. The combined percentage was 39% for all probes tested. Prenatal diagnosis and carrier detection are more accurate if deletions are mapped rather than by use of restriction fragment length polymorphism analysis. The effort involved in screening all affected boys for deletions is considerably less, and provides an accurate genetic marker for subsequent prenatal diagnosis in the family and prospective counseling for female relatives. It seems likely that, once the entire gene (cDNA) is available for screening, most DMD boys will show deletions.     

Genetic neuromuscular disorders: what is the best that we can do?

The major advances in genetic neuromuscular disorders in the last 30 years have been: (a) identification of the genetic basis for hundreds of these disorders, (b) through knowing the genes, understanding their pathobiology and (c) subsequent implementation of evidence-based treatments for some of the disorders. New genomic technologies are providing precision diagnosis, mode of inheritance and likely prognosis for more patients than ever before. Parents of children with a genetic diagnosis can then use preimplantation or prenatal diagnosis to avoid having further affected children if they wish. But is this the best we can do for genetic neuromuscular disorders? Since the 1980s, it has been argued it would be better to identify Duchenne muscular dystrophy carrier mothers, rather than diagnose their affected sons. Carrier screening for recessive disorders can identify couples with a high chance of having affected children. It allows couples reproductive choice and can prevent infant morbidity and mortality and significant distress for families. Professional bodies in many countries now recommend prospective parents should be informed about carrier screening. Implementing and funding expensive therapies increases the cost-effectiveness of carrier screening, increasing its attractiveness to governments. Best practice for genetic neuromuscular disorders should include equitable access to carrier screening.     

Newborn screening for SMA in Southern Belgium

Approval was recently granted for a new treatment for spinal muscular atrophy (SMA). Given that the treatment is effective when administered early and the societal burden of SMA-related disability, the implementation of a newborn screening program is warranted. We describe the stepwise process that led us to launch a newborn screening program for SMA in Southern Belgium. Different political, ethical, and clinical partners were informed about this project and were involved in its governance, as were genetic and screening labs. We developed and validated a newborn screening method to specifically recognize homozygous deletions of exon 7 in the SMN1 gene. Subsequently, a 3-year pilot study has been recently initiated in one Belgian neonatal screening laboratory to cover 17.000 neonates per year. Coverage extension to all of Southern Belgium to screen 55.000 babies each year is underway.     

Prenatal diagnosis and management of fetal hydrocephaly and lissencephaly

Two cases of prenatal diagnosis of lissencephaly are presented in the context of a series of 118 cases of prenatally diagnosed hydrocephalus. Within this series there was one case of Walker-Warburg syndrome and another of Miller-Dieker syndrome. It is stressed that the cases reported here of ventriculomegaly diagnosed in utero show a very different outcome from those in published studies of fetal hydrocephalus which only deal with patients in whom the diagnosis was determined after birth. In those postnatal series there is a considerable selection bias, and the fate of the fetuses reported here was much worse than in postnatal series. Of the 118 fetuses 6 had fetal infections, 6 had chromosomal abnormalities, 26 had associated spina bifida, 64 fetuses had associated other anomalies, and only 28 had isolated hydrocephalus. Although it is difficult to determine the prognosis individually after prenatal diagnosis of ventriculomegaly, the data presented here may be helpful in counseling parents prenatally. The counseling should be performed with the collaboration of obstetricians, pediatricians, surgeons, and geneticists.Presented at the Symposium on Lissencephaly and Related Disorders, Münster, Germany, 13 July 1992     

Infectious diseases as causes of mental retardation and other concomitant neurological sequelae

Infectious diseases were regarded as alone to cause mental retardation in 11.1 percent and together with other aetiological factors in a further 1.5 percent of 1000 patients examined. In the former group prenatal infections including toxoplasmosis, rubella, influenza with drugs, and syphilis accounted for 18.0 percent, while perinatal and postnatal infections including pneumococcal, tuberculous and meningococcal meningitis as well as pertussis, measles, influenza and postvaccinal encephalitis, gastroenteritis with dehydration, and encephalitis due to unidentified organism accounted for 82.0 percent of such cases. A majority of these patients had profound mental retardation, epilepsy, and cerebral palsy. By the end of December 1988 one HIV-positive mentally retarded child was diagnosed in Finland. He was adopted abroad. In addition, two legal abortions and one healthy child were registered to HIV-infected Finnish mothers. The early diagnosis of underlying prenatal, perinatal or postnatal infectious diseases leading to mental retardation is emphasized in order to take care of the health of developing individuals along with to prevent this type of mental retardation.     

Molecular analysis and prenatal prediction of spinal muscular atrophy in Chinese patients by the combination of restriction fragment length polymorphism analysis, denaturing high-performance liquid chromatography, and linkage analysis

BACKGROUND: The difficulties and incurability of spinal muscular atrophy (SMA) highlight the importance of prenatal diagnosis in families with SMA. However, the system applied in prenatal screening is far from perfect. OBJECTIVES: To optimize the molecular assays and establish a relatively perfect system for prenatal screening. Design, Setting, and Patients A total of 87 patients and 132 parents from 77 families with SMA were screened for SMN1 mutations. Prenatal prediction was performed for 11 fetuses from 10 families with SMA. All of the samples to be tested were from the Department of Neurology, First Affiliated Hospital, Fujian Medical University, Fuzhou, China. MAIN OUTCOME MEASURES: All of the 87 patients and their parents were screened for SMN1 deletion by restriction fragment length polymorphism analysis and denaturing high-performance liquid chromatography (DHPLC). For those patients without the SMN1 deletion, the SMN1 copy numbers were detected by real-time fluorescence quantitative polymerase chain reaction and the subtle mutations of SMN were screened by direct sequencing. Prenatal prediction was performed by restriction fragment length polymorphism analysis, DHPLC, and linkage analysis for 11 fetuses. Furthermore, the SMN1 copy numbers and detected carriers of SMA were found by DHPLC and real-time fluorescence quantitative polymerase chain reaction in 14 parents and the fetuses without the SMN1 deletion. Results in aborted fetuses and born babies were reconfirmed by restriction fragment length polymorphism analysis and DHPLC. The born babies were followed up and physically examined twice a year. RESULTS: The frequency of the SMN1 deletion we detected was 93.5% (72 of 77 patients). No subtle mutations were detected in the other 5 families. Four fetuses had the SMN1 deletion and were aborted. The other 7 fetuses, 4 carriers and 3 normal individuals, were born under suggestion by the physician. Fourteen parents were carriers. The reconfirmation of results in the aborted fetuses and born babies was completely consistent with prenatal prediction. The 7 born babies were followed up until recently and all were normal. CONCLUSIONS: The molecular diagnosis system based on restriction fragment length polymorphism analysis, DHPLC, and linkage analysis is an efficient and accurate method that is well suited for routine use in clinical laboratories.     

Pathophysiology and postnatal outcome of fetal hydrocephalus

At the National Kagawa Children's or Kobe University Hospital, 24 cases of fetal hydrocephalus were managed between 1982 and 1988. There were 8 simple, 11 dysgenetic, and 5 secondary cases of hydrocephalus, and the fetal age at diagnosis ranged between 24 and 40 weeks of gestation (average 33.4 weeks). All were diagnosed using ultrasonography, with either magnetic resonance imaging or whole-body computed tomography, additionally performed in 10 patients to determine their usefulness in evaluating the morphology. Four patients underwent transabdominal or transvaginal cephalocentesis in the prenatal period and intracranial pressure was measured during the drainage of cerebrospinal fluid in two of these. Postnatal outcome was analyzed for each type of hydrocephalus. The results suggested that in such cases the fetal brain is subjected to extremely high intracranial pressures resulting from a mixture of hydrocephalic pressure and intermittent uterine constriction. Immediately after birth, the biparietal diameter was found to be increased by an average of 7.7 mm and the hydrocephalic state was transformed into the neonatal type characterized by macrocephaly and a relatively low intracranial pressure. Overall mortality was 25% and 16 of the 24 infants underwent the postnatal shunt procedure, largely at the neonatal stage. The follow-up period varied from 4 months to 6 years (average, 25.8 months for nonfatal cases) and the mean intelligence or developmental quotient was 45.2. There were no significant differences in postnatal outcome between the three major types of fetal hydrocephalus. Findings revealed that the length of the gestation period after the diagnosis of hydrocephalus has a significant effect on outcome (P<0.01). Based on these results, it is suggested that fetal hydrocephalus may be extremely hypertensive and that impairment of neuronal functional development accompanying its prenatal progression can be irreversible.     

胎儿MRI对椎管内脂肪瘤产前诊断及预后评估的价值

目的 探讨胎儿MRI对椎管内脂肪瘤产前诊断及其治疗方案选择的价值.方法 回顾分析18例胎儿期诊断为椎管内脂肪瘤患儿的临床资料.分析比较产前超声和胎儿MRI与出生后MRI的诊断符合率;统计分析患儿的症状、体征及脂肪瘤类型,总结胎儿期发现椎管内脂肪瘤及其处理的经验.结果 本组18例患儿中,以出生后MRI为标准,产前超声正确...     

Descriptive epidemiology of spinal muscular atrophy type I in Estonia

Spinal muscular atrophy is the second most frequent autosomal-recessive disorder in Europeans. There are no published epidemiological data on SMA in Estonia and other Baltic countries. The aim of this study was to estimate the incidence of SMA I in Estonia. All patients with SMA I diagnosed between January 1994 and December 2003 were included in the study. The diagnosis was established on the basis of neurological evaluation, ENMG findings, molecular studies and muscle biopsy. PCR and restriction enzyme analysis was used to detect the homozygous deletion of the SMN1 gene. A total of 9 cases of SMA I were identified during this 10-year period. The incidence of SMA I in Estonia is 1 in 14,400 live births, which is similar to the result from Hungary but lower than average incidence in the world. Only one of the patients was female. Typical SMN1 gene deletion was found in all cases.     

Epidemiology of spastic tetraplegic cerebral palsy in Sweden. II. Prevalence, birth data and origin

The prevalence and origin of spastic tetraplegic cerebral palsy (TPL) was investigated in a population-based study from 15 Swedish counties and the city of Gothenburg. The series comprised 96 children and adolescents born in 1959-1978. The prevalence at the ages of 5-24 years was 8 per 100,000. The etiological analysis was based on the 91 TPL subjects, born in Sweden. The preterm rate was 7%. There were 46 males and 45 females. Excluding postnatal cases, the mean birth weight was 2949 g and the proportion of SGA 21%. An obvious prenatal origin was found in 21 (mainly microcephaly, other CNS maldevelopment, intrauterine CMV-infection), an obvious perinatal origin in nine (mainly cerebral hemorrhage), and an obvious postnatal origin in 16 (mainly CNS infection). A potential prenatal origin was considered in six, a combined pre- and perinatal in 15, a perinatal in 13 and in 11 the origin of TPL was untraceable. An optimality analysis showed that reduced optimality in the partum and postpartum periods discriminated between pre- and perinatal etiology of TPL. Cases with obvious perinatally derived TPL had a high load of complications in the partum and postpartum periods, whereas these periods had been fairly uncomplicated in cases with an obviously prenatal origin of TPL. - It was indicated that some 50-55% of TPL was prenatally, around 30% perinatally and some 15-20% postnatally derived. The low preterm rate as well as the proportion of perinatal brain damage in TPL cases has probably increased in recent birth year periods due to the appearance of very preterm, severely multi-impaired children in the CP panorama.     

A predominantly cervical form of spinal muscular atrophy.

Clinical heterogeneity within the group of spinal muscular atrophies (SMA) in children can pose practical problems of diagnosis, prognosis and genetic counselling. In addition to the classic forms, unusual cases have been described. Five children with an atypical type of SMA are reported, characterised by early involvement of cervical muscles contrasting with initially mild or absent affection of peripheral muscles. Secondary involvement of respiratory muscles was responsible for the death of three children in the second to fourth year. The disorder may be recessively inherited.     

Advances in SMA research: Review of gene deletions

The term spinal muscular atrophy (SMA) is used to encompass a group of inherited disorders in which the striking pathological feature is loss of the cell bodies of alpha motor neurons in the anterior horn cell of the spinal cord and, in some cases, of the bulbar motor nuclei. Although the pathological features of these disorders have been well characterized, the nature of the primary underlying biochemical abnormality remains to be determined. In the 1990s genetic linkage was established for the childhood onset recessive forms of SMA (types I, II and III) to markers mapping to the chromosomal region 5q11.2–13.3. Physical maps of the region were then constructed, several candidate genes isolated and in 1995 deletions in two genes, the survival motor neuron (SMN) gene and the neuronal apoptosis inhibitory protein (NAIP) gene, were identified in significant numbers of patients. Already the impact of the characterization of these deletions is being seen in clinical practice in terms of aiding diagnosis in symptomatic cases and in prenatal diagnosis. As discussed in this review however, several questions remain unresolved. It is unclear whether deletions in one or both of these genes, or indeed in other, as yet unidentified, genes are important in generating the SMA phenotype. The function of the protein product of the SMN gene is unknown. The NAIP gene encodes a protein which inhibits apoptosis in a mammalian cell line: is it disruption of this function which is relevant in SMA? What underlies the variation in disease severity evident both between and within families? Resolution of such issues is of crucial importance if the identification of these deleted gene sequences is to lead to the development of rational therapies for motor neuron diseases.