小儿进行性脊髓性肌萎缩83例临床分析

目的总结小儿进行性脊髓性肌萎缩(SMA)各类型的临床表现、神经电生理及肌肉病理特点,提高对本病的认识水平并探讨基因诊断及产前诊断的临床意义。方法83例各型SMA患儿,男55例,女28例,年龄1d∽14岁,平均23．7个月,对本组病例进行临床特点、神经电生理、肌肉病理及基因分析。结果83例SMA临床分为3型,其中SMA-1型60例,SMA-2型19例,SMA-3型4例,3型SMA各有特点,但临床均表现为近端肌肉无力,肌张力低下。本病为单纯运动神经元受累,故患儿电生理表现均为神经源性损害而无感觉神经受累及明显的运动神经传导速度减慢;2例行肌活检显示大组萎缩肌纤维;13例行运动神经元生存基因(SMN)检测,11例外显子7和8联合缺失,1例仅第7外显子缺失,1例仅第8外显子缺失。结论根据临床特点,电生理,肌肉病理及基因诊断可与其他松软婴综合征鉴别,而能确诊SMA。基因诊断可为产前诊断提供依据,达到预防本病发生的目的。

Clinical study of 83 cases with spinal muscular atrophy in children

OBJECTIVE: Spinal muscular atrophy (SMA) is a common autosomal recessive disorder and represents one of the most common genetic causes of death in childhood. The last 10 years have seen major advances in the field of SMA, but no curative treatment is available so far. This study aimed to analyze the clinical characteristics of SMA, improve the clinical diagnosis of SMA, and explore the importance of gene diagnosis and prenatal diagnosis of SMA by gene deletion analysis. METHODS: Totally 83 cases with SMA including 55 males and 28 females were enrolled in this study. The age was between 1 day and 14 years (average 23.7 months). The clinical characteristics and changes of electromyography were assessed in all cases. The muscular biopsy was performed in 2 of 83 cases. The deletion of survival of motor neuron gene (SMN) was detected by PCR and restriction endonuclease spectrum analysis in 13 of 83 cases. RESULTS: The 83 cases were subdivided into three clinical groups based on age of onset of symptom, age at death and achievement of certain motor milestone, 60 cases with type I, 19 cases with type II and 4 cases with type III. They were all characterized by symmetric muscle weakness (more proximal than distal) associated with atrophy, absence or marked decrease of deep tendon reflexes. Electromyographic studies showed a pattern of denervation with neither sensory involvement nor marked decrease of motor nerve conduction velocities in all cases. Muscle biopsy provided evidence of skeletal muscle denervation with groups of atrophy in 2 cases. The SMN detection revealed deletion of exon 7 and exon 8 in 11 of 13 cases, only lacking exon 7 in 1 of 13 cases and lacking exon 8 in 1 of 13 cases. CONCLUSION: SMA is characterized by degeneration of lower motor neuron associated with muscle paralysis and atrophy. The definite diagnosis of SMA will rely on the typical clinical characteristics, changes of electromyogram and muscle biopsy and gene deletion analysis. Gene diagnosis of SMA can provide a basis for prenatal diagnosis which is of great importance in preventing SMA.