新生儿期发病的脊髓性肌萎缩及其基因诊断（附四例报告）

Spinal muscular atrophy happened in neonatal period and its gene diagnosis-4 case reports

目的总结新生儿期发病的脊髓性肌萎缩（spinal muscular atrophy，SMA）的临床特征，探讨基因诊断的方法和意义。方法分析4例新生儿期发病的SMA-Ⅰ型患儿的临床特点和神经电生理改变，应用聚合酶链反应-限制性片段长度多态性分析技术对其中1例患儿进行运动神经元生存基因（survival motor neuron，SMN）的检测。结果4例患儿临床均表现为肌无力、肌张力低下、特殊的蛙腿体位；神经电生理检测显示为神经源性损害，2例运动神经电位引不出；1例患儿进行了基因检测显示SMN基因第7、8外显子纯合缺失。结论定性检测SMN基因第7、8外显子缺失是SMA-Ⅰ型可靠的基因诊断方法。聚合酶链反应-限制性片段长度多态性分析结果可靠，方法简单、快速，易于临床普及。基因诊断结合传统诊断标准不仅可大大提高SMA-Ⅰ型诊断准确率，还可为产前诊断提供依据，减少患儿出生。

Objective To summarize the clinical features of spinal muscular atrophy （SMA） developed in neonatal period, and to investigate the method and significance of diagnosis of SMA by gene deletion analysis. Method The clinical characteristics and neuro-electrophysiological change were assessed in all 4 neonates with SMA. Exon 7 and 8 in survival motor neuron （SMN） gene was analyzed by polymerase chain reaction-restriction fragment length polymorphism（PCR-RFLP） in one patient and their parents. Result Myasthenia, hypotonia, special frog leg position were the most common clinical manifestations of SMA-I in neonatal period. Neuro-electrophysiological study showed a pattern of neurogenic injury in all 4 patients, and no motor potential in 2 patients. Deletion of exon 7 and 8 in SMN gene was found in one patient. Conclusion PCR-RFLP is a reliable gene diagnosis method to detect the deletion of exon 7 and 8 of SMN gene for SMA-I patient. The method of PCR- RFLP can not only provide a reliable result, but also provide a simple and rapid way to make a diagnosis. Combined with the traditional diagnostic criteria, gene diagnosis can improve the diagnosis accuracy of SMA-I, which can also help the prenatal diagnosis to decrease the birth rate of SMA-I patients.