儿童脊肌萎缩症运动神经元生存基因缺失分析

Deletions of SMNt Gene in the Children with Spinal Muscular Atrophy

目的评价聚合酶链反应-限制性片段长度多肽性(PCR-RFLP)分析技术在脊肌萎缩症(SMA)临床诊断中的价值,分析端粒侧运动神经元生存基因(SMNt)表达与SMA临床分型之间的关系。方法对临床拟诊为SMA的23例患儿同时采用临床诊断标准和PCR-RFLP分析技术进行诊断,两种结果对比,分析灵敏度、特异度、Kappa值及P值。结果(1)临床诊断与PCR-RFLP基因诊断结果比较:23例拟诊患儿中临床确诊为SMA者18例,非SMA者5例。PCR-RFLP技术检测结果:5例非SMA者,SMNt基因检测均无缺失;18例确诊SMA者,SMNt基因缺失者15例,无SMNt基因缺失者3例,缺失频率为83.3%。此方法的灵敏度为83.3%,特异度为100%,阳性预测值100%,阴性预测值62.5%,真实性为86.96%,Kappa值为0.685。(2)SMA不同临床分型中SMNt基因7、8号外显子缺失检测结果:I型患者以7、8号外显子缺失为主,SMNt基因缺失频率100.0%;Ⅲ型患者以7号外显子缺失为主,SMNt基因缺失频率为66.7%;I型患者7、8号外显子联合缺失频率较Ⅲ型高(P<0.05)。结论(1)PCR-RFLP分析技术简便、快捷、特异性高,敏感性好,适用于临床儿童型SMA的基因诊断,尤其对于SMAI型患者。(2)SMNt基因7、8号外显子联合缺失常常提示病情严重,预后不良;单独缺失提示病情较轻,预后较好。

Objective To assess the diagnostic value of Polymerase chain reaction-restriction fragment length polymorphism（PCR-RFLP） in children with spinal muscular atrophy and analyze the relation between telomeric portion of survival motor neuron gene expression and the types of SMA in terms of clinical. Methods Twenty-three children with suspicion of spinal muscular atrophy in terms of clinical features were simultaneously diagnosed by gold standard and PCR-RFLP. The results from two methods were compared by the sensitivity, specificity, Kappa and probability. Results （1）Of totally 23 cases enrolled in this study,the 18 SMA and 5 non-SMA were diagnosed by the gold standard. However, the SMNt no deletion in 5 cases of non-SMA; the SMNt homologous deletion of 15 cases and no deletion of 3 cases in 18 cases of SMA was detected by PCR-RFLP. The total deletion rate of SMNt gene was 83.3%. Compared with the gold standard, the sensitivity of PCR-RFLP was 83.3% and specificity was＇100%. The positive predictive value was 100% ,negative predictive value was 62.5% ,validity was 86.96% ,and the Kappa value was 0. 685. （2）The detection of SMNt gene deletion showed that the SMNt deletion of both exon 7 and 8 accounted for 100.0% in type Ⅰ SMA,and 0 in type Ⅲ SMA. On the contrary,the SMNt deletion rate of only exon 7 was 66.7%,and the deletion rate of both exon 7 and 8 in type Ⅰ SMA was higher than type Ⅲ SMA（P〈0.05）. Conclusion （1）PCR-RFLP was a simple,rapid and time-saving diagnostic method for SMA,and it was sensitive and specific,which was worth popularizing,especially for SMA Ⅰ. （2）The deletion of both exon 7 and 8 often means serious symptom and poor prognosis,whereas only exon 7 or 8 deletion often predicts light symptom and relatively good prognosis.