染色体微阵列分析联合多重连接探针扩增技术在Becker肌营养不良/Duchenne肌营养不良产前诊断中的应用:13例分析

Chromosome microarray analysis combined with multiplex ligation-dependent probe amplification technology in prenatal diagnosis of Becker muscular dystrophy/Duchenne muscular dystrophy:analysis of 13 cases

目的探讨染色体微阵列分析(chromosome microarray analysis,CMA)联合多重连接探针扩增(multiplex ligation-dependent probe amplification,MLPA)技术在Becker肌营养不良(Becker muscular dystrophy,BMD)/Duchenne肌营养不良(Duchenne muscular dystrophy,DMD)产前诊断中的临床应用价值。方法回顾性选择2017年1月1日至2022年12月31日,无BMD/DMD家族史,因产前筛查高风险、胎儿超声软指标或结构异常等在石家庄市第四医院产前诊断中心行羊膜腔穿刺产前诊断,常规CMA提示胎儿Xp21.1区域(涉及DMD基因)拷贝数变异的孕妇13例(均为单胎妊娠),运用MLPA技术进行胎儿DMD基因的缺失/重复变异检测。经MLPA证实携带DMD基因外显子缺失/重复的胎儿,采用MLPA技术进行孕妇DMD基因缺失/重复变异验证,明确胎儿变异来源。总结CMA联合MLPA技术在无BMD/DMD家族史的BMD/DMD产前诊断中的应用价值。采用描述性统计分析。结果(1)11例CMA检出Xp21.1区域(涉及DMD基因)拷贝数缺失变异病例中,6例为新发变异,5例为母源性变异(含2例致病性变异);2例为致病性变异,9例为可能致病变异。经MLPA验证,2例DMD基因外显子半合子缺失(影响阅读框),考虑为致病性变异,孕妇选择终止妊娠;另外9例变异位点为杂合子缺失,均不影响阅读框,均选择继续妊娠至分娩。(2)2例CMA检出Xp21.1区域(涉及DMD基因)拷贝数重复变异,考虑为致病性变异且为母源,经MLPA证实为外显子半合子重复(影响阅读框),孕妇均选择终止妊娠。结论对于无BMD/DMD家族史及表型非特异但因其他指征需进行介入性产前诊断的胎儿,CMA联合MLPA有助于检出DMD基因外显子缺失/重复变异的胎儿,同时有利于孕妇DMD致病基因携带者的检出,可有效避免BMD/DMD患儿的出生。

Objective To investigate the role of chromosome microarray analysis(CMA)combined with multiplex ligation-dependent probe amplification(MLPA)in the prenatal diagnosis of Becker muscular dystrophy(BMD)/Duchenne muscular dystrophy(DMD).Methods This retrospective study enrolled 13 singleton pregnant women without a family history of BMD/DMD who underwent amniocentesis due to a high-risk result in prenatal screening,fetal ultrasound soft markers,or abnormal structural abnormalities at the Fourth Hospital of Shijiazhuang from January 1,2017,to December 31,2022.Routine CMA indicated fetal copy number variation in the Xp21.1 region(involving the DMD gene)in these subjects.MLPA was used to detect deletion/duplication mutations in the fetal DMD gene.For those with positive results,the mothers further underwent MLPA to identify the source of variations in the fetuses.The role of CMA combined with MLPA in the prenatal diagnosis of BMD/DMD in pregnant women without a family history of BMD/DMD was analyzed and summarized using descriptive statistical analysis.Results(1)Copy number deletion mutations in the Xp21.1 region(involving the DMD gene)were detected in 11 cases by CMA,including six with de novo variants and five with maternal variants(including two pathogenic variants);two with pathogenic variants and nine with likely pathogenic variants.MLPA showed that exon hemizygous deletion mutations(reading-frame was damaged)in the fetal DMD gene of two cases were pathogenic,and the pregnant women chose to terminate their pregnancies.The other nine mutations were found to be heterozygous deletions(reading-frame was not damaged),in the fetal DMD gene.(2)Two cases of copy number duplication mutations in the Xp21.1 region(involving the DMD gene)that were revealed by CMA were considered as maternally inherited pathogenic variants,which were confirmed by MLPA as fetal exon hemizygous duplications(reading-frame was damaged).Both pregnancies were terminated.Conclusion For cases without a family history of BMD/DMD or specific phenotypes that require invasive prenatal diagnosis,CMA combined with MLPA performs well in detecting exon deletion/duplication mutations in fetal DMD gene and in screening the carriers of pathogenic DMD gene in pregnant women,which could effectively avoid the birth of BMD/DMD-affected fetuses.