目的：分析近亲家系全外显子测序（whole exome sequencing, WES）中漏诊5例进行性肌阵挛共济失调（progressive myoclonic ataxia, PMA）患者的原因,并探讨对策。方法：收集5例WES未发现致病突变而临床拟诊为PMA患者,对其近亲婚配家系（三代以内旁系血亲婚配）进行全基因组SNP芯片扫描,通过纯合子定位技术及单倍型分析定位致病区间,结合患者的肌阵挛和共济失调表型,明确其可能的致病基因。采用Sanger测序对候选的突变位点进行家系共分离分析,最后通过溯源WES比对过程中的SAM与BAM文件,分析WES漏诊的原因。结果：纯合区间定位和重分析WES发现,5例PMA家系为NEU1基因c. 544A>G（p.S182G）纯合突变导致的Ⅰ型唾液酸沉积症（sialidosis type Ⅰ, ST-Ⅰ）。人类基因组参考序列中的ALT contig在WES比对过程中可造成包括NEU1基因在内的多个PMA致病基因检出遗漏。结论：临床诊断中,常染色体隐性遗传的PMA需关注NEU1基因突变所导致的ST-Ⅰ。对于WES未发现致病位点的PMA家系,可结合家系遗传方式、全基因组SNP芯片等方法定位致病区间,再结合患者的临床表型以明确其疾病致病基因。

Objective: To investigate the causes and strategies of missed diagnosis of progressive myoclonic ataxia (PMA) consanguineous families by whole exome sequencing (WES). Methods: Five PMA consanguineous families with no disease causative variants detected by WES were enrolled, and homozygosity mapping and haplotype analysis for locating disease related region were performed. Further combined with myoclonus and ataxia phenotypes, the possible pathogenic genes were identified. Sanger sequencing was used to verify the candidate mutation and perfomed family co-segregation in five families. Finally, the reasons for missed diagnosis were analyzed by tracing to the SAM and BAM files from WES alignment process. Results: By homozygous regional mapping and reanalysis of WES, 5 families with progressive myoclonic ataxia were identified as sialidosis type I (ST-I) caused by homozygous mutation of NEU1 gene c.544A >G(p.S182G). It was also found that ALT contig in human genome reference sequence could cause multiple pathogenic genes including NEU1 gene to be missed during WES alignment. Conclusions: In clinical diagnosis, autosomal recessive PMA should be paid attention to ST-I which caused by NEU1 gene mutation. For families with hereditary diseases in which WES has not found pathogenic loci, the pathogenic region can be located by combining family genetic mode and genome-wide SNP chip, then the pathogenic genes can be identified by clinical manifestations analysis.