目的 通过同一家系中两个相同 MOCS1 基因变异序列、却不同临床表型特点的分析，希望未来对这种相关性研究提供可靠临床资料。方法 应用高通量测序技术对先证者家系行致病基因检测， 回顾分析 2 例 A 型钼辅因子缺乏症（MoCD）患者的临床特点和基因变异序列。结果 先证者为足月儿， 无窒息史，生后喂养困难，第 2 天出现抽搐，MRI 示双侧基底节缺氧缺血性损伤和软化灶；3 个月随访神经发育评估轻度落后。其 5 岁姐姐生后精神运动发育描述正常，10 月时因“高热”突然出现抽搐，随即出现进行性全面神经发育倒退；MRI 同样提示基底节缺氧缺血性改变。故行家系 5 人全外显子高通量测序，先证者和患病姐姐检出 MOCS1 基因 NM_001358530.2，c.1275delA（p.Gly426Aspfs Ter10）纯合变异，其父母和 另一个健康胞姐均为杂合变异。该变异位点未被报道。结论 先证者和其患病胞姐具有相同 MOCS1 基 因的突变序列，但二者临床过程并不相同。推测可能先证者亚硫酸盐氧化酶活性尚有残余功能，故临床表型温和。 

Objective To analyze two identical novel MOCS1 gene variant sequences in the same family⁃ with different clinical features，and to provide reliable clinical data for future research on this correlation study. Method The pathogenic gene of the proband′ s family was detected by high ⁃throughput sequencing technology， and clinical features and gene variation sequences of the two patients with type A molybdenum cofactor deficiency from the same familywere retrospectively analyzed. Result The proband was a full⁃term infant with no history of asphyxia，who had difficulty feeding after birth，and had convulsions on the second day. Head MRI showed bilateral basal ganglia hypoxic⁃ischemic damage and softening lesions. His 5⁃year⁃old sibling sister had no abnormal psycho⁃ motor development after birth，but at 10 months，sudden fever and convulsions，feeding difficulties，and progres⁃ sive overall neurodevelopmental regression were observed. Head MRI also showed hypoxic ⁃ischemic in the basal ganglia. Therefore，the whole exon high⁃throughput sequencing of 5 members of the family were performed. The pro⁃ band and his affected sister were NM of MOCS1 gene_ 001358530.2，c.1275delA（p.Gly426Aspfs Ter10）homozy⁃ gous variant，but the parents and another healthy sister all heterozygous variants. This variant site had not been reported. Conclusion The proband and his affected sister have the same MOCS1 gene mutation sequence but dif⁃ ferent clinical processes.It is speculated that the mild phenotype of the proband may result in the residual function of sulfite oxidase activity