Objective: To analyse the genetic cause of a proband with mitochondrial disease caused by FASTKD2 gene variation and uniparental disomy. Methods: Detailed medical history of a child suspected "mitochondrial disease" were inquired in Peking University First Hospital on November 23, 2017. c.810_820dup homozygous variation in FASTKD2 gene was found by high-throughput sequencing, and her mother had heterozygous variation, but her father didn't have such variation, which didn't conform to the genetic law of variation. Further clinical examinations and molecular genetic tests were carried out. The venous blood of the child and her parents was drawn, and genomic DNA was extracted. Sanger sequencing, polymerase chain reaction (PCR) testing, short tandem repeat (STR) analysis, chromosome microarray analysis and loss of heterozygosity (LOH) genetic relationship analysis were performed on the proband and the parents to determine the variation. Results: The clinical manifestations, physical examination and laboratory examination of the child supported the diagnosis of mitochondrial disease. c.810_820dup(p.Ser274Phefs*8) homozygous variant in FASTKD2 gene was identified. Sanger sequencing indicated that the mother was a heterozygote of the variant, while the father had no such variation, which did not conform to the genetic law. PCR testing and Sanger sequencing review to eliminate sampling errors, PCR amplification and sequencing errors. Non-biological father was excluded by STR analysis. Three large segmental LOH of FASTKD2 gene were found by chromosome microarray analysis, then the LOH relative analysis verified the child was a mixed maternal uniparental disomy of chromosome 2. The child was diagnosed as mitochondrial disease caused by oxidative phosphorylation coupling defect of type 44. Conclusions: In this study, an autosomal recessive mitochondrial disease which does not conform to the genetic law was found, and it was confirmed that this mitochondrial disease family had both pathogenic variation and uniparental disomy phenomenon. It was diagnosed as mitochondrial disease caused by type 44 oxidative phosphorylation coupling defect.
目的： 对一先证者为FASTKD2基因变异和单亲二体所致线粒体病的家系进行遗传学分析。 方法： 对2017年11月23日就诊于北京大学第一医院的1例疑诊为“线粒体病”的患儿进行病史询问，高通量测序发现患儿FASTKD2基因c.810_820dup纯合变异，母亲为杂合子变异，父亲无该变异，不符合变异遗传规律，进一步对该患儿进行相关检查及分子遗传学检测。抽取患儿及父母静脉血，提取基因组DNA，对先证者及其父母行Sanger测序、PCR检测、短串联重复序列（STR）分析、染色体微阵列分析和杂合性丢失（LOH）亲缘分析确定患儿变异情况。 结果： 患儿临床表现、体格检查及实验室检查支持线粒体病的诊断；基因测序发现患儿携带FASTKD2基因c.810_820dup（p.Ser274Phefs*8）纯合变异；Sanger测序提示母亲为该变异杂合子，父亲无该变异，不符合遗传规律；PCR检测及Sanger测序复查排除取样错误、PCR扩增和测序错误；STR分析排除非生物学父亲；染色体微阵列分析发现FASTKD2基因存在3个大片段节段性LOH；LOH亲缘分析证实患儿为2号染色体为混合型母源性单亲二体，确诊为44型氧化磷酸化偶联缺陷所致的线粒体病。 结论： 本研究发现了一种不符合遗传规律的常染色体隐性遗传性线粒体病，明确了该线粒体病家系同时存在致病变异和单亲二体现象，确诊为44型氧化磷酸化偶联缺陷所致的线粒体病。.