目的 探讨联合氧化磷酸化缺陷 21 型（COXPD21）的临床及分子遗传学特征。方法 回顾分析 1 例 COXPD21患儿的临床资料，结合文献进行复习。结果 6月龄男性患儿，发育落后，3月龄起出现癫痫，表现为局灶性发作、 痉挛、肌阵挛，呼吸道感染后抽搐加重，并出现昏迷、发绀、呼吸急促、心音低钝、肝大、四肢肌张力增高。实验室检查示心 肌弥漫性损害、严重酸中毒、高乳酸血症。全基因组测序显示患儿存在TARS2基因复合杂合变异，c. 987 _ 988 insA及c. 470 C>G，均为新发变异。患儿确诊为COXPD21，于7月龄死亡。结论 COXPD21起病早，预后差，可导致严重的代谢性脑病， 由TARS2基因变异引起，该变异国内未见报道。

Objective To explore the clinical features and molecular genetic characteristics of combined oxidative phosphorylation deficiency- 21 (COXPD 21 ). Method The clinical data of COXPD 21 in a child were retrospectively analyzed and the related literature was reviewed. Results A 6 -month-old boy had developmental retardation. Epilepsy began at 3 months of age and was manifested with focal seizures, spasms, and myoclonus. The convulsions aggravated after respiratory infections, accompanied by comma, cyanosis, breathlessness, low cardiac sound, hepatomegaly, muscular hypertonia of extremities. The laboratory examinations showed diffuse myocardial damage, severe acidosis and hyperlactic acidemia. Whole genome sequencing (WGS) revealed that the proband had compound heterozygous variations in the TARS 2 gene, c. 987 _ 988 insA and c. 470 C>G, both of which were new variations. The child was diagnosed with COXPD 21 and died at the age of 7 months. Conclusions COXPD 21 has an early onset and poor prognosis, and can lead to severe metabolic encephalopathy. It is caused by TARS2 gene variation. This is the first reported case of COXPD 21 confirmed by genetic testing in China.