该文报道血浆瓜氨酸（plasma citrulline, pCit）浓度降低对于MT⁃ATP6基因相关线粒体病早期识别的价值。病例1，3月龄急性起病，迅速进展为代谢危象、多器官功能衰竭及中枢性呼吸衰竭而夭折。病例2，6月龄发病，逐步出现发育落后，影像学显示双侧基底节对称性病变，诊断为Leigh综合征，在补充瓜氨酸及综合干预后，智能发育和代谢指标均得到改善。2例患儿均存在MT⁃ATP6基因m.8993T>G（p.L156R）变异，确诊为MT⁃ATP6基因相关线粒体病。该病例系列提示，新生儿疾病筛查pCit浓度降低应警惕线粒体MT⁃ATP6基因相关线粒体病可能，早期诊断和代谢干预有利于改善预后。

This report describes the potential diagnostic value of decreased plasma citrulline (pCit) levels for the early recognition of MT-ATP6-related mitochondrial disease. Two cases were reported, and relevant literature was reviewed. Case 1: Onset occurred at 3 months of age with an acute presentation that rapidly progressed to metabolic crisis, multiorgan failure, and central respiratory failure, resulting in death in early infancy. Case 2: Onset occurred at 6 months of age with progressive developmental delay. Brain magnetic resonance imaging revealed bilateral symmetric basal ganglia lesions, and Leigh syndrome was diagnosed. Following citrulline supplementation and comprehensive intervention, improvements were observed in intellectual development and metabolic indices. Both patients carried the MT-ATP6 variant m.8993T>G (p.L156R), confirming MT-ATP6-associated mitochondrial disease. This case series indicates that decreased pCit on newborn screening is an early biochemical marker of MT-ATP6-associated mitochondrial disease. Early diagnosis and metabolic intervention are beneficial for prognosis.