摘要目的:总结晚发型线粒体脑肌病伴乳酸酸中毒和卒中样发作(MELAS)患者的临床、影像学、肌肉病理和基因突变特点。方法:新乡医学院附属焦作市人民医院神内科自1997年1月至2021年12月收治3例晚发型MELAS患者，均采用基因二代测序技术对患者进行线粒体DNA(mtDNA)和核DNA(nDNA)突变筛查。回顾性分析患者的临床、影像学、肌肉病理和基因突变特点。结果:3例患者的临床表现主要包括卒中样发作、头痛、听力下降、偏盲、认知功能减退和精神异常等。3例患者双上肢肌张力、肌力均正常。2例患者双下肢肌张力增高、腱反射活跃、病理征阳性。MRI检查显示3例患者颞枕顶叶皮质及皮质下长T1、长T2异常信号，CT扫描显示1例患者双侧苍白球钙化。肌肉病理染色显示3例患者有破碎红纤维(RRF)和破碎蓝纤维(RBF)，2例患者有细胞色素C氧化酶(COX)阴性肌纤维。基因检测结果显示3例患者 MT-TL1基因m.3243A>G点突变，其中2例患者血液中突变比例分别为15%、17%，1例患者肌肉组织中突变比例为73%。 结论:晚发型MELAS患者肌肉病理染色可发现较高比例的RRF。m.3243A>G点突变是晚发型MELAS最常见的突变类型，其在肌肉组织中的突变比例明显高于血液。

abstractsObjective:To summarize the clinical, imaging, muscle pathological and gene mutational features of patients with late-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS).Methods:Three patients with late-onset MELAS, admitted to Department of Neurology, Jiaozuo People's Hospital Affiliated of Xinxiang Medical University from January 1997 to December 2021 were chosen; all patients were screened for mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) mutations by second-generation gene sequencing. The clinical, imaging, muscle pathological and gene mutational features of patients with late-onset MELAS were analyzed retrospectively.Results:The main clinical manifestations of these late-onset MELAS patients included stroke-like attacks, headache, hearing and vision loss, cognitive decline and mental disorder. The muscle tension and muscle strength of both upper extremities in these 3 patients were normal. Increased muscle tension and active tendon reflexes, and positive pathological signs in both lower extremities were noted in 2 patients. Head MRI showed abnormal long T1 and long T2 signals in temporal occipital parietal cortex and subcortex in 3 patients, and CT showed calcification in bilateral globus pallidus in 1 patient. Ragged red fibers (RRF) and ragged blue fibers (RBF) were found in the muscle biopsies of 3 patients, and cytochrome oxidase (COX)-negative muscle fibers were found in 2 patients. MT-TL1 gene m.3243A>G mutation was detected in all 3 patients by genetic testing, among which mutation in the blood of 2 patients was 15% and 17%, respectively, and mutation in the muscle tissues of 1 patient was 73%. Conclusion:Muscle pathology indicates high RRF percentage in patients with late-onset MELAS; and m.3243A>G spot mutation is the most common mutation type in late-onset MELAS, and m.3243A>G mutation ratio in muscle tissues is obviously higher than that in blood.