Objective:To analyze the clinical manifestations, blood biochemistry indexes, imaging and genetic characteristics of mitochondrial encephalomyopathy with lactic academia and stroke 1ike episodes (MELAS) in children, so as to provide the basis for the diagnosis of MELAS and reduce the misdiagnosis rate.Methods:The clinical data of children with MELAS admitted to the Second Affiliated Hospital of Wenzhou Medical University from January 2000 to December 2020 were retrospectively analyzed, and healthy children undergoing physical examination during the same period were selected as control group.The clinical data were compared between two groups, and the clinical manifestations, blood biochemistry indexes, electrocardiogram, cardiac ultrasound, cranial imaging and genetic testing were analyzed.Results:A total of eight children in MELAS group were collected, including three males and five females.The average age of onset was(9.90±3.89)years.There were eight children in control group, including four boys and four girls, with an average age of(7.92±2.51)years.Among the eight children with MELAS, there were six cases of vomiting, eight cases of epilepsy, five cases of headache, two cases of growth retardation, one case of mental retardation, one case of diabetes, and one case of peripheral neuropathy.The levels of lactate, lactate dehydrogenase, creatine kinase, and pyruvate in MELAS group were higher than those in control group, and the differences were statistically significant( P<0.05). Brain MRI abnormalities were observed in all patients, among which five patients had lesions located in the cerebral cortex, mostly in the parietal occipital temporal lobe, one patient had lesions located in the basal ganglia, and two patients had lesions in both cortex and basal ganglia.MRS of five cases showed inverted lactate peak with bimodal change.The electroencephalogram of eight cases showed slow wave of background activity, and epileptic discharge was observed in two cases.Seven children with MELAS had mtDNA locus mutation M. 3243A>G, and one patient had M. 8344A>G mutation.Eight cases were treated with symptomatic and supportive therapy, and were followed up for 3-5 years, most of them were hospitalized repeatedly because of similar chief complaints.The course of disease was prolonged and repeated, and the symptoms were relieved and discharged after about one week of hospitalization. Conclusion:The clinical manifestations of MELAS in children are diverse, and early diagnosis is difficult.Blood biochemistry, imaging characteristics and genetic testing results are helpful for early diagnosis, early treatment and delaying the progression of the disease.