ObjectiveTo investigate the clinical characteristics and genetic phenotype of mitochondrial myopathy associated with lactic acidemia and stroke-like seizure syndrome (MELAS) in DNA A3243G mutation, and to improve the clinical understanding and diagnosis.MethodsThe clinical data and imaging characteristics of 4 patients with DNA A3243G mutation-related MELAS syndrome who were diagnosed and treated in the Department of Pediatric Neurology, Henan Provincial People's Hospital from June 2017 to June 2018 were retrospectively reviewed.ResultsOf the 4 patients, 3 were caused by convulsions, 1 was caused by dizziness, and the MELAS syndrome caused by mitochondrial DNA A3243G mutation was confirmed by genetic testing. The patients were treated with anti-epilepsy drugs. The patients were followed up for at least 1 year, and 2 of 4 patients were stable, 1 patient still had seizures, and 1 patient did not improved.ConclusionsThe clinical phenotypic heterogeneity of patients with DNA A3243G mutation-related MELAS syndrome is caused by the " heterogeneity” and " threshold effect” of DNA mutation. The mutation rate of DNA A3243G is as high as 80%. In the era of promoting precision medicine, genes examination can help early diagnosis and early treatment of MELAS syndrome as well as improve the quality of life of patients and improve the prognosis.