Objective To analyze the clinical and imaging characteristics of a patient with maternally inherited diabetes and deafness syndrome (MIDD) complicated with cerebral artery occlusion and explore the trend of mitochondrial gene mutations in her pedigree. Methods The study reviewed a patient with diabetes, deafness, dizziness and stroke like attack, who was diagnosed as mitochondrial encephalomyopathy with lactic acidosis and stroke-like episode (MELAS) syndrome and the medical history of her family members. Based on medical history, laboratory examinations, imaging examinations, genetic tests, and existing literature reports, the relationship between clinical characteristics of the patients in this family and pathogenic gene heterogeneity was analyzed. Results The proband presented typical clinical manifestations of MIDD, and the results of first-generation mitochondrial gene sequencing showed a chrM: 3243A>G (tRNA Leu1) mutation. Subsequently, next generation sequencing was performed using the blood of the proband and their maternal relatives, and the results showed that the blood mutation rate of proband was 42.15%, and most of the maternal relatives also exhibited different degrees of 3243A>G mutations. Conclusions The clinical manifestations of MIDD patients are complicated, and they are prone to brain atrophy and cerebrovascular occlusion. Sequencing analysis and early brain imaging evaluation is recommended to perform in diabetic patients with extreme emaciation and progressive hearing loss. Next-generation sequencing could help to clarify mutation heterogeneity. The higher heterogeneity and earlier onset age might indicate the more serious condition of the disease, which needs early prevention and diagnosis.