Mitochondrial diseases are a group of genetic metabolic disorders associated with abnormal mitochondrial oxidative phosphorylation function. Mitochondrial encephalomyopathies with hyperlactatemia and stroke-like episodes (MELAS) are the most common types. The clinical manifestations of typical MELAS include: (1) stroke like seizures in adolescence, most of which occur at the age of less than 40 years; stroke like seizures are characterized by sudden onset of weakness of one limb, mental symptoms, unresponsiveness, deafness, loss of vision, fever, headache and vomiting; (2) encephalopathy characterized by seizures and/or dementia; (3) muscle manifestations include post-exercise fatigue, post-exercise muscle pain, etc., but the clinical symptoms of myopathies are not prominent or are not recognized by the brain. clinical symptoms are mostly not prominent or masked by symptoms of encephalopathy; ④ skeletal muscle biopsy shows broken red fibers, vessels deeply stained with succinate dehydrogenase, and blood lactic acidosis. Its prominent stroke-like episodes most often affect the occipital lobe, resulting in sudden focal cerebral neurological deficits. Other manifestations include myoclonus, ataxia, episodic coma, optic nerve atrophy, retinitis pigmentosa, extraocular muscle paralysis, neurological deafness, cardiomyopathy, diabetes mellitus, gastrointestinal dyskinesia, renal disease, and short stature. The clinical presentation of mitochondrial gene A 3 2 4 3 G point mutation M E L A S differs somewhat in children and adults. The first symptoms in children are mostly migraine and hearing loss. The main symptom is epilepsy, followed by muscle weakness, hypertrichosis, headache with vomiting, dementia or mental retardation, and short stature, with less than one half of the children showing changes in vision and hearing. In adults, the first symptoms are headache and aphasia, followed by hearing loss, renal abnormalities, and epilepsy. The main symptom is dementia, followed by speech disorders and headache. About two-thirds of patients have other symptoms such as seizures and psychiatric symptoms, and one-half of patients have vision loss, hearing loss, and hemiparesis.