The clinical characteristics and gene variations of a family with mitochondrial myopathy and ataxia caused by MSTO1 gene mutation who visited Xiangya Hospital of Central South University in October 2019 were retrospectively analyzed.The proband was an 11-year-old female, who was found to have delayed motor and language development and dysarthria at the age of 1 year and 6 months.The 9-year-old younger brother of the proband had similar symptoms at the age of 1 year and 3 months.Both the proband and her younger brother had muscle weakness and ataxia.Their head magnetic resonance imaging showed cerebellar atrophy, and their electromyography showed neuroge-nic changes.Genetic testing revealed compound heterozygous mutations in MSTO1: c.1259delG; p.G420VfsX2 and c.571 C > T; p.R191X, which were inherited from their parents, respectively.The same site mutations were found in the younger brother.After 2 weeks of " cocktail therapy" , the symptoms of the children were alleviated, and their language and movement improved.