We report a case of MELAS/Leigh superimposed syndrome with cervical myelopathy that rapidly progresses and deteriorates, describing its clinicopathologic features, the evolution of the disease, and the characteristics of the gene mutation. METHODS: The patient was a female, 13 years old, who developed numbness and tautness of both lower limbs after mountain climbing in March 2012, with frequent convulsions of the left lower limb, accompanied by 1 episode of loss of consciousness, and unsteady walking, and the MRI in the local hospital suggested that the right cerebral peduncle and frontal cortex had abnormal signals, and the cervical medulla stripe from C2-C6 had abnormal signals; the cerebrospinal fluid was normal. “She was discharged from the hospital with methylprednisolone shock and gammaglobulin treatment, and was discharged in December 2012 with sudden onset of nausea and vomiting, twitching of limbs with urinary incontinence, and numbness and weakness of the right limbs, and MR showed that there were new foci in the left cerebellar hemisphere, bilateral thalamus, and bilateral frontal cortex, and that foci of the cerebral peduncle and the right frontal cortex had been enlarged. He was discharged from the local hospital as “multiple sclerosis” with methylprednisolone shock therapy, and on February 22, 2013, he developed weakness of the right side of the limbs, and convulsions of the right side of the limbs and face. Cerebrospinal fluid biochemistry, routine, IgG index was normal, cerebrospinal fluid oligoclonal bands, aquaporin 4 were negative. 3-17, due to left side of the mouth twitching, MRI showed bilateral parietal lobe new foci. 4-13, due to twitching with unconsciousness, shortness of breath came to the emergency room of our hospital, blood gas analysis Ph 6.848, PO2 65.5, blood lactate 18 mmol/L, was given trachea tube intubation, correcting the acid, etc., and then extubated on the next day, MRI showed bilateral parietal lobes. On April 24, she developed myoclonus, excitability, irritability, binocular diplopia, ataxia, binocular horizontal nystagmus, MRI showed new lesions in the brainstem and cerebellum, and she was discharged from the hospital with partial improvement. 7-28, she developed headache and nausea, blood pressure of 80/45mmHg, ocular dyskinesia, which progressed to respiratory distress, lethargy, unresponsiveness, and GCS score of 7, MRI suggested bilateral midbrain and cerebellum. 7 points, MRI suggested bilateral cerebellum, cerebral bridge, medulla oblongata, midbrain new foci. on August 11, sudden respiratory weakness, blood pressure decreased, confusion, oxygen saturation 60%, was intubated, ventilator-assisted respiration. on August 20, transferred to the local hospital in a shallow coma, spontaneous respiration existed, occasional spontaneous agitation of the limbs, bilateral baroreflex sign was positive. on September 22, off the machine when he went home, the patient was clear consciousness, could not speak, could open the eyes, and the right side of his head was in the right side of the brain, and he was in the left side of the brain, and was in the right side of the brain. He was able to open his eyes, and there was retraction of the right limb with pain stimulation.He died in the local hospital on 2013-10-26 after having convulsions and coma again. Results: 2013-2-28 muscle biopsy, enzyme staining of broken red fibers, electron microscopy suggests that the number and morphology of mitochondria abnormal. Whole blood mtDNA sequencing suggested 13094T>C mutation, muscle DNA results 13094T>C nearly pure mutation, confirmed the diagnosis of mitochondrial disease. Maintenance therapy with mitochondrial protective drugs such as coenzyme Q10, leucovorin, and vitamin B2 was started. CONCLUSION: This is the first report of 13094T>G mutation causing MELAS/Leigh syndrome in China; the presence of cervical myelopathy is rare in mitochondrial disease; the course of the disease with frequent relapses, exacerbations and even death despite mitochondrial protective drug therapy is different from that of patients with 3243A>G mutation.