[Mitochondrial DNA deletion syndrome: a case report and literature review]

Summary Mitochondrial DNA（mtDNA） deletion is a rare occurrence that results in defects to oxidative phosphorylation. The common clinical presentations of mtDNA deletion vary but include mitochondrial myopathy, Pearson syndrome, Kearns-Sayre syndrome, and progressive external ophthalmoplegia. However, in clinical practice, some cases cannot be classified as any typical syndrome due to the absence or overlap of phenotypes. Here, we report one case of a 5-year-old girl who presented with progressive deterioration of her clinical status, which included systemic electrolyte disturbance, Fanconi syndrome and sensorineural hearing loss. Through a combination of systematic examinations and molecular analyses, mitochondrial disease was confirmed. A novel 6991-base pair deletion（deletion of mtDNA nt 7808-14798） was identified which confirmed molecular pathogeny of patient. Following treatment, the patient was stabilized and her hearing loss improved by hearing aid. This paper provided an important reference for the diagnosis and treatment of similar patients in clinical practice.