To the editor:A two-and-half-year-old girl was admitted to our hospital due to recurrent seizures.At 6 months old,she was found to have developmental retardation accompanied with polydipsia and polyuria.At 2 years and 2 months old,it developed to epileptic seizures with a frequency of 2 or 3 times a day.At the time of hospitalization,the neurological examination was normal.Routine urine test revealed a high pH value (8.0) with normal specific gravity.Blood biochemical examination displayed hypokalemia,hypouricemia,and hyperchloremia.Blood gas analysis indicated a low pH value,actual bicarbonate radical and base excess.Both blood amino acids and urinary organic acids were normal.Enzymatic activity detection of the mitochondrial respiratory chain in peripheral blood lymphocytes showed enzyme defects of complex Ⅰ and complex Ⅰ plus Ⅲ.Electroencephalography showed adventitious high-voltage sharp waves in the parietooccipital area.And no abnormal change was detected by brain magnetic resonance imaging.