MELAS syndrome and MIDD unmasked by metformin use

A case report described a patient found to have mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome and maternally inherited diabetes and deafness (MIDD).


A patient was seen in the hospital for new-onset seizure disorder and found to have mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), a syndrome caused by genetic defects in mitochondrial DNA, according to a recent case report.

The report, published as a letter by Annals of Internal Medicine on Aug. 25, describes how the patient had been recently diagnosed with diabetes and had started taking metformin. He also had bilateral sensorineural hearing loss diagnosed at age 15 years, which was determined to be part of maternally inherited diabetes and deafness (MIDD).

“To our knowledge, this is the first report of a patient whose MELAS syndrome and MIDD were recognized after the patient began use of metformin. We hope our report of this patient's experience will help clinicians understand why they should exercise caution in prescribing metformin to patients with features of mitochondrial disease,” the authors wrote.