Abstract We present a case report of a 25 year-old man with MELAS (Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes) syndrome, who died suddenly and unexpectedly from diabetic ketoacidosis. This case report illustrates why it is important for medical examiners to be familiar with the clinical and autopsy features of MELAS syndrome and to be aware of the common complications, which may lead to sudden unexpected death.