MELAS (mitochondrial cytopathy, encephalomyopathy, lactic acidosis and stroke-like episodes) is a syndrome in which signs and symptoms of gastrointestinal disease are uncommon if not rare. We describe the case of a young woman who presented as an acute surgical emergency, diagnosed as toxic megacolon necessitating an emergency total colectomy. MELAS syndrome was suspected postoperatively owing to persistent lactic acidosis and neurological symptoms. The diagnosis was later confirmed with histological and genetic studies. This case highlights the difficulties in diagnosing MELAS because of its unpredictable presentation and clinical course. We therefore recommend a high index of suspicion in cases of an acute surgical abdomen with additional neurological features or raised lactate.