Mitochondrial encephalomyopathy with lactic acidosis and strokelike episodes (MELAS): a mitochondrial disorder presents as fibromyalgia.

This case report describes a patient who presented with symptoms and signs of longstanding fibromyalgia. Routine laboratory tests revealed an elevated anion gap. Evaluation of the elevated anion gap demonstrated elevated lactate and pyruvate levels and a lactate-to-pyruvate ratio greater than 20:1.