Myoclonic Epilepsy and Ragged-Red Fiber Disease (MERRF) is a mitochondrial encephalomyopathy characterized by myoclonic seizures, cerebellar ataxia, myopathy, and ragged-red fibers (RRFs) on muscle biopsy. RRFs are muscle fibers with subsarcolemmal mitochondria that stained red with Gomori trichrome stain. The MERRF syndrome is most commonly caused by the A8344G mutation in the mitochondrial tRNA Lys gene.
