MERRF syndrome (MONDO_0010790) is a rare mitochondrial oxidative phosphorylation disorder characterized by myoclonic seizures, ataxia, generalized epilepsy, muscle weakness and ragged red fibers in the muscle biopsy. Also known as: Fukuhara syndrome, MERRF, myoclonic epilepsy - ragged red fibers, myoclonic epilepsy - ragged red fibres, myoclonus epilepsy and ragged red fibers, myoclonus epilepsy and ragged red fibres, myoclonus epilepsy associated with ragged-red fibers, myoclonus epilepsy associated with ragged-red fibres.