Myoclonic epilepsy, ragged red fibres (Q95631)

Myoclonic epilepsy associated with ragged red fibres (MERRF) is a rare mitochondrial disorder. Typical manifestations of the disease are myoclonus, generalised epilepsy, cerebellar ataxia and ragged red fibres on muscle biopsy. Point mutations in the tRNA Lys gene of the mitochondrial DNA, mainly A8344G, are responsible for almost 90% of MERRF cases. Morphological changes seen upon muscle biopsy include a substantive proportion of ragged red fibres, muscle fibres showing a deficient activity of Cytochrome c oxidase and the presence of vessels with a strong reaction for succinate dehydrogenase and Cytochrome c oxidase deficiency.