MERRF syndrome (or Myoclonic Epilepsy with Ragged Red Fibers) is a mitochondrial disease. It is extremely rare, with an estimated prevalence of 1/400,000 in Northern Europe, and has varying degrees of expressivity owing to heteroplasmy.

MERRF syndrome (or Myoclonic Epilepsy with Ragged Red Fibers) is a mitochondrial disease. It is extremely rare, with an estimated prevalence of 1/400,000 in Northern Europe, and has varying degrees of expressivity owing to heteroplasmy.