Myoclonic epilepsy with red ragged fibers (MERRF)

Myoclonic epilepsy with red ragged fibers (MERRF) is a rare, multisystem mitochondrial disorder.

Clinical presentation

Patients usually present in late adolescence or early adulthood with


The diagnosis of MERRF is based on clinical symptoms (myoclonus, epilepsy, ataxia) and ragged-red fibers on muscle biopsy .


The mitochondrial gene MT-TK, which encodes tRNA, is the most commonly affected with an A-to-G transition at nucleotide 8344 (80%) .

  • serum and CSF lactic acidosis
  • high CSF protein

Radiographic features

Neuroradiological features of MERRF can be seen on CT and/or MRI :

Differential diagnosis

On imaging consider:

  • MELAS: differentiated by the presence of strokes in MELAS