Myoclonic epilepsy with red ragged fibers (MERRF)

Last revised by Dr Patrick J Rock on 06 Nov 2020

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

Patients usually present in late adolescence or early adulthood with 1-3

The diagnosis of MERRF is based on clinical symptoms (myoclonus, epilepsy, ataxia) and ragged-red fibers on muscle biopsy 3.

The mitochondrial gene MT-TK, which encodes tRNALys, is the most commonly affected with an A-to-G transition at nucleotide 8344 (80%) 3.

  • serum and CSF lactic acidosis
  • high CSF protein

Neuroradiological features of MERRF can be seen on CT and/or MRI 1,2:

On imaging consider:

  • MELAS: differentiated by the presence of strokes in MELAS

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