myoclonic epilepsy and ragged-red fibre disease

Last reviewed 09/2021

MERRF is a maternally inherited neurodegenerative disorder.

Within an affected family, maternal relatives progress through the following stages of the disease:

  • myopathy
  • neurosensory deafness
  • myoclonic epilepsy
  • progressive dementia
  • hypoventilation
  • cardiac failure
  • renal failure
  • death

This degenerative neurological disease is caused by a maternally-inherited mutation at position 8344 in the mitochondrial genome. This point mutation disrupts the mitochondrial gene for tRNA-Lys and so disrupts synthesis of proteins essential for oxidative phosphorylation.

The clinical severity correlates with the loss of oxidative phosphorylation complexes in the mitochondria.