School of Medicine

Department of Genetics

MELAS Syndrome and MERRF Syndrome

Danielle Mercer1, Fern Tsien2, and Barbara Gordon-Wendt1

1 Department of Communication Disorders, LSUHSC School of Allied Health Professions
2 Department of Genetics, LSUHSC School of Medicine


MELAS and MERRF syndromes are two disorders caused by mitochondrial mutations.  These disorders are passed on from the mother, and cannot be inherited by the father.  In rare cases, a new mutation occurs in the child, which means it was not passed down from a parent.  The severity of these disorders can be very different, even between members of the same family.  MELAS and MERRF syndromes both affect many systems of the body, but especially the muscles, brain, and nervous system.  Sensorineural hearing loss can appear in both syndromes.  They are named after their most prominent features: 

MELAS (Mitochondrial encephalomyopathy, Lactic acidosis, and Stroke-like episodes)

MERRF (Myoclonic epilepsy with Ragged red fibers)

MELAS syndrome signs and symptoms:

  • muscle weakness and pain
  • recurrent headaches
  • seizures
  • vomiting
  • abdominal pain
  • hearing loss
  • stroke-like episodes

MERRF syndrome signs and symptoms:

  • muscle twitches
  • muscle weakness (abnormal muscle cells are ragged red figers)
  • recurrent seizures
  • uncoordinated movements
  • hearing loss
  • vision loss
  • heart abnormalities
  • short stature

For more information on MELAS and MERRF syndromes, visit the following links:

For information on patient support for MELAS and MERRF syndromes, visit the following links: