The mitochondrial myopathies are a group of diseases that particularly affect muscle but which may also affect other parts of the body, such as the brain and eyes. Some conditions classed as mitochondrial myopathies include:

  • Chronic Progressive Opthalmoplegia (CPEO)
  • Kearns-Sayre Syndrome (KSS)
  • Lactic Acidosis
  • Leigh’s disease
  • Mitochondrial Cytopathy
  • Mitochondrial Encephalopathy
  • Myoclonus Epilepsy Associated with Ragged-Red Fibres (MERRF)
  • Stroke-like episodes (MELAS)


Our bodies are made up of different types of tissue. Each tissue is composed of small cells and inside these are structures called mitochondria, which produce the energy for all the cells in the body. Mitochondria take in fuel from the food we eat, and burn it up to generate energy. If this process fails, the cell can’t function properly and this can lead to disease. As muscle and the brain require so much energy they are often the most severely affected types of tissue.

Mitochondrial myopathies affect people in different ways. The most common problems are a mild weakness of the arms and legs, and droopy eyelids. Some of the conditions affect the brain, which can cause epilepsy and progressive loss of memory.

The most common mitochondrial myopathy, Chronic Progressive External Opthalmolplegia, is usually only a mildly disabling disorder and doesn’t affect lifespan. Although there are no cures, many of the problems associated with mitochondrial myopathies can be treated effectively; for example muscle fatigue can be improved by gentle and regular exercise.

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