Mitochondrial Myopathy

(Kearns-Sayre Syndrome; Leigh’s Syndrome; Mitochondrial DNA Depletion Syndrome; Mitochondrial Encephalomyopathy, Lactic Acidosis and Strokelike Episodes; Myoclonic Epilepsy Associated With Ragged Red Fibers; Mitochondrial Neurogastrointestinal Encephalopathy; Neuropathy, Ataxia, and Retinitis Pigmentosa; Pearson’s Syndrome; Progressive External Ophthalmoplegia)


Mitochondrial myopathies are a group of diseases. Each disease has different symptoms. Some may be mild while others are life threatening. However, the diseases are all caused by a problem with the mitochondria.Mitochondria are tiny structures found in almost all cells. It is their job to provide energy to these cells. Mitochondrial myopathies can interfere with many different bodily functions. It tends to have the greatest impact on structures that are active, such as the muscles and nerves.
Muscular and Nervous Systems
Torso muscle and nerves
Mitochondrial myopathies decrease the ability of nerves and muscles. Weakness and uncoordinated movement may result.
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This condition is caused by a mutation in a specific gene.

Risk Factors

Having a family member with the mutated gene increases the risk of mitochondrial myopathies.


Mitochondrial myopathies can cause a range of symptoms. Symptoms by specific condition include:
Kearns-Sayre syndrome (KSS) Before age 20 Salt and pepper pigmentation in eye, eye movement problems (PEO), heart and skeletal muscle dysfunction
Leigh’s syndrome Infancy—can appear later Brain abnormalities that lead to muscle problems, seizures, uncoordinated muscle movement (ataxia), impaired vision and hearing, developmental delay, and poor control over breathing
Mitochondrial DNA depletion syndrome Infancy Muscle weakness and liver failure, floppiness, feeding difficulties, and developmental delay
Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) Childhood to adulthood Stroke-like episodes, migraine headaches, vomiting and seizures, muscle weakness, exercise intolerance, hearing loss, diabetes, short stature
Myoclonic epilepsy associated with ragged red fibers (MERRF) Late childhood to adulthood Myoclonus (jerky movements), seizures, muscle weakness, uncoordinated muscle movement (ataxia)
Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) Before age 20 Eye movement problems (PEO), drooping eyelid, limb weakness, digestive problems, peripheral neuropathy
Neuropathy, ataxia, and retinitis pigmentosa (NARP) Early childhood to adulthood Uncoordinated muscle movement (ataxia), degeneration of the retina in the eye leading to loss of vision
Pearson’s syndrome Infancy Causes severe anemia and pancreas problems, survivors usually develop KSS
Progressive external ophthalmoplegia (PEO) Adulthood Eye movement difficulty, and often symptoms of other mitochondrial diseases, but can be an independent syndrome
Other general symptoms include:
  • Muscle weakness or exercise intolerance
  • Lack of balance or coordination
  • Heart arryhthmias or heart failure
  • Problems with eye movements—either problems with control or inability to move them
  • Seizures
  • Stroke-like episodes
  • Vomiting
  • Cognitive or learning deficits
  • Dementia

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