The group of diseases, called mitochondrial myopathies, range from mild to life-threatening. All originate with problems in the mitochondria.

Mitochondria live in and provide energy to almost all cells. Mitochondrial myopathies, caused by genetic mutations, can harm many different bodily functions, but mainly impact muscles and nerves.

Mitochondrial Myopathy Symptoms

Generally, mitochondrial myopathies cause:

  • Muscle weakness or exercise intolerance
  • Lack of balance or coordination
  • Arrhythmias of the heart or heart failure
  • Problems with eye movements
  • Seizures
  • Stroke-like episodes
  • Vomiting
  • Cognitive or learning deficits
  • Dementia

Some symptoms appear with specific syndromes.

Kearns-Sayre syndrome (KSS):                   

  • Onset occurs before age 20             
  • Causes salt and pepper pigmentation in eye, eye movement problems (PEO), heart and skeletal muscle dysfunction

Leigh’s syndrome:                   

  • Onset occurs in infancy/ later           
  • Causes brain abnormalities that lead to muscle problems, seizures, uncoordinated muscle movement (ataxia), impaired vision and hearing, developmental delays and poor control over breathing

Mitochondrial DNA depletion syndrome:    

  • Occurs in infancy         
  • Causes muscle weakness and liver failure, floppiness, feeding difficulties and developmental delay

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS):  

  • Onset occurs from childhood to adulthood       
  • Causes stroke-like episodes, migraine headaches, vomiting and seizures, muscle weakness, exercise intolerance, hearing loss, diabetes and short stature

Myoclonic epilepsy associated with ragged red fibers (MERRF):     

  • Occurs in late childhood to adulthood   
  • Causes myoclonus (jerky movements), seizures, muscle weakness and uncoordinated muscle movement (ataxia)

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE):

  • Occurs before age 20 
  • Causes eye movement problems (PEO), drooping eyelid, limb weakness, digestive problems and peripheral neuropathy

Neuropathy, ataxia, and retinitis pigmentosa (NARP):

  • Occurs in early childhood or adulthood 
  • Causes uncoordinated muscle movement (ataxia) and degeneration of the retina in the eye, leading to loss of vision

Pearson’s syndrome:              

  • Occurs in infancy         
  • Causes severe anemia and pancreas problems
  • Survivors usually develop KSS

Progressive external ophthalmoplegia (PEO):  

  • Occurs in adulthood    
  • Causes eye movement difficulty and often symptoms of other mitochondrial diseases


We'll use some or all of these tests to diagnose you:

  • Muscle biopsy
  • Blood tests
  • Lumbar puncture (spinal tap)
  • Electrocardiogram
  • Electromyography (EMG)


Treatment focuses on symptom management.

Physical Therapy

Therapy may help you strengthen your muscles and improve mobility. You may need devices like braces, walkers or wheelchairs to help you get around.

Speech Therapy

Muscle weakness in the throat may make talking or swallowing difficult. Speech therapy can help strengthen the muscles or work around the weakness.

Respiratory Therapy

Respiratory therapy will help make sure you are breathing properly. It may involve some training techniques for respiratory muscles. It can include pressurized air treatment or the use of a ventilator.


Content was created using EBSCO’s Health Library. Edits to original content made by Rector and Visitors of the University of Virginia. This information is not a substitute for professional medical advice.