Mitochondrial Myopathy
En Español (Spanish Version)

Definition
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

Mitochondrial myopathies decrease the ability of nerves and muscles. Weakness and uncoordinated movement may result.
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Causes
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.

Symptoms
Mitochondrial myopathies can cause a range of symptoms. Symptoms by specific condition include:

NAME OF CONDITIONAGE OF ONSETDEFINING SYMPTOMSKearns-Sayre syndrome (KSS)Before age 20Salt and pepper pigmentation in eye, eye movement problems (PEO), heart and skeletal muscle dysfunctionLeigh’s syndromeInfancy—can appear laterBrain abnormalities that lead to muscle problems, seizures, uncoordinated muscle movement (ataxia), impaired vision and hearing, developmental delay, and poor control over breathingMitochondrial DNA depletion syndromeInfancyMuscle weakness and liver failure, floppiness, feeding difficulties, and developmental delayMitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS)Childhood to adulthoodStroke-like episodes, migraine headaches, vomiting and seizures, muscle weakness, exercise intolerance, hearing loss, diabetes, short statureMyoclonic epilepsy associated with ragged red fibers (MERRF)Late childhood to adulthoodMyoclonus (jerky movements), seizures, muscle weakness, uncoordinated muscle movement (ataxia)Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE)Before age 20Eye movement problems (PEO), drooping eyelid, limb weakness, digestive problems, peripheral neuropathyNeuropathy, ataxia, and retinitis pigmentosa (NARP)Early childhood to adulthoodUncoordinated muscle movement (ataxia), degeneration of the retina in the eye leading to loss of visionPearson’s syndromeInfancyCauses severe anemia and pancreas problems, survivors usually develop KSSProgressive external ophthalmoplegia (PEO)AdulthoodEye 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
Diagnosis
Your doctor will ask about your symptoms and medical history. A physical exam will be done. You will also be asked about any family history of the disease. An eye exam may also be done.

Your bodily fluids and tissues may be tested. This can be done with:

  • Muscle biopsy
  • Blood tests
  • Lumbar puncture —to evaluate the cerebrospinal fluid that protects the brain and spinal cord
Your heart's electrical activity may be tested. This can be done with an electrocardiogram (EKG).

Your nerve function may be tested. This can be done with electromyography (EMG).

Treatment
There is no specific treatment for these diseases. Instead, treatment will focus on managing the symptoms. Treatment options include the following:

Dietary Supplements
Supplements may help make energy in the cells. These may include:

Your doctor will work with you on the proper doses of these supplements.

Physical Therapy
Therapy may be used to strengthen muscles and improve mobility. Some may need devices like braces, walkers , or wheelchairs to help them get around.

Speech Therapy
Muscle weakness in the throat may make talking or swallowing difficult. Speech therapy may 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.

Medications
Medications may be needed for symptoms such as seizures or pain.

Prevention
There are no current guidelines to prevent mitochondrial myopathies. If you have a family history of the disorder, you can talk to a genetic counselor when deciding whether to have children.




RESOURCES:
Muscular Dystrophy Association

National Institute of Neurological Disorders and Stroke

CANADIAN RESOURCES:
Canadian Institutes of Health Research

Muscle Dystrophy Canada

References:
DiMauro S. Pathogenesis and treatment of mitochondrial myopathies: recent advances. Acta Myol. 2010;29(2):333-338.

Facts about mitochondrial myopathies. Muscular Dystrophy Association website. Available at: http://www.mda.org/publications/mitochondrial_myopathies.html. Published December 2009. Accessed August 20, 2014.

Jacobs L, Wert GD, et al. The transmission of OXPHOS disease and methods to prevent this. Hum Reprod Update. 2006;12(2):119-136.

Mitochondrial myopathies. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated December 2, 2013. Accessed August 20, 2014.

NINDS mitochondrial myopathies page. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/mitochondrial_myopathy/mitochondrial_myopathy.htm. Updated December 16, 2011. Accessed August 20, 2014.

Last Reviewed August 2014



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