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)
  • 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
    Torso muscle and nerves
    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 CONDITION AGE OF ONSET DEFINING SYMPTOMS
    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
    • Arryhthmias of the heart 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:
    Your heart activity may be tested. This can be done with an electrocardiogram.
    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:
    Work with your doctor on the 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 known guidelines to prevent this condition.
  • RESOURCES

    Muscular Dystrophy Association http://www.mda.org

    National Institute of Neurological Disorders and Stroke http://www.ninds.nih.gov

    CANADIAN RESOURCES

    Canadian Institutes of Health Research http://www.cihr-irsc.gc.ca

    Muscle Dystrophy Canada http://www.muscle.ca

    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%5Fmyopathies.html. Published December 2009. Accessed August 13, 2013.

    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/what.php. Updated November 7, 2012. Accessed August 13, 2013.

    NINDS mitochondrial myopathies page. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.nih.gov/disorders/mitochondrial%5Fmyopathy/mitochondrial%5Fmyopathy.htm. Updated December 16, 2011. Accessed August 13, 2013.

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