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)
Pronounced: My–toe-con-dree-al My-op-a-thee
by Patricia Griffin Kellicker, BSN
Definition
Mitochondrial myopathies are a group of diseases. Each disease has different symptoms. Some may be mild while other 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 very 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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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
- 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.
Tests may include the following:
- Muscle biopsy—to look for abnormal levels of mitochondria
- Blood test—to look for abnormal levels of certain enzymes and other substances
- Lumbar puncture (spinal tap) —to evaluate the fluid surrounding the brain and spinal cord
- Electromyography (EMG) and nerve conduction velocity (NCV)—to test nerve and muscle interaction
- Genetic test
- Eye exam
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
Medicines may be needed for symptoms such as seizures or pain.
RESOURCES:
Muscular Dystrophy Association
http://www.mda.org/
National Institute of Neurological Disorders and Stroke
http://www.ninds.nih.gov/
CANADIAN RESOURCES:
Canadian Institute of Health Research
http://www.cihr-irsc.gc.ca/
Muscle Dystrophy Canada
http://www.muscle.ca/
REFERENCES:
Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Neurology in Clinical Practice . 5th ed. Philadelphia, PA: Butterworth Heniemann Elsevier; 2008.
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 . Accessed December 27, 2012.
Fauci A, Harrison TR. Harrison's Principles of Internal Medicine . 17th ed. New York, NY: McGraw-Hill; 2008.
Jacobs L, Wert GD, Geraedts J, de Coo I, Smeets H. The transmission of OXPHOS disease and methods to prevent this. Hum Reprod Update . 2006;12(2):119-136.
Metabolic myopathies. American College of Rheumatology website. Available at: http://www.rheumat... . Accessed December 27, 2012.
Mitochondrial myopathies. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated November 7, 2012. Accessed December 27, 2012.
Mitochondrial myopathy. National Institute of Neurological Disorders and Stroke website. Available at: http://www.ninds.n... . Accessed December 27, 2012.
Last reviewed December 2012 by Mike Woods, MD
Last Updated: 12/27/2012