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Mitochondrial myopathies are a group of neuromuscular disorders. They are caused by mitochondria damage. Most of these disorders occur prior to age 20 and typically start with muscle weakness or exercise intolerance.
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What are the Disorders?
The disorders classified as mitochondrial myopathies include:
- Mitochondrial DNA depletion syndrome
- Mitochondrial neurogastrointestinal encephalomyopathy
- Progressive external ophthalmoplegia
- Leigh syndrome
- Kearns-Sayre syndrome
- Mitochondrial encephalomyopathy; lactic acidosis and stroke-like episodes
- Myoclonus epilepsy with ragged red fibers
- Ataxia, neuropathy and retinitis pigmentosa
- Pearson syndrome
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Changes, or mutations, in genes are the cause of mitochondrial myopathies. These disorders are inheritable. The genes involved in these disorders usually create the proteins that work inside the mitochondria. Proteins are organized into five complexes. The most common cause of one of these disorders is a deficiency in one or more of the complexes.
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Signs and Symptoms
The most common signs and symptoms of these disorders are weakness, fatigue and muscle wasting. The muscles responsible for controlling eyelid and eye movements are often affected. Some patients will experience mobility issues and may need a wheelchair to get around. Some patients experience difficulty swallowing food.
Some of the disorders may cause migraines and headaches or hearing impairments. Loss of vision is also possible.
Other possible issues include developmental delays in children, serious kidney problems, diabetes, gastrointestinal problems, rhabdomyolysis and myoglobinuria.
The disorder a person has will determine the symptoms he or she experiences.
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There is not specific course of treatment for this group of disorders. Dexterity may be improved and range of motion improved by physical therapy. Subjective improvement in energy levels and fatigue are seen in some patients with vitamin therapies, such as coenzyme Q10, riboflavin and carnitine.
If a patient experiences respiratory issues due to these disorders, respiratory care may be necessary. This may require a ventilator. In less severe cases, occasional pressurized air may be beneficial.
Some patients will experience heart-related issues and will need treatments for it. If a patient experiences what is known as a conduction block, which is a dangerous condition in which the rhythmic beating of the heart is interrupted. This is a treatable condition and most patients are successfully treated with a pacemaker. If cardiac muscle damage occurs, regular cardiologist examinations will be necessary to keep an eye on things.
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Prognosis varies greatly. It is largely dependent on the degree of organ involvement and the disorder the patient has. These disorders have the potential to cause progressive weakness and result in death.
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National Institute of Neurological Disorders and Stroke. (2007). NINDS Mitochondrial Myopathies Information Page. Retrieved on March 29, 2011 from the National Institute of Neurological Disorders and Stroke: http://www.ninds.nih.gov/disorders/mitochondrial_myopathy/mitochondrial_myopathy.htm
Muscular Dystrophy Association. (2011). Facts About Mitochondrial Myopathies. Retrieved on March on 29, 2011 from the Muscular Dystrophy Association: http://www.mdausa.org/publications/mitochondrial_myopathies.html