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Mitochondrial Myopathy 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

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
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.

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 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.rheumatology.org/public/factsheets/diseases_and_conditions/metabolicmyopathies.asp?aud=pat . 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.nih.gov/disorders/mitochondrial_myopathy/mitochondrial_myopathy.htm . Accessed December 27, 2012.

Last reviewed December 2012 by Mike Woods, MD

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