Mitochondrial Myopathy

What is mitochondrial myopathy?

Mitochondrial myopathies are a set of disorders involving abnormalities in mitochondria, which are structures within cells that are responsible for using oxygen to produce energy — often described as the powerhouses of the cells. Therefore, mitochondrial myopathies most commonly affect organs that consume a lot of oxygen such as muscles, the brain, and the heart.

Symptoms may vary, but typically include muscle pain or weakness,double vision or blurry vision, droopy eyelids, difficulty breathing, and, in some forms, blindness, and seizures.

Treatment options include exercise, possible supplements, as well as procedures and assistive devices to address eye and breathing issues.

Make an appointment with a physician to further analyze what genetic defects may be present, and begin prescription treatment.

Mitochondrial myopathy symptoms

Because mitochondrial myopathies refer to a set of disorders, the symptoms will vary depending on the specific disorder.

Main symptoms

Symptoms that may be seen in various mitochondrial myopathies include:

• Muscle pain or weakness: The defining symptom of mitochondrial myopathies is muscle pain (myalgia) or weakness. The muscle symptoms more often affect the upper arms or thighs but can also affect the forearms or lower legs. These symptoms can develop rapidly or gradually.
• Double vision, droopy eyelids, or blurry vision: These are commonly seen in Chronic Progressive External Ophthalmoplegia and Kearns-Sayre Syndrome. These symptoms occur because the disorder affects the muscles responsible for moving the eyes and lifting the eyelids.
• Difficulty breathing: This can occur if the muscles responsible for breathing become weakened.

Other symptoms

Some forms or mitochondrial myopathies can include the following.

• In infants: These symptoms may include poor attention, difficulty feeding, and weak muscles with floppy muscle tone.
• Jerky contraction of muscles: This is known as myoclonus. This is classically seen in a disorder called Myoclonic Epilepsy with Ragged Red Fibers.

Stroke-like symptoms

Some forms of mitochondrial myopathies can cause stroke-like episodes. This is classically seen in a disorder known as Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS). These episodes usually develop in childhood and often recur, leading to progressive neurological dysfunction. Symptoms occur suddenly and include:

• Numbness or weakness
• Blindness
• Seizures

Mitochondrial myopathy causes

Mitochondrial myopathies are caused by mutations in genes important for normal function of the mitochondria. Different mutations in various genes can result in disorders that all fall under the category of mitochondrial myopathies. Specific types of mutations include those in nuclear DNA, mitochondrial DNA, as well as mitochondrial depletion.

Mutations in nuclear DNA

All cells carry DNA in a structure in the center of the cell called the nucleus, and that DNA carries genes that provide instructions for important functions. Mutations in these genes can produce mitochondrial myopathies that cause isolated myopathies (only muscle symptoms, no other symptoms), as well as disorders such as Chronic Progressive External Ophthalmoplegia and Kearns-Sayre Syndrome, which primarily affect the eyes.

Mutations in the mitochondrial DNA

Mitochondria have their own DNA that is separate from the DNA carried in the nucleus. Mitochondrial myopathies caused by mutations in mitochondrial DNA can only be transmitted from the mother to her child because this type of DNA only comes from mothers. Mutations in mitochondrial DNA are responsible for disorders such as MELAS and Myoclonic Epilepsy with Ragged Red Fibers. Mutations in mitochondrial DNA can also cause Chronic Progressive External Ophthalmoplegia and Kearns-Sayre Syndrome.

Mitochondrial depletion

Some syndromes are associated with mitochondrial depletion, in which the mitochondrial DNA is not properly maintained and breaks down. Mitochondrial depletion is responsible for several mitochondrial myopathies, including a set of disorders that cause severe brain symptoms in infants and children.

Treatment options and prevention for mitochondrial myopathy

Mitochondrial myopathy is a chronic disorder that cannot be cured. Therefore, treatment is focused on reducing symptoms and treating associated disorders. Specific treatments options include exercise, supplements, medications to prevent seizures, and surgery and various assistive devices for associated eye and breathing issues.

Exercise

Exercise has been shown to be beneficial for people with mitochondrial myopathies by increasing mitochondrial function. These include:

• Aerobics: Such as running, biking, or swimming
• Resistance training: Such as weight lifting or body-weight exercises

Supplements

Physicians may recommend that people with mitochondrial myopathies try these treatments, as they may help; although studies have not yet shown definite benefit.

Supplements to improve mitochondrial function and currently being studied include:

• Coenzyme Q10: An important protein in mitochondrial function
• Antioxidants: Such as idebenone (Catena)
• Creatine and L-carnitine: Naturally occurring substances that are found in abnormally low levels in people with mitochondrial myopathies

When to seek further consultation for mitochondrial myopathy

If you develop any symptoms of mitochondrial myopathies, such as muscle pain or weakness, double vision or droopy eyelids, or neurological symptoms, you should see your physician. He or she can order tests including specific genetic tests to determine if you have a mitochondrial myopathy.

If someone in your family has been diagnosed with a mitochondrial myopathy

You should consider going to see your physician, even if you do not have symptoms. Your physician may order genetic tests to determine if you have inherited a mitochondrial myopathy.