Mitochondrial myopathies are a group of neuromuscular diseases caused by damage to the mitochondria. Mitochondria are small, energy-producing structures that serve as the cells’ power plants. Nerve cells in the brain and muscles require a great deal of energy, and thus appear to be particularly damaged when mitochondrial dysfunction occurs.
Some of the more common mitochondrial myopathies include:
- Kearns-Sayre syndrome
- Myoclonus epilepsy with ragged-red fibers
- Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes
Most mitochondrial myopathies occur before the age of 20, and often begin with exercise intolerance or muscle weakness. During physical activity, muscles may become easily fatigued or weak. Muscle cramping is rare, but may occur. Nausea, headache, and breathlessness are also associated with these disorders. Inheritance is maternal.
The symptoms of mitochondrial myopathies include:
- Muscle weakness
- Exercise intolerance
- Heart failure or rhythm disturbances
- Dementia
- Movement disorders
- Stroke-like episodes
- Deafness
- Blindness
- Droopy eyelids
- Limited mobility of the eyes
- Vomiting
- Seizures
The prognosis for patients with mitochondrial myopathies varies greatly, depending largely on the type of disease and the degree of involvement of various organs. These disorders cause progressive weakness and can lead to death.
Although there is no specific treatment for any of the mitochondrial myopathies, physical therapy may extend the range of movement of muscles and improve dexterity. Vitamin therapies such as riboflavin, coenzyme Q, and carnitine (a specialized amino acid) may provide subjective improvement in fatigue and energy levels in some patients.
No cure currently exists, although there is some hope for a treatment for this whole class of hereditary diseases with the use of an embryotic mitochondrial transplant.