Mitochondria are the energy factories of cells and carry some of their own genes. When mitochondria stop working properly, less and less energy is generated within the cells. This may lead to cell injury or even cell death, and body systems, often including the muscles, will not function properly. Mitochondrial myopathies can be inherited through faulty genes within the mitochondria themselves or through genes within the cell nucleus.
Mitochondrial myopathies can cause increasing weakness in one or a few muscle groups, such as the eye muscles (ophthalmoplegia) and often affect many other organs, such as the heart, intestines, or brain. Infants whose muscles are affected are weak and have severely reduced muscle tone (hypotonia, or "floppiness"). Depending on which organs are affected, complications may include deafness or hearing loss, seizures, or stroke-like episodes. One mitochondrial myopathy is called Kearns-Sayre syndrome. It causes problems with the eyes, muscles, and heart.
(See also Mitochondrial Disorders.)
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
Muscular Dystrophy Association: Information on research, treatment, technology, and support for people living with a mitochondrial myopathy