Primary mitochondrial myopathies (PMM) are a group of disorders that are associated with changes in genetic material (e.g. depletions, deletions, or mutations) found within the DNA of mitochondria (mtDNA) or with genes outside the mitochondria (nuclear DNA), affecting predominantly the skeletal muscle. Mitochondria, found by the hundreds within every cell of the body, regulate the production of cellular energy and carry the genetic blueprints for this process within their own unique DNA (mtDNA). These disorders often hamper the ability of affected cells to break down food and oxygen and produce energy. Mitochondria provide more than 90% of the energy used by the body’s tissues; mitochondrial disorders are characterized by a lack of sufficient energy for cells of the body to function properly. High-energy tissues like muscle, brain, or heart tissue are most likely to be affected by mitochondrial disorders. In most mitochondrial disorders, abnormally high numbers of defective mitochondria are present in the cells of the body. Mitochondrial diseases often affect more than one organ system of the body. Most mitochondrial diseases affect the muscles (myopathy). Sometimes, muscle disease is the only or predominant sign of a mitochondrial disorder, thus defined as PMM. There are no disease-modifying treatments for PMM; treatment is aimed to improving or resolving specific symptoms. (Content provided by NORD)
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