Mitochondrial Myopathies, Primary

Primary mitochondrial myopathies (PMMs) are a group of genetic diseases in which the mitochondria in the body's cells do not work properly. In PMMs, this has a major effect on a person's muscle strength and function. Mitochondria are tiny structures in the body where the chemical called ATP, the body's energy source, is made. Mitochondria are in cells throughout the body in organs that have high energy demands, such as the muscles, heart, and brain.

Mitochondrial DNA (mtDNA) and DNA in the rest of the body (nDNA) have instructions for genes and proteins that allow mitochondria to make enough energy for the body. mtDNA is passed from mother to child (not from father to child). nDNA is passed from both parents to their child. PMMs are caused by changes (or mutations) in mtDNA or nDNA genes.

Someone may be first thought to have a PMM by their symptoms and their family medical history. Symptoms can vary from person to person, even in the same family. Most often, symptoms of a PMM involve muscle weakness (myopathy), fatigue, exercise intolerance, and heart rhythm problems. Other symptoms can include trouble with balance or walking, difficulty with eating, and breathing problems.

Someone may also be diagnosed with a PMM by genetic testing that studies all their DNA for mutations. Genetic testing can confirm a diagnosis that is being considered based on a person's symptoms and family medical history.

PMMs are part of two larger groups of mitochondrial disease:

  • Mitochondrial diseases, primary (mitochondrial DNA-encoded)
  • Mitochondrial diseases, primary (nuclear DNA-encoded)

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