Mitochondrial Diseases, Primary (mitochondrial DNA-encoded)

Primary mitochondrial diseases (PMDs) are a group of genetic diseases in which the mitochondria in the body's cells do not develop or work properly. 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) has 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). Mitochondrial DNA-encoded PMDs (mtDNA PMDs) are caused by changes (or mutations) in mtDNA genes. People with these diseases represent about 30% of all people with mitochondrial diseases.

Someone may be first thought to have a mtDNA PMD by their symptoms and their family medical history. Symptoms can vary from person to person, even in the same family. mtDNA PMDs usually progress over time and affect multiple organs in the body. Common symptoms include fatigue, muscle weakness, stroke, vision loss, heart rhythm problems, abnormal digestive system movement, and lactic acidosis (a buildup of lactic acid in the body).

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

Within mtDNA PMDs are two different groups of mitochondrial disease:

  • Mitochondrial respiratory chain disorders (MRCDs)
  • Mitochondrial myopathies, primary (PMMs)

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