Mitochondrial diseases are a group of disorders caused by damage to cell mitochondria, which are small structures or organelles located in human cells. Mitochondrial diseases result from failures of the mitochondria to convert food to energy. The result is decreased energy production. Mitochondria are responsible for creating more than 90% of the energy needed by the body to sustain life and support growth. When they fail, less and less energy is generated within the cell. Cell injury and even cell death follow.
Mitochondrial diseases appear to cause the most damage to nerve cells (neurons) of the brain, heart, liver, skeletal muscles, kidney and the endocrine and respiratory systems. Depending on which cells are affected, symptoms may include loss of motor control, muscle weakness and pain, gastro-intestinal disorders and swallowing difficulties, poor growth, cardiac disease, liver disease, diabetes, respiratory complications, seizures, visual/hearing problems, lactic acidosis, developmental delays and susceptibility to infection.
Mitochondrial disorders may be caused by mutations, acquired or inherited, in mitochondrial DNA (mtDNA) or in nuclear genes that code for mitochondrial components. They may also be the result of acquired mitochondrial dysfunction due to adverse effects of drugs, infections, or other environmental causes. Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function. The subclass of these diseases that have neuromuscular disease symptoms are often called a mitochondrial myopathy.
Treatment options are currently limited; vitamins are frequently prescribed, though the evidence for their effectiveness is limited. Pyruvate has been proposed recently as a treatment option. Another potential treatment procedure that has been successfully carried out on monkeys is spindle transfer, which is a genetic manipulation technique where the donor's mitochondrial DNA is not transferred to the receiving egg. Using a similar pronuclear transfer technique, researchers at Newcastle University successfully transplanted healthy DNA in human eggs from women with mitochondrial disease into the eggs of women donors who were unaffected.