In many patients, mitochondrial disease is caused by an inherited gene mutation or multiple mutations.
In others, external environmental factors may be responsible for mitochondrial dysfunction.
Many different types of mito can develop in patients in contrasting ways. It often takes more work for healthcare teams to de!ne direct causes. Primary mitochondrial disease (PMD) exists from birth, and is genetic, meaning that the disease is inherited or passed down from one or both parents. In some rare cases, mito can be caused by a “spontaneous mutation”, meaning it occurs randomly at or before conception.
Within the mitochondria are two types of genetic material, mitochondrial DNA (mtDNA) and nuclear DNA (nDNA). mtDNA is passed on from the mother to her children, and nDNA is passed on from both parents.
Maternal inheritance is defined as a mother with a mitochondrial DNA (mtDNA) gene mutation that passes along the mutation to all of her children. Typically, all children will be affected but with varying degrees of severity, from no symptoms to severe disease. This does not mean that all of her children will be affected in the same way, and it is rarely possible to predict how children will be affected. This may cause stress for family planning.