Mitochondrial diseases are generally congenital and can be caused by genetic defects in over 100 genes. The inheritance pattern may be very variable; there are dominant, recessive and spontaneous forms.
Furthermore, the small mitochondrial genome is necessary for the functioning of the mitochondrial metabolism. This genome is required exclusively for parts of the metabolism (complexes I, III, IV and V). As mitochondrial DNA is inherited almost exclusively from the egg cell, heed should be taken of a positive family medical history in the maternal line.
However, in paediatric forms of mitochondrial disorders, diseases in which the nuclear genome is affected predominate. Thus, an investigation of mitochondrial DNA is only advised where there is a conclusive suspected diagnosis or indicatory biochemical findings.