How does inheritance of a mitochondrial disease work?

Maternal and Regular: A few mitochondrial diseases are passed from the mother to all of her children. This is because certain mitochondrial genes are inherited from the mitochondria in the egg's cytoplasm (outside the "nucleus" that contains the regular genes). Other mitochondrial diseases are inherited the regular way, from the genes in the egg "nucleus" and in the sperm, that code for new mitochondria in the embryo.

Multifactorial: All of your mitochondria come from the mother. Control of mitochondrial function is, however, influenced by nuclear DNA (the DNA that comes from both parents). Abnormal mitochondria present in the egg can randomly segregate during cell division and embryogenesis so that many or few organ systems are involved. The impact depends on the proportion of abnormal mitochondria and the locations. http://www.umdf.org/site/c.8qKOJ0MvF7LUG/b.7934627/k.3711/What_is_Mitochondrial_Disease.htm