Mitochondrial disorders can be passed on in families in different ways. The inheritance pattern depends on the disorder and whether the genetic change is in the nDNA or mtDNA. A patient’s family history can give clues about the inheritance pattern for a specific condition in a family.
Some mitochondrial diseases follow maternal inheritance. This means that the condition is passed down on the mother’s side of the family. Only conditions caused by mutations in the mtDNA follow maternal inheritance. In this type of inheritance, all the children of an affected mother are at risk to inherit the mutation, but it is difficult to predict if the children will develop the disorder. Fathers who have the disorder do not pass it on to children. This is because mitochondria are passed on from the mother in the egg cell during fertilization.
Autosomal Recessive Inheritance
Some conditions follow autosomal recessive inheritance. This means that the condition is inherited from both parents. Both parents are healthy, but are carriers of the mutation. If they both pass their copy of the mutation on to a child, then the child could be affected.
Autosomal Dominant Pattern
Other mitochondrial disorders can be inherited in an autosomal dominant pattern. This means that a person can have the condition if they inherit a mutation from one parent. The parent they inherited the mutation from often shows signs of the disorder.
Some mitochondrial disorders can be inherited in an X-linked pattern. This means that a healthy mother can pass the condition on to her sons, but not to her daughters.
In some conditions, the genetic mutations that cause the disease are usually not inherited. In those cases, the mutation is new, or sporadic, in that person.
It is important to talk with your doctor or genetic counselor about your family history.