Inheritance

For many patients mitochondrial diseases are inherited conditions that run in families. This can be particularly hard to understand if the disease has arisen in a child from two apparently healthy adults.

In order to understand how Mitochondrial Disease can be passed down through future generations it is important to first understand that there are two distinct types of DNA. Errors in either of these types of DNA can cause disease.

Mitochondrial Disease can be caused by a problem in either the mitochondrial DNA or the nuclear DNA and depending on where the error has arisen, this will determine how the condition has been inherited and the risk of passing it on.

To find out more about each type, please click below:

Mitochondrial DNA disease is caused by a mutation in your mitochondrial DNA.

Most cases of mitochondrial DNA disease will have been Maternally Inherited which means the mutation has been passed down from the mother to child. This is because we inherit our Mitochondrial DNA from our mothers only.

In this scenario, all children may have the mutation however some of the children may be severely physically affected and others not affected, due to the varying level of mutation passed down from the mother to different children.

Mitochondrial Diseases that can be inherited in this way include Leighs syndrome,  MELAS, MIDD, MERRF, NARP & LHON.

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It is also possible (although less likely) that mitochondrial DNA disease might have happened sporadically. In this situation the affected person will be the only person in their family to have disease and the mutation will have happened spontaneously during conception and not have been passed down from the mother.

Mitochondrial diseases that can be inherited in this way include Pearson's syndrome & Kearns-Sayre Syndrome.

Mitochondrial Disease may also be caused by a mutation in the nuclear DNA.

It is usually assumed that nuclear DNA mutations are responsible for disease once testing has ruled out errors in the mitochondrial DNA. Despite this, many families may still not know the name of the gene that caused the disease because even with sophisticated gene sequencing techniques, identification can be challenging.

Nuclear DNA Mutations may be inherited from parents in a number of different ways:

- Autosomal Recessive

- Autosomal Dominant

X-linked