Maternal Bloodline Inheritance
Being diagnosed with a mitochondrial mutation known to be pathogenic for LHON means that you suddenly know that everyone on your maternal bloodline including your mom, her siblings, the children of your maternal aunts, your siblings, your children and future children (if you’re a woman) and your sisters’ current and future children very likely carry the same LHON mutation. Because it is almost always passed from a mother to all her children, it’s generally clear who carries it without the need for additional genetic tests, though people may choose to have their own testing done.
Mitochondrial DNA is only inherited from the mother:
It can be awkward to tell extended family members that they likely carry an LHON gene mutation. The Telling Family About LHON Risk video gives guidance on how to have this conversation. Telling them means that they suddenly need to worry about the potential of sudden vision loss, and that is difficult information to share and receive. The LHON Runs in the Family video can be provided to family members on the maternal bloodline. Sharing the information allows family members to become aware of environmental factors that are believed to impact the risk of vision loss among carriers of an LHON mutation, such as inhaling smoke, drinking alcohol, and taking certain antibiotics. Prevention may be their best opportunity to reduce the risk of LHON vision loss, and knowledge is power.
Individuals known or presumed to have an LHON mutation, without vision loss, are referred to as “carriers” or as “unaffected carriers.” Both the LHON Carrier Checklist webpage and video explain important steps LHON carriers may wish to take. This may or may not include getting genetic testing. Developing relationships with medical professionals familiar with LHON can be helpful in obtaining baseline testing of the optic nerves and in expediting the path to care if onset should ever begin.
If an unaffected carrier is informed of the situation and begins to lose vision, they'll know that it’s likely due to LHON and can avoid weeks and months of unnecessary, costly, and invasive tests and treatments as well as the mental anguish of the unknown. Initiating treatment, if available, may be most effective when started as soon as possible after onset. If someone has been made aware that they carry an LHON mutation, then they can immediately seek medical care, treatment options, and information about any clinical trials from an informed medical professional if they do start losing vision.
LHON can be a good reason to delve into the family’s genealogy. It can be interesting to trace the maternal line through all the women who likely carried and passed the LHON gene, and the men who carried but didn’t pass it on. A professional genealogist analyzed several LHON families, and explained how to study your own maternal bloodline in the LHON Genealogy Project video.
Because there is usually a clear pattern of genetic inheritance when an LHON mitochondrial mutation has been identified, those with a family member on the maternal inheritance bloodline with an LHON mutation should expect that any sudden, painless central vision loss they experience is likely caused by LHON and quickly have an examination of the optic nerves for confirmation.
