Information in english

What is LHON?

LHON or Leber’s hereditary (genetic) Opticus (optic nerve), neuropathy (nerve damage) will often manifest itself when a person is in his/her 20´s to 40´s with a fast onset of severe vision loss in the center of the visual field. The sight is blurry or disappears in the middle of the visual field. Most often, the person will maintain the peripheral vision, but in some cases the disease leads to total blindness.

LHON is a hereditary disease caused by a mutation in mitochondrial DNA. Mitochondria convert nutrients into energy in the body’s cells. Those who carry a LHON mutations is at risk to suffer of a situation where the mitochondria are not able to provide the optic nerve with enough energy. The optic nerve becomes weakened and because of that is not able to transfer vision input to the brain.

There can be many thousands of mitochondria in a single cell. The accompanying illustration shows the mitochondrial sections.

Heredity

The mitochondria are only inherited from the mother. Men carrying the mutation therefore does not pass it on to their children. A woman who carries the mutation transfers it to all her children, but all individuals that are carrying the mutation does not suffer from LHON.

Approximately 50% of men and 15% of women who carry the mutation develop the disease. It is not yet known why more men than women are affected, but some researchers believe that the female sex hormone may have a protective effect.

The percentage of mutated mtDNA can also vary. Usually 100% of the relevant variant of mtDNA mutated, but sometimes only a certain part is mutated. People who have less than 60% mutated mtDNA is at a much lower risk of developing the disease.

A rare disease

It is not clear how common LHON mutations is because not everyone who carries it get affected. Between 100-200 people have developed the disease in Sweden. It is also not yet known what it is that makes some people with the mutation develop the disease while most do not.

Since LHON is such a rare disease, our organization is a member of Riksförbundet Sällsynta Diagnoser (Rare diseases Sweden).

Likely triggering factors

It has been established that smoking can be a trigger. People who know they carry the mutation should avoid smoking and all forms of smoke. Large amounts of alcohol, and mental stress are other factors that scientists believe may contribute as triggers to the disease. There are also certain medications (eg certain antibiotics like Tetracycline, Streptomycin, Erythromycin and Minocycline) that is believed to trigger the disease. Under section 5 on this link: lhon.org is a longer list in English of medications, etc. which some scientists believe could trigger the disease and therefore should be avoided if it is known that a persone carries the mutation.

No cure yet, but research is moving forward!

LHON is not yet curable. Research has shown that a very high dose of an artificial form of Q10, Idebenone, can in some cases provide a small improvement, or at least function as a temporary inhibiting drug. But Idebenone has to be taken in very high doses and it does not work for all people. The situation is complicated by the existence of several different LHON mutations. There are three mutations of mitochondrial DNA (mtDNA), which is most common among those suffering from LHON called G11778A, G3460A and T14484C. In Sweden G11778A is the most common.

LHON in very rare cases also occur in other parts of the body than the optic nerve. Among other things, patients can suffer from MS or an MS-like disease, as well as heart problems. The disease is then called LHON Plus.