LHON

Risk of eyesight loss


If someone has inherited a LHON gene, it does not mean that they will definitely lose their eyesight. No-one can predict which people with a LHON gene will lose their eyesight.

We do not yet know what extra factor triggers LHON in someone who has a LHON gene. There have been some studies of families of LHON patients, analysing how many people in the family actually develop symptoms. These figures allow scientists to estimate how likely it is that someone who has a LHON gene will develop symptoms of LHON. These figures are estimates of risk based on statistics, not predictions for any particular family.

Some published reports say that the risk of developing symptoms is higher, especially for males with an affected close relative (between 50 and 80 %). The figures on this page are those proposed by OMIM as the best estimate so far available.

Estimated risk of eyesight loss for a male with a LHON gene

It is estimated that about 20% (1 in 5) men with a LHON gene will develop symptoms of LHON.

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Estimated risk of eyesight loss for a female with a LHON gene

It is estimated that about 4% (1 in 25) women with a LHON gene will develop symptoms of LHON.

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The following figures are from a paper by A. Harding et.al. published in the American Journal of Human Genetics, 1995 v57 p77



Risk of eyesight loss for the brother of an affected person

It is estimated that about 25% (1 in 4) brothers of people affected by LHON will also develop symptoms of LHON.

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Risk of eyesight loss for the sister of an affected person

It is estimated that about 8% (1 in 12) sisters of people affected by LHON will also develop symptoms of LHON.

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Risk of eyesight loss for the nephew of an affected person

It is estimated that about 41% (2 in 5) nephews of people affected by LHON will also develop symptoms of LHON. Note that this can only apply to sons of sisters, not sons of brothers. Nephews who are the son of a brother of the affected person cannot inherit the LHON gene.

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Risk of eyesight loss for the niece of an affected person

It is estimated that about 17% (1 in 6) nieces of people affected by LHON will also develop symptoms of LHON. Note that this only applies to daughters of sisters, not daughters of brothers. A niece who is the daughter of the brother of an affected person cannot inherit the LHON gene.

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This page last updated 1 July 2001 Copyright © Jim Leeder 1997-2001