[Leber's hereditary optic atrophy. A hereditary disease caused by mitochondrial DNA mutation]

Leber's hereditary optic neuropathy is a genetic disorder characterized by sudden bilateral loss of vision. It is transmitted exclusively through females (matroclinous inheritance) due to a mutation in mitochondrial DNA (mtDNA), most frequently a GC----AT substitution of base pair no. 11778 ('The Wallace mutation'). All children of homoplasmic female carriers inherit the disease gene. Penetrance is incomplete, but high in males. Genetic heterogeneity has been reported, as has heteroplasmy. The nature of the mutation and the degree of heteroplasmy have prognostic value, and genetic counselling as well as clinical evaluation should therefore include mtDNA analysis. Diagnostic mtDNA analysis is illustrated for three Danish patients, one of whom is without known affected relatives. All three were homoplasmic for the Wallace mutation. Neither prophylaxis nor therapy, by medication are possible as yet. Loss of vision may be prevented, or delayed, if at-risk individuals refrain from smoking and consumption of certain foodstuffs.