Leber hereditary optic neuropathy (LHON) is a rare, chronically damaging mitochondrial hereditary disease, which usually leads within a year to a marked painless reduction in vision or a practical blindness. There is a degeneration of the retinal ganglion cells of the optic nerve.
In some cases, the patients also have a color vision disorder. Often, the symptoms appear unilaterally, then bilaterally over weeks to months. However, the mitochondrial changes may also manifest in the cells of the cardiac conduction system and in this case show cardiac arrhythmias.
Rarely found in LHON patients other neurological abnormalities, especially movement disorders such as tremor, ataxia and dystonia. Typically affected are young men who are on average between 15 and 35 years old at the onset of the disease (acute phase). Other maternal family members may also be affected by the disease.
The cause of the disease are point mutations of mitochondrial DNA (mtDNA). These concern mtDNA gene loci encoding mitochondrial enzymes and respiratory chain proteins that cause mis-expression with concomitant loss of function of their gene products.
The probability of falling ill is additionally influenced by environmental factors, eg. For example, strong cigarette smoking as a proven risk factor for an increased risk of disease could be detected. The most important differential diagnosis to LHON is optic neuritis, e.g. in multiple sclerosis.
The prognosis of the disease is determined by the age at onset of symptoms (younger patients have a more favorable prognosis) and by the causative mutation.