Mitochondria and Leber's hereditary optic neuropathy

Leber's hereditary optic neuropathy, a disease which often occurs in young men, causes bilateral loss of central vision. Visual deterioration is progressive, first in one eye, then the other, usually over a period of days to weeks. Recently it was shown that this condition is caused by a mutation of mitochondrial deoxyribonucleic acid (mtDNA). Mitochondria, small structures within the cytoplasm that function in cell metabolism, contain a source of DNA. MtDNA is inherited exclusively from the mother and represents a unique inheritance pattern. For visual loss to occur a substantial percent of mtDNA molecules must be mutant. Sporadic cases of Leber's hereditary optic neuropathy may occur in patients whose maternal ancestors have heteroplasmy (both mutant and normal molecules). It is difficult to explain why all people with predominantly mutant mtDNA molecules do not lose their vision. The importance of heteroplasmy in Leber's patients and the discovery that the proportion of normal and mutant cells can change rapidly underscore the need for mtDNA analysis in order to improve genetic counseling for these patients and their families. (Consumer Summary produced by Reliance Medical Information, Inc.)