The three primary mutations (m.3460G>A in the MT-ND1 gene, m.11778G>A in the MT-ND4 gene, and m.14484T>C in the MT-ND6 gene) on mitochondrial DNA (mtDNA) have been identified to be the essential factors for Leber hereditary optic neuropathy (LHON, OMIM 535000). Here, MT-ND4 is linked to Leber hereditary optic neuropathy.