MT-ND4 and Leber hereditary optic neuropathy: One of three primary mutations m.3460G>A, m.11778G>A and m.14484T>C respectively affecting the MT-ND1, MT-ND4 and MT-ND6 subunit genes of NADH dehydrogenase (complex I) are present in more than 90% of all LHON cases18,19.