MT-ND4 and Leber hereditary optic neuropathy: In particular, mutations in the mitochondrial genes encoding the NADH dehydrogenase (ND) subunits 1, 4, and 6 (MT-ND1, MT-ND4, and MT-ND6, respectively) are the most frequent causes of LHON, accounting for more than 90% of LHON diagnosis in a Caucasian population [7, 8].