More than 90% of LHON cases across the world are due to three primary mutations (m.3460G>A in MT-ND1, m.11778G>A in MT-ND4, and m.14484T>C in MT-ND6) in mtDNA genes, encoding different subunits of complex I [2,4]. The gene discussed is MT-ND4; the disease is Leber hereditary optic neuropathy.