In 1988, two research teams independently identified the first pathogenic mtDNA mutations: (1) a homoplasmic point mutation in MT-ND4 associated with Leber hereditary optic neuropathy (LHON) [19] and (2) large heteroplasmic deletions associated with mitochondrial myopathy [20]. This evidence concerns the gene MT-ND4 and Leber hereditary optic neuropathy.