The literature emphasizes that more than 90% of all patients with LHON (about 70% in Northern Europe) have one of the following three pathogenic variants: m.11778G > A (MT-ND4), m.14484T > C (MT-ND6), or m.3460G > A (MT-ND1) [1,6,24,29,30,31,32,33,34], but in our study in Lithuania, in patients with LHON > 18 years, these main mutations were detected only in 33.4%. The gene discussed is MT-ND6; the disease is Leber hereditary optic neuropathy.