During 5 years observation of the patient with de novo 13042 G>A mutation in subunit ND5 of mitochondrial complex I (CI) and overlapping symptomatology of MELAS, MERRF, PEO (progressive external ophthalmoplegia) and finally of LHON (Leber’s hereditary optic neuropathy) was noticed. This evidence concerns the gene NDUFB6 and Leber hereditary optic neuropathy.