MT-ND5 and Leber hereditary optic neuropathy: A total of five pathogenic secondary mutations are reported in three Serbian subjects harboring primary LHON mutations at nps, m.4216T>C (Y304H) in ND1, m.13708G>A (A458T) in ND5, m.15257G>A (D171N) and m.15812G>A (V356M) in CYB-MT which were all collectively found to be linked and in association with other homoplasmic mtDNA polymorphic changes at nps.