MT-ND4 and Leber hereditary optic neuropathy: LHON is a primary mitochondrial genetic disorder that affects approximately 1 in 30,000 people in the population and three point mutations within the mitochondrial genome account for over 90 % of cases, namely m.3460G>A (MTND1), m.11778G>A (MTND4) and m.14484T>C (MTND6) [87].