The heteroplasmic mutation of NC_012920.1: m.3697G>A, p.(Gly131Ser) in the mitochondrial NADH dehydrogenase subunit 1 (MTND1, OMIM #516000) gene was identified in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke‐like episodes (MELAS) (Kirby et al., 2004), Leber's hereditary optic neuropathy (LHON) (Spruijt et al., 2007), LHON/MELAS overlap syndrome (Blakely et al., 2005), and Stüve‐Wiedemann syndrome (Morava, Hamel, Hol, Rodenburg, & Smeitink, 2006). The gene discussed is MT-ND1; the disease is Leber hereditary optic neuropathy.