Patients with an older age at onset [OR (95% CI), 1.46 (1.12–1.91), P = 0.005] or higher mutation loads [OR (95% CI), 1.14 (1.03–1.26), P = 0.011] were more likely to present with LHON/LHON+ than with LS/LS+. Here, MT-ND4 is linked to Leber hereditary optic neuropathy.