Mitochondrial DNA m.3243A>G mutation in ethambutol-induced optic neuropathy: A case report

A 35-year-old man with maternally inherited diabetes presented with blurring of vision in both eyes for 6 months. He previously received antituberculous therapy including ethambutol (EMB) for 2 years. Temporal disc pallor and central scotomas were noticed in both eyes. P100 latency was delayed in visual evoked potential bilaterally. In addition, an elevated blood lactate concentration was observed. Interestingly, although EMB's potential optic neuropathy toxicity was our first consideration, a m.3243A>G mutation of mitochondrial DNA was found in the blood. Herein, we reported a young patient carrying a novel Leber's hereditary optic neuropathy mutation who developed EMB-induced optic neuropathy.