Other clinical phenotypes associated with mutations in MTCO3 include Alzheimer’s disease, MELAS, Leigh syndrome, cardiomyopathy, exercise intolerance, myoglobinuria, myopathy, asthenozoospermia, failure to thrive, cognitive impairment, optic atrophy, encephalopathy, rhabdomyolysis, and sporadic bilateral optic neuropathy. Here, MT-CO3 is linked to Leber hereditary optic neuropathy.