ACO2-related optic atrophy with or without extraocular features (MONDO_1060120, a Monarch Disease Ontology identifier) is an optic atrophy in which the cause of the disease is monoallelic or biallelic variants in the ACO2 gene. ACO2 is a mitochondrial protein and thus, in addition to the optic atrophy features, features of this disease include abnormal mitochondrial morphology and can affect other organ systems. Extraocular features can include ataxia, spastic paraplegia, CNS abnormalities, neurodevelopmental phenotypes, and retinal degeneration.