Optic atrophy and optic neuropathy are commonly associated with other mitochondrial disease pathologies implicating CI deficiency, including Leber hereditary optic neuropathy (Carelli et al, 2023) as well as recessively-inherited variants in structural components of CI such as NDUFS6 (Gangfuss et al, 2024), the CI assembly factor TMEM126A (Formosa et al, 2021) and DNAJC30 which mediates CI repair (Stenton et al, 2021). Here, TMEM126A is linked to inborn mitochondrial metabolism disorder.