,8 Pathological variants of the core TIM23 complex subunits TIMM23 and TIMM17A/B have not yet been described, but several reported cases of pathogenic variants in TIMM50 have been connected to the mitochondrial disease 3-methylglutaconic aciduria, type IX (MGCA9; MIM: 617698) (Supplementary Table S1).9–14. This evidence concerns the gene TIMM50 and mitochondrial disease.