Lake et al. concluded that the p.Arg225* TIMMDC1 nonsense variant was hypomorphic and an unlikely contributor to pathogenesis in a patient with Leigh syndrome, given that the presence of truncated TIMMDC1 protein had almost no effect on mitochondrial complex I assembly and activity in patient fibroblasts homozygous for the variant21. Here, TIMMDC1 is linked to Leigh syndrome.