Deficiencies in mt-tRNAMet-formylation due to mutations in mitochondrial methionyl-tRNA formyltransferase (MTFMT, MIM: 611766) have been identified in a number of patients with Leigh syndrome and combined OXPHOS deficiency (Neeve et al 2013; Haack et al 2014). Here, MTFMT is linked to Leigh syndrome.