The same p.(Arg327Gln) variant had been reported in compound heterozygosity with the p.(Arg419Trp) variant in one individual with Combined oxidative phosphorylation deficiency‐21 (COXPD‐21; OMIM: 615918), a condition characterised by severe hypotonia, epilepsy and developmental delay without diabetes.10 The gene discussed is TARS2; the disease is hyperinsulinemic hypoglycemia, familial, 4.