AARS2 and MTO1 mutations are preferentially associated with cardiomyopathy, mutations in TRMU present with infantile, reversible liver failure, YARS2 and PUS1 mutations lead to sideroblastic anaemia and myopathy, and RMND1 deficiency cause deafness, myopathy, renal involvement and a severe biochemical defect (Table 1). The gene discussed is MTO1; the disease is deafness.