MT-RNR1 and deafness: Mitochondrial forms of HL are associated with a pathogenic variants in the genes: MT-RNR1 (OMIM:561000), MT-TS1 (OMIM:590080), MT-CO1 (OMIM:516030), MT-TH (OMIM:590040), MT-ND1 (OMIM:51600), MT-TL1 (OMIM:590050), MT-TE (OMIM:590025) and MT-TK (OMIM:590060), which can lead to both isolated HL and various syndromes, when HL can be combined with the endocrine (diabetes mellitus and deafness, OMIM:520000) and nervous system pathologies (MERRF syndrome, OMIM:545000 and MELAS syndrome, OMIM:540000)5.