Mitochondrial deafness

Non‐syndromic deafness can be caused by mutations in both nuclear and mitochondrial genes. More than 50 nuclear genes have been shown to be involved in non‐syndromic hearing loss, but mutations in mitochondrial DNA (mtDNA) might also cause hearing impairment. As mitochondria are responsible for oxidative phosphorylation, the primary energy‐producing system in all eukaryotic cells, mitochondrial dysfunction has pleiotropic effects. Many mutations in mtDNA can lead to multisystem disorders, such as Kearns–Sayre syndrome, NARP, MELAS, or MERRF syndromes, the presentation of which may include hearing loss. A more specific association of mitochondrially inherited deafness and diabetes known as MIDD syndrome can be caused by a limited number of specific mitochondrial mutations. In addition, several rare mutations in the mitochondrial MTTS1 and MTRNR1 genes have been found to be responsible for non‐syndromic hearing loss. The most frequent form of non‐syndromic deafness is presbyacusis, affecting more than 50% of the elderly. This age‐related hearing loss is a paradigm for multifactorial inheritance, involving a multitude of inherited and acquired mutations in the nuclear and mitochondria