Non-syndromic mitochondrial hearing loss

Pathology that causes hearing loss due to the presence of pathogenic variants in certain genes of the mitochondrial DNA.

Hearing loss is a common pathology in which it is estimated that in 50% of cases it is due to genetics. It involves alterations in both nuclear DNA and mitochondrial DNA.

Nonsyndromic deafness is a partial or total loss of hearing that is not associated with other signs and symptoms. The causes are complex, and more than 90 genes have been identified as being involved. Depending on their genetic origin, there are several types, including mitochondrial deafness. The altered mitochondrial DNA is inherited from mothers to all children, not inherited from affected fathers.

One of the genes that is usually mutated in nonsyndromic mitochondrial deafness is 12S rRNA and the most frequently detected variant is m.1555A>G.

Symptoms

Hearing loss in both ears (bilateral) is usually severe-profound and is induced by treatment with aminoglycoside antibiotics and occurs within days to weeks after administration of the drug (including a single dose). These antibiotics include: gentamicin, tobramycin, amikacin, kanamycin or streptomycin.

Cases have been described of individuals who are carriers of pathogenic variants related to this type of deafness who may develop the pathology without having been exposed to aminoglycans, but the timing of onset and severity of the disease is highly variable, even among carrier members of the same family.

Disease management

Hearing aids and therapy with speech therapists (educational programs for the hearing impaired) and cochlear implantation may be used. Electric acoustic stimulation may be used in cases where hearing has not been completely lost.

Genes analyzed

12S RNA (MTRNR1)

Bibliography

Chai Y, Sun L, Pang X, et al. Identification of both MT-RNR1 m.1555A>G and bi-allelic GJB2 mutations in probands with non-syndromic hearing loss. Int J Pediatr Otorhinolaryngol. 2014 Apr;78(4):614-7.

Lu J, Qian Y, Li Z, et al. Mitochondrial haplotypes may modulate the phenotypic manifestation of the deafness-associated 12S rRNA 1555A>G mutation. Mitochondrion. 2010 Jan;10(1):69-81.

Mohamed WKE, Arnoux M, Cardoso THS, et al. Mitochondrial mutations in non-syndromic hearing loss at UAE. Int J Pediatr Otorhinolaryngol. 2020 Nov;138:110286.

Mitochondrial mutations in hearing loss.

Usami SI, Nishio SY. Nonsyndromic Hearing Loss and Deafness, Mitochondrial. 2004 Oct 22 [updated 2018 Jun 14]. In: Adam MP, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2023.