Mitochondrial Hearing Loss Mutations among Finnish Preterm and Term-Born Infants

Mitochondrial ribosomal 12S subunit gene (MTRNR1) is a hot spot for hearing loss mutations. Mutations such as m.1555A>G, m.1494C>T and m.1095C>T, cause sensitivity to aminoglycosides. Aminoglycoside treatment induces permanent hearing loss or deafness in the carriers and should therefore be avoided. The prevalence of these sensitivity mutations varies in different countries and populations. Over 90% of preterm children need aminoglycoside treatment during their first weeks of life. Infants who carry a mitochondrial sensitivity mutation can develop a life-long sensorineural hearing impairment as a side-effect of aminoglycoside treatment. Total of 813 Finnish preterm (born G, m.1494T>C and m.1095C>T mutations. The population prevalence of m.1555A>G was determined to be 0.12% in Finland. M.1494C>T and m.1095C>T mutations were absent. Out of the 813 infants, a term-born infant was found to harbor m.1555A>G at 81% heteroplasmy, while his mother’s heteroplasmy was 68%. Both had normal hearing and had not received aminoglycosides. Mothers with a family history of hearing loss who are at risk of preterm labor would benefit from antenatal genotyping of m.1555A>G mutation. The prevalence of m.1555A>G in Finns was close to other European countries. M.1494C>T and m.1095C>T mutations either do not occur in the Finnish population or they are very rare. This study highlights the importance of population-specific genotyping of MTRNR1 aminoglycoside sensitivity mutations, especially in countries with liberal aminoglycoside use.