Prevalence of the A1555G MTDNA mutation in sporadic hearing-impaired patients without known history of aminoglycoside treatment

Abstract

IntroductionThe A1555G mitochondrial DNA (mtDNA) mutation is responsible for maternally inherited non-syndromic hearing loss that is increased by aminoglycoside exposure. The objective of this study was to ascertain the frequency of the A1555G mutation among patients without family history of hearing loss or known exposition to aminoglycosides. MethodsWe screened for the mtDNA A1555G mutation in Spanish patients with sporadic sensorineural hearing impairment without a known family history of hearing loss or aminoglycoside exposition seen at the ENT Department in Sierrallana Hospital (Torrelavega, Cantabria, Spain) over a four-year period. ResultsA total of 219 patients with bilateral hearing loss were screened. Two of them (0.9%) had the A1555G mitochondrial DNA mutation. Both patients had a moderate bilateral sensorineural hearing loss for low frequency, and moderate to severe loss for high-frequency. ConclusionsThe mtDNA A1555G mutation in patients with sensorineural hearing loss without family history of deafness or aminoglycoside ototoxicity is infrequent in our region. We should suspect this mutation in patients younger than 50 years old, with postlingual bilateral sensorineural hearing loss that is more pronounced at high frequency.