Mitochondrial nonsyndromic sensorineural hearing loss. A clinical, audiological and pathological study from Italy and revision of the literature

International audienceOver the last decade a number of distinct mutations in the mitochondrial DNA (mtDNA) have been found to be associated with both syndromic and nonsyndromic forms of hearing impairment. Their real incidence as a cause of deafness is yet poorly understood and generally underestimated. Among the known mtDNA mutations, the A1555G in the 12S gene has been identified to be one of the most common genetic cause of deafness, and it has been described both associated to nonsyndromic progressive sensoryneural hearing loss (SNHL) and to aminoglycoside induced SNHL. In this study, we have investigated the presence of mtDNA alterations in patients affected by idiopathic nonsyndromic SNHL, both familiar and sporadic, in order to evaluate the frequency of mtDNA alterations as a cause of deafness and to describe the audiological manifestations of mitochondrial nonsyndromic SNHL. Consistently with literature data, we found the A1555G mutation to be responsible of a relevant percentage (5,4%) of cases affected with isolated idiopathic sensorineural hearing impairment