Maternally inherited hearing impairment in a family with the mitochondrialDNA A7445G mutation

Despite the increasing number of reports of families with hearing impairmen t and mitochondrial DNA (mtDNA) mutations, the frequency of these mutations as causes of non-syndromic sensorineural hearing impairment (NSSHI) remain s unknown. Mutations such as A1555G, A7445G and 7472insC have been found in several unrelated families implying they are more frequent than initially thought. We describe a family with NSSHI due to the presence of the homopla smic mtDNA A7445G mutation in the tRNASer((UCN)) gene. This is the fourth s uch family described with this mutation, all of different genetic backgroun ds. Our study also demonstrates the difficulties sometimes encountered in e stablishing mitochondrial inheritance of hearing impairment in some familie s.