Abstract
Approximately half of the prelingual deafness is considered to be associated with hereditary hearing impairment (HHI), most commonly presenting as autosomal recessive non-syndromic deafness (ARNSD). The first locus of the ARNSD, DFNB1, was localized to chromosome 13q11, and the mutations in Gap junction beta 2 gene (GJB2) is now reported to be the cause of the deafness with DFNB1 locus. Connexin 26, which is the protein product of GJB2, is the subunits that form gap junctions and play an important role in intercellular communication, especially in the view from potassium ion cycling in cochlea. Clinically, GJB2 mutations were found to be the cause of approximately half of severe-to-profound ARNSD in many countries around the world. Most frequent mutations found in Japanese population is 235delc, while 35delG predominates in the many other populations. Babies with GJB2-ralated deafness have non-syndromic hearing loss typically in the severe-to-profound range, althogh moderate losses also can be identified. Higher speech performance after cochlear implant was reported in the cases with GJB2-related deafness, comparing with their GJB2-unrelated peers with cochlear implant. Although genetic testing can be applied to identify the mutations of GJB2; ethical problems should further be discussed beforehand.
