A second kindred linked to DFNA20 (17q25.3) reduces the genetic interval

A family ascertained in the United States displays significant evidence of linkage to 17q25.3 (maximum two-point LOD score 6.32). The non-syndromic autosomal-dominant hearing-loss loci DFNA20 and DFNA26 map to this region. The 3-unit support interval and haplotype for this USA kindred falls within the interval for DFNA20 and DFNA26 and reduces the region to 6.05 cM, according to the deCode genetic map. The same gene is probably responsible for both DFNA20/DFNA26. In addition, the USH1G locus maps to this region and could be an allelic variant of the gene responsible for DFNA20/DFNA26. Clinical data is presented for this kindred, where hearing-impaired family members present with sloping audiograms with mid- and high-frequency hearing loss, which progresses to hearing loss that affects all frequencies. The mean age of onset of hearing impairment is 13.2 years of age (standard deviation: 4.6 years).