Deafness genes.

The pathophysiology of sensorineural hearing impairment, which is a common clinical disorder, remains yet to be determined. For prelingual hearing loss, epidemiological data show that 1 neonate in 1,000 is born with severe to profound hearing loss, and in half of that number the loss is inherited. Some genes responsible for sensorineural hearing impairment have been cloned during the last several years, and the underlying mechanisms causing hearing impairment have begun to be clarified with the advent of recent developments in molecular genetics. Cases of non-syndromic deafness are classified by the mode of inheritance (DFNA, dominant; DFNB, recessive; DFN, X-linked), with the loci being numbered in the order of discovery. To date, 31 autosomal dominant, 28 autosomal recessive, and 6 X-linked non-syndromic sensorineural hearing impairment loci have been mapped, and 17genes have been cloned (Hereditary Hearing Loss Homepage, http://danallab-www.uia.ac.be.dnalab/hhh/). We have identified mutations in four of those 17 deafness genes in Japanese families. Clinical and genetic findings of the above disorders are reviewed.