background: autosomal recessive non-syndromic hearing loss (arnshl) is the most common hereditary form of deafness, and exhibits a great deal of genetic heterogeneity. so far, more than seventy various dfnb loci have been mapped for arnshl by linkage analysis. the contribution of three common dfnb loci including dfnb3, dfnb9, dfnb21 and gap junction beta-2 (gjb2) gene mutations in arnshl was in...