GJB2 and hearing loss disorder: In Snoeckx’s multicenter study [16], they performed cross-sectional analyses of GJB2 genotype and audiometric data from 1,531 patients with mild to profound nonsydromic hearing impairment, found the wide phenotypic variability of DFNB1 deafness, even among subjects homozygous for the same mutation, and it suggested that this variability might reflect the effect of modifier gene and/or environmental factors that lead to incomplete penetrance and variable expression.