GJB2 and hearing loss disorder: In our cohort, the carrier rate of mono-allelic mutations in GJB2 (3.89% overall, 2.97% for c.235delC) is higher than that previously reported in the Chinese Han general population (2.45% overall, 1.78% for c.235delC) [32], suggesting that at least in some cases a second unidentified pathogenic mutation may act either in cis or in trans to the GJB2 mutation to lead to the hearing loss.