GJB2 and hearing loss disorder: Despite the wide genetic heterogeneity of hearing impairment, the most commonly mutated genes in severe to profound autosomal recessive non-syndromic hearing loss (ARNSHL) are GJB2 and GJB6 (encoding connexin-26 and 30, respectively), accounting for nearly 50% of the cases in most populations around the Mediterranean Sea [6,7,8,9,10,11].