GJB2 and autosomal dominant nonsyndromic hearing loss: Pathogenic missense variants in the GJB2 gene, resulting in amino acid substitutions, lead to a variety of clinical outcomes, including the most common non-syndromic autosomal recessive deafness (DFNB1A), autosomal dominant deafness (DFNA3A), as well as syndromic forms combining hearing loss and skin disorders.