This significantly reduces the molecular genetic testing loads needed to reach a final genetic diagnosis through GJB2 testing alone.3 Although the proportion of nonsyndromic hearing loss and deafness 1 (DFNB1) among nonsyndromic sporadic or autosomal recessive severe to profound SNHL significantly varies, it still accounts for ∼15% of such subjects in Koreans, making GJB2 and solute carrier family 26, member 4 (SLC26A4) the most frequent causative genes of SNHL.3–7 However, it is not always straightforward to diagnose DFNB1 in subjects carrying GJB2 mutations. The gene discussed is GJB2; the disease is autosomal recessive nonsyndromic hearing loss 1A.