MCAT and hearing loss disorder: Background Genetic mutations in <i>GJB2</i> and <i>GJB3</i> are primarily associated with non-syndromic sensorineural congenital hearing loss (HL), whereas mutations in <i>SLC26A4</i> and MT-RNR1 are linked to syndromic or mixed forms of sensorineural HL and are among the most commonly investigated hearing loss-associated genes.