Natural History in Children up to 16 Years With Mild to Profound Hearing Loss Due to Mutations in GJB2 / OTOF Genes

Main Inclusion Criteria: Participants meeting all the following main inclusion criteria will be eligible to participate in the study: * Aged ≤ 16 years on the date of signed informed consent for cohort 1 and ≤ 10 years for cohort 2; * With a diagnosis of non-syndromic, bilateral, mild to profound, sensorineural hearing loss (according to the American Speech Language-Hearing Association); * With documented genotyping results showing mutation(s) in GJB2 or OTOF genes; * Written informed consent as required by local regulations. * Either without Cochlear Implant, or with unilateral or bilateral Cochlear Implant(s) Exclusion Criteria: Participants presenting with any of the following main exclusion criteria will not be included in the study * Other type of deafness, such as unilateral deafness, persistent conductive deafness, malformation syndrome, syndromic deafness, known familial deafness linked to mutations in other genes than OTOF or GJB2; * Documented genotyping results showing pathogenic mutation(s) in other gene(s) than GJB2 or OTOF genes in the tested panel; * Unable and/or unwilling to comply with all the protocol requirements and/or study procedures.