The purpose of this study is to follow the natural history of non-syndromic hearing loss caused by mutations in two genes (GJB2 or OTOF) in children up to 16 years of age.

The study aims to:

• better describe the prevalence of cases of DFNB1A and DFNB9, including the type of mutations, and to assess the clinical course of the disease in children up to 16 years of age who have a mild to profound deafness.
• better understand the audiological and genetic characteristics of the participants with congenital versus evolutive DFNB1A and DFNB9 deafness.

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.

Male and female participants aged ≤ 16 years at selection, with a diagnosis of bilateral, moderate to profound, sensorineural, non-syndromic hearing loss, with genotyping results showing mutation(s) in GJB2 or OTOF genes, with and without cochlear implant (CI).