In the second part, we supposed that a number of patients are only carriers of one heterozygous pathogenic GJB2 variant by chance, and that the cause of their hearing loss is on a gene other than the GJB2. Therefore, we performed whole exome sequencing (WES) of 49 patients, 17 of whom we examined in both parts of the project. The gene discussed is GJB2; the disease is hearing loss disorder.