Although all cases of hereditary hearing loss are very similar in terms of the symptom of hearing loss, the clinical characteristics, such as the severity and progression of the hearing loss, whether it fluctuates, and accompanying symptoms, vary slightly depending on the causative gene and type of pathogenic variant. Therefore, by identifying the causative gene through genetic testing, it is possible to classify subtypes and identify the most appropriate medical treatment for each patient based on the clinical characteristics of each causative gene. Molecular diagnosis (genetic testing) is now crucial for facilitating an accurate diagnosis, predicting the severity and progression of hearing loss, estimating associated abnormalities, determining suitable therapeutic interventions, preventing hearing loss, and enhancing genetic counseling.