Importance of Genetic Testing for Late-onset Hearing Loss

Hereditary hearing loss accounts for about one-third of all cases of late-onset hearing loss of unknown etiology that manifests before the age of 40 years. A representative type of late-onset hereditary hearing loss is early-onset bilateral sensorineural hearing loss. So far, 11 genes (ACTG1, CDH23, COCH, KCNQ4, TECTA, TMPRSS3, WFS1, EYA4, MYO6, MYO15A and POU4F3 genes) have been implicated as causative genes for early-onset bilateral sensorineural hearing loss. Late-onset hearing loss is often identified during medical checkups at schools or companies, and therefore, the patients are more likely to visit ENT practitioners than core hospitals including university hospitals. ENT physicians examining these patients are often not necessarily familiar with audiology and genetic medicine and may fail to refer them for genetic testing. The first step in a patient with late-onset hearing loss of unknown etiology is to have a high index of suspicion for genetic involvement. The next step is to obtain a detailed medical history to determine the time of onset of hearing loss, the course of progression of the hearing loss, and the presence of any family history of hearing loss. Improved awareness among otolaryngologists about the possibility of genetic involvement in patients who present to them with late-onset hearing loss will be expected to improve the referral rate of such patients to appropriate medical institutions and improve the rate of diagnosis of late-onset hereditary hearing loss.