Otolaryngology Research Increasingly Supports Genetic Screening to Evaluate Pediatric Hearing Loss

If you’re not offering a certain genetic test to determine the cause of sensorineural hearing loss (SNHL) in children, you should consider it, or refer your pediatric patients to specialists experienced with such diagnostics, according to a growing body of literature that underscores the value of genetic testing to determine the cause of SNHL in these patients.

The latest such study comes from the University of Miami. Writing in the November 2012 issue of Otolarynology—Head and Neck Surgery, researchers led by Xue Zhong Liu, MD, PhD, professor of otolaryngology, human genetics and pediatrics and director of research at the University of Miami Health System, showed that screening for common mutations in GJB2 and GB26 should be an early step in the diagnostic evaluation of pediatric hearing loss (Otolaryngol Head Neck Surg. 2012;147:932-936). These genes encode the proteins connexin 26 and 30, which form gap junctions, channels that allow potassium molecules to move between cells and enable normal hearing. Faulty connexin proteins disrupt the potassium recycling pathway and production of electrochemical signals, resulting in hearing loss.

About half of all congenital hearing loss is inherited, caused by mutations in more than 100 culprit genes but, in developed countries, 40 percent of hearing loss is caused by changes in GJB2. They are the most common cause in all ethnic groups, except those of African descent. GJB2, a relatively small and easy gene to test, can yield results that may spare some children from unnecessary, costly tests, some of which carry risks from radiation, noted the University of Miami researchers and other experts on genetic testing for hearing loss. Tests for these and other genes give some parents answers about causes of hearing loss, how it may progress, whether other medical problems may result and the chance of recurrence in siblings.

A Look at Real-Life Testing

Dr. Liu and his team wanted to determine the diagnostic yield of targeted genetic testing in both adult and pediatric populations with SNHL to develop effective testing strategies in their clinic. They screened blood from 221 adults and 163 pediatric patients with non-syndromic SNHL who visited the University of Miami Ear Institute between 2001 and 2010. The researchers screened for

mutations in GJB2 and GJB6, plus three mitochondrial DNA mutations that can cause deafness when patients with these genetic abnormalities take the antibiotic gentamicin. The researchers also collected patients’ family histories and audiometric testing data.