THE GENETIC CONNECTION
Hayden Chen’s hearing loss may have come as a surprise to his family, especially because neither of his parents nor other family members had any hearing loss. However, the majority of hearing-impaired children are born to hearing parents. The genetic condition Hayden had is actually quite common. Connexin 26, a protein in the GJB2 gene, is responsible for allowing cells to communicate with each other. Without enough of this protein, the levels of potassium in the cochlea in the inner ear can become too high; this can lead to hearing loss. Mutations of Connexin 26 are the most common cause of hearing loss in newborns, resulting in as many as 50 percent of all congenital hearing loss. This is not the only genetic cause. According to the Centers for Disease Control and Prevention, 50 percent or more instances of hearing loss in newborns is genetic, while 25 percent or more hearing loss is environmental—or due to infections in the mother while the baby is in utero or complications after birth. The CDC states that about 70 percent of genetic mutations that cause hearing loss are what’s called non-syndromic, meaning they don’t come with
any other symptoms—like in Hayden’s case. The remaining 30 percent of genetic mutations are part of a syndrome that has other symptoms, like blindness, for example. The only way to determine if a child’s hearing loss is due to a genetic mutation is to do genetic testing early on. Rady ìðăÌīÐĊȸĮďååÐīĮĴìÐÅÐĊÐťĴ of genetic testing as part of its comprehensive hearing program. The tests must wait until the child is born—they cannot be done in utero. “Some parents are using 23andMe and other in-home genetic testing to test for genes they know to be responsible for hearing loss. If both parents are positive for certain genes, you know the baby will have a 25 percent chance of having hearing loss,” says Dr. Carvalho. Still, while genetic testing has come a long way, there’s still much more to discover. “We have genetic panels for 200 genes that we can test for hearing loss,” Dr. Carvalho adds. “But there are thousands more we just don’t know about yet.”
WINTER 2024 HEALTHY KIDS MAGAZINE 19
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