Hearing loss can be inherited, and genes are a leading cause of permanent hearing loss that starts in babies and young children. That doesn’t mean anyone else in the family has it: the most common forms are carried silently by parents who hear normally. The gradual hearing loss many people develop with age is inherited too, but more loosely, spread across many genes and shaped by noise and general health. Knowing the genetic cause has also become more useful, because the first gene treatments have now restored hearing in some children.
How Much Hearing Loss Runs in Families
About half of permanent hearing loss present at birth has a genetic cause. Genetic testing finds the cause in roughly 43 to 47 percent of children with sensorineural hearing loss, the inner-ear kind.1PubMed. Genetic testing for pediatric sensorineural hearing loss in the era of gene therapy2PubMed Central. Diagnostic Yield in Childhood-Onset Hearing Loss: A Meta-Analysis and Systematic Review The odds shift with the child’s features, though, and the chance of finding a genetic cause ranges from about 10 to 60 percent.3PubMed. Genetic testing for pediatric sensorineural hearing loss in the era of gene therapy
Whether one ear or both are affected is a big part of that. Loss in both ears from birth points more strongly toward genes. Loss in one ear is much less often genetic: testing finds a cause in only about 5 percent of those children.4PubMed Central. Diagnostic Yield in Childhood-Onset Hearing Loss: A Meta-Analysis and Systematic Review It more often comes from infections such as cytomegalovirus or from structural differences in the inner ear.
Two words get used loosely here. Genetic means a gene change causes the hearing loss. Hereditary means it was passed down from a parent. A child can have genetic hearing loss inherited from two hearing parents, and occasionally a gene change appears in the child for the first time. About 7 in 10 genetic hearing losses affect only hearing, while about 3 in 10 come with other features such as eye or skin changes.
A failed newborn screen is not a diagnosis of any cause. It only says the baby needs a full hearing evaluation, not whether hearing loss is present or how severe it is. Fluid or debris in a newborn’s ear can cause a failed screen that clears up on retesting, so follow-up testing comes before any conclusions about genes. Once permanent loss is confirmed, finding the cause is a separate step with a history, an exam and sometimes lab or genetic tests.
How Hearing Loss Is Passed Down
About 75 to 80 percent of inherited hearing loss that comes without other features is recessive, meaning the child needs a changed copy of the gene from both parents. Parents who each carry one copy usually hear normally and often have no family history at all. Each child of two carrier parents has a 1 in 4 chance of the hearing loss.
That 1 in 4 applies to every pregnancy separately, not as a quota spread across children. Two carrier parents can have several hearing children, or several deaf children. Hearing siblings may be carriers themselves, which matters when they plan families.
About 20 percent is dominant, where one changed copy from one parent is enough, giving each child a 1 in 2 chance. Dominant hearing loss tends to be milder than recessive loss.5PubMed. Nonsyndromic hearing loss: an analysis of audiograms It also varies more between relatives, so one family member may be far more affected than another.6PubMed. Nonsyndromic hearing loss: an analysis of audiograms A small share is passed through the X chromosome, mostly affecting boys, or through mitochondria, which come only from mothers.
Your own family tree can offer clues. Hearing loss in a parent and grandparent, in a straight line down the generations, suggests a dominant pattern. Hearing loss only in siblings whose parents hear normally suggests a recessive one. Loss that passes only through the mothers’ side can hint at a mitochondrial cause, though that is rare. Count relatives with mild or late-onset loss too, since dominant forms can be mild and easy to overlook.
The Most Common Gene, Connexin 26
Changes in GJB2, the gene that makes a protein called connexin 26, cause up to half of inherited severe-to-profound hearing loss present before a child learns to speak.7PubMed. Connexin 26 as a cause of hereditary hearing loss More than 340 different changes in this gene are known.8PubMed Central. Pathological mechanisms of connexin26-related hearing loss: Potassium recycling, ATP-calcium signaling, or energy supply? Most cause recessive hearing loss, so it usually arises in children of hearing carrier parents.9PubMed Central. Pathological mechanisms of connexin26-related hearing loss: Potassium recycling, ATP-calcium signaling, or energy supply? Connexin 26 forms channels between inner-ear cells that recycle potassium, keeping the fluid balance the ear needs to hear.10PubMed. Connexin 26 as a cause of hereditary hearing loss11PubMed Central. Pathological mechanisms of connexin26-related hearing loss: Potassium recycling, ATP-calcium signaling, or energy supply?
Because it is the most common single cause, many testing programs check the connexin 26 gene early, and a positive result can end a long search. It usually affects only hearing, so a result often reassures parents that other health problems aren’t expected. Children with it generally do well with cochlear implants because the hearing nerve works normally. The loss can range from mild to profound, even among children with the same gene change, so the result alone doesn’t predict severity. Both parents are usually carriers, and they can confirm this with their own tests.
Hearing Loss That Comes With Other Signs
Hearing loss that comes with other features is called syndromic hearing loss. Usher syndrome is the most common genetic cause of combined hearing and vision loss.12PubMed Central. Usher Syndrome It is recessive and causes retinitis pigmentosa, a gradual loss of vision, and sometimes balance problems.13Journal of Human Genetics. Is Bad Hearing Hereditary? The Genetics of Hearing Loss Its three types differ in how severe the hearing loss is, whether balance is affected, and when vision loss starts.14Journal of Human Genetics. Is Bad Hearing Hereditary? The Genetics of Hearing Loss
A deaf child who is late to sit or walk, or seems unusually clumsy, may have the balance problems linked to Usher type 1. Trouble seeing in dim light or at night is often the first vision sign, and it can appear in childhood or the teen years. Because vision changes come on slowly, a regular eye exam by a doctor who knows about Usher can catch them before a family notices.
Changes in the SLC26A4 gene cause Pendred syndrome, the most common recessive syndrome with deafness.15PubMed Central. Mutations of KCNJ10 together with mutations of SLC26A4 cause digenic nonsyndromic hearing loss associated with enlarged vestibular aqueduct syndrome A swelling in the neck from an enlarged thyroid can appear, often later in childhood. The same gene can cause hearing loss with an enlarged vestibular aqueduct, a widened canal in the inner ear seen on scans, without the thyroid signs.16PubMed. Association of SLC26A4 mutations with clinical features and thyroid function in deaf infants with enlarged vestibular aqueduct17PubMed Central. Mutations of KCNJ10 together with mutations of SLC26A4 cause digenic nonsyndromic hearing loss associated with enlarged vestibular aqueduct syndrome
An enlarged vestibular aqueduct changes daily advice. Hearing can drop in steps after head bumps, so doctors often advise avoiding contact sports and head injury.
Waardenburg syndrome pairs hearing loss with pigment changes such as a white forelock, pale skin patches, vivid blue eyes or two different eye colors.18PubMed. Review and update of mutations causing Waardenburg syndrome Type 2 is dominant, so it usually shows in a parent.19PubMed. Waardenburg syndrome type 2 caused by mutations in the human microphthalmia (MITF) gene A white streak of hair or different-colored eyes in the child or a parent is worth mentioning to the care team. An eye exam, thyroid check or scan may be suggested depending on the suspected syndrome.
Genetic Testing for Hearing Loss
Testing for children uses either a gene panel, a set of known hearing genes, or exome sequencing, which reads nearly all genes. Both find a cause about equally often.20PubMed Central. Diagnostic Yield in Childhood-Onset Hearing Loss: A Meta-Analysis and Systematic Review In children whose hearing loss is the only one in the family, testing still finds a cause in about 38 percent.21PubMed Central. Diagnostic Yield in Childhood-Onset Hearing Loss: A Meta-Analysis and Systematic Review In one large study, exome testing found a cause in about 41 percent with loss in both ears and 18 percent with loss in one ear.22PubMed. Exome Sequencing Expands the Genetic Diagnostic Spectrum for Pediatric Hearing Loss The tradeoff is that about 1 in 20 families learned of an unrelated health finding they had not been looking for.23PubMed. Exome Sequencing Expands the Genetic Diagnostic Spectrum for Pediatric Hearing Loss
The process is simple. It usually needs a blood sample or cheek swab from the child, and sometimes from the parents to help interpret the result. Results often take several weeks, so expect a wait rather than an answer at the appointment. A genetic counselor can explain what the result means for the child, for siblings and for future pregnancies. Before testing, decide whether you want to hear about unrelated findings.
A genetic diagnosis now shapes care, including whether a child may qualify for gene therapy.24PubMed. Genetic testing for pediatric sensorineural hearing loss in the era of gene therapy Ask your child’s audiologist or ear doctor for a genetics referral soon after diagnosis.
If no cause is found, that doesn’t prove the loss isn’t genetic, because some genes are still undiscovered. Testing can be repeated years later as more are identified. Other causes, such as cytomegalovirus infection, may be checked separately.
Genes That Make Ears Vulnerable to Certain Antibiotics
Aminoglycosides, a group of strong antibiotics including gentamicin and amikacin, can damage hearing in anyone at high doses. But people carrying changes in a mitochondrial gene, especially one called m.1555A>G, can lose hearing even from normal doses.25PubMed Central. Mitochondrial DNA mutations associated with aminoglycoside induced ototoxicity26Egyptian Journal of Medical Human Genetics. Aminoglycoside induced ototoxicity associated with mitochondrial DNA mutations These changes make the body’s own energy-making machinery resemble bacteria, so the antibiotic attacks it.27PubMed Central. Mitochondrial DNA mutations associated with aminoglycoside induced ototoxicity How much hearing is lost varies widely even within a family carrying the change.28PubMed Central. Mitochondrial DNA mutations associated with aminoglycoside induced ototoxicity
Because mitochondria come only from the mother, the risk passes down the maternal line, to all of a carrier mother’s children. A father with the change does not pass it on. Rapid hearing loss after a hospital antibiotic course in a relative is a clue worth mentioning to doctors. Fast genetic tests for this change exist, and some hospitals check before giving these drugs, particularly in newborn units. This is a special concern for premature babies, who are often given aminoglycosides in neonatal intensive care.29PubMed. The prevalence of mitochondrial mutations associated with aminoglycoside-induced sensorineural hearing loss in an NICU population
Age-Related and Noise-Related Hearing Loss
Age-related hearing loss depends on many genes, each adding a small amount of risk.30PubMed. The genetic landscape of age-related hearing loss Large studies have found dozens of gene regions tied to adult hearing difficulty, but each has only a small effect on its own.31PubMed Central. Presbycusis Across the Lifespan: Genetic, Molecular, and Multi-Omics Contributions So no single test can tell an adult whether they will lose hearing with age.
Some people’s ears are also more easily damaged by noise. Genes involved in handling stress on cells, potassium flow and hair-cell structure affect how easily noise harms hearing.32PubMed Central. The Role of Genetic Variants in the Susceptibility of Noise-Induced Hearing Loss If your parents lost hearing early, protect your own ears from loud noise with earplugs or earmuffs.
A baseline hearing test in middle age lets later changes be spotted early by comparison. Hearing aids work the same way whether the cause is genetic or not.
Gene Therapy for Inherited Deafness
The otoferlin gene makes a protein that inner-ear hair cells need to pass sound signals to the hearing nerve.33PubMed. Otoferlin, defective in a human deafness form, is essential for exocytosis at the auditory ribbon synapse Children missing it have intact hair cells that can’t send signals, which gene therapy aims to fix by delivering a working copy. In one trial, 9 of 12 children improved after a single treatment, and 3 reached normal average hearing.34PubMed. DB-OTO Gene Therapy for Inherited Deafness In another, children treated in both ears all regained hearing, with no serious side effects.35PubMed Central. Bilateral gene therapy in children with autosomal recessive deafness 9: single-arm trial results
Other forms are harder. Unlike birds and fish, mammals can’t regrow lost hair cells.36PubMed Central. Feathers and Fins: Non-mammalian models for hair cell regeneration Forms that destroy hair cells, such as many syndromes, are therefore harder to treat with a replacement gene. Researchers are studying how to coax supporting cells in the ear to turn into new hair cells.37PubMed Central. Epigenetic Mechanisms of Inner Ear Development
For families now, these treatments are still in trials and are not routine care. Only a genetic test can show whether a child has the otoferlin form. Cochlear implants and hearing aids remain the standard, effective treatment for most children. If testing finds a treatable gene, a genetics clinic can help a family ask about trials.
Many Deaf people see deafness as a culture with its own language rather than a disability. Many welcome testing to learn a cause but are wary of prenatal testing. Good genetic counseling respects these values and the family’s own choices.