The CDH23 gene helps build tiny links that let inner ear cells detect sound and head movement, and it also supports parts of the eye. When this gene does not work properly, people may have hearing loss from birth, balance problems, and sometimes vision loss over time. Differences in this gene can help explain why people develop either isolated hearing loss or Usher syndrome, a condition that affects hearing, balance, and eyesight.
What is a gene?
Genes are stretches of DNA that carry instructions your cells use to make molecules or regulate processes in the body. Some genes provide the information needed to produce proteins, the cell parts that do much of the work. Others mainly help control when certain processes happen, where they happen, and how active they are. Together, genes affect how the body develops and functions, and they can influence how you respond to food, stress, or medications. More information on this topic is available in the LearnHub.
Overview
CDH23Gene function
What if the gene works
The CDH23 gene helps inner ear cells detect sound and balance signals. Its protein supports tiny links on these cells and also helps light sensing cells in the retina.
Risk
What if the gene does not work
Variants in the CDH23 gene can cause hearing loss that ranges from milder to profound. More disruptive variants often lead to Usher syndrome type 1D, with early hearing loss, balance problems, and later vision loss from retinitis pigmentosa.
Treatment
What does that mean for your treatment
No CDH23-specific treatment or drug choice is currently established in clinical guidelines for pathogenic variants in the CDH23 gene. Care currently follows standard hearing and vision management, while the CDH23 gene is being studied in early gene therapy and other experimental approaches for inherited hearing loss and Usher syndrome.
Conditions associated with CDH23
Gene function
What if the gene works
Hearing and balance depend on tiny inner ear cells that bend with sound and movement. The CDH23 gene helps these cells stay connected in a way that lets them turn motion into nerve signals. Understanding what the CDH23 gene does helps explain how the ear detects a doorbell ring or helps you stay steady when you turn your head.
The CDH23 gene makes a protein that helps certain sensory cells hold onto nearby structures. This is especially important in the inner ear, where tiny hair-like parts need stable, flexible connections.
In hearing cells, CDH23 helps form tip links, which are tiny links between hair-like projections. When sound bends these projections, those links help start the electrical signal that carries sound information.
Similar links in balance cells help detect head movement and position. This lets the inner ear convert everyday motion, like walking or turning, into signals your brain can use to stay oriented.
CDH23 supports the orderly arrangement of the inner ear’s hair-like projections. Keeping this structure organized helps these cells respond to movement in a controlled, reliable way.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. These differences are common and help shape normal human diversity, including differences in appearance, metabolism, or the way the body responds to environmental influences. Many variants do not have any noticeable effect and simply reflect natural genetic variation. In some situations, though, a variant can change how a gene works more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the CDH23 gene can change the cadherin-23 protein so it folds poorly, is unstable, or cannot form the tiny links that help inner ear cells turn vibration into nerve signals. More disruptive variants may greatly reduce or stop the protein, while milder variants often leave some activity. This helps explain why some CDH23 gene variants linked to hearing loss cause earlier, broader features such as Usher syndrome, while others mainly cause isolated hearing loss.
How variants are linked to conditions
Pathogenic variants in the CDH23 gene can cause inherited hearing conditions, most often nonsyndromic hearing loss and Usher syndrome type 1D. In people with CDH23 gene variants linked to hearing loss and Usher syndrome, some have hearing loss alone, while others also develop vision loss from retinitis pigmentosa and may have balance problems. The pattern depends on the specific variants a person carries.
A variant is not necessarily a diagnosis
Variants in genes are a routine part of human biology and are widespread in the general population. Most do not directly affect health and instead reflect normal human variation. For many genes, carrying a variant associated with a condition suggests a possible link rather than a confirmed diagnosis, especially when several genes and environmental factors are involved. In contrast, a single well-characterized variant in a specific gene can sometimes be enough to establish a diagnosis.
Are there things that can increase or change my risk?
For CDH23-related conditions, the main risk factor is genetic: inheriting harmful changes in both copies of the CDH23 gene. There is not enough evidence to say that lifestyle or environmental changes lower the chance of developing a CDH23-related condition, although loud noise and some medicines can still worsen hearing over time.
Inheritance of CDH23 variants
CDH23-related conditions are usually inherited in an autosomal recessive pattern. This means a child typically inherits one CDH23 gene variant from each parent, and parents who carry one variant usually do not have the condition themselves. For families asking how CDH23 gene variants are inherited, each pregnancy between two carriers has a 25% chance of resulting in a child with the condition, a 50% chance of having a child who is a carrier, and a 25% chance of having a child with no inherited variant in the CDH23 gene. This pattern is the same for the well-known hearing loss and Usher syndrome forms linked to the CDH23 gene.
What does my CDH23 result mean for my family?
For families with a disease-causing change in the CDH23 gene, the main pattern is recessive, which means close relatives may also be carriers even if they do not have hearing or vision problems. Brothers and sisters could be affected or be carriers, so the result can matter for siblings as well as future children in the family. The family meaning depends on whether one changed copy or two were found in the person tested.
Genetic information
Genetic testing
How you find out about variants
CDH23 genetic testing uses a blood or saliva sample to read the CDH23 gene and look for variants linked to inherited hearing loss and some forms of Usher syndrome. Results can show whether a person carries a variant, has two disease causing variants that may explain symptoms, or has no clearly relevant change.
When should I consider getting a genetic test?
Genetic testing may be worth considering if hearing loss starts early in life, especially if it runs in the family or comes with balance problems. Changes in the CDH23 gene can cause some inherited forms of deafness and Usher syndrome, which can also affect vision over time. Testing can clarify the cause and guide follow-up.
A genetic result is only one part of your health story
A genetic result can be informative, but what it can tell you varies with the condition and the kind of variant identified. How the body functions over time is also shaped by many factors, including lifestyle, environment, age, and medical history. In some conditions, particularly those influenced by many genes, genetic information provides context rather than certainty and is most useful when considered with other parts of care. In other situations, a genetic result can offer a clear answer. For medication response, genetic results can also help put individual experiences in context.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how your body handles certain medicines. This helps explain why the same treatment works well for one person, seems weaker for another, or causes more side effects in someone else. Some gene differences influence how quickly a drug is broken down, moved through the body, or reaches its target. These differences are common and can shape both how well a medicine works and how sensitive a person may be to it.
What is Pharmacogenetics?
Pharmacogenetics looks at how genetic differences can shape a person’s response to medications. It examines links between genes and drugs to help explain why the same treatment may work differently from one person to another. For many medicines, genes can affect either how strongly a drug works or how the body handles it. This information can support treatment decisions that are both more informed and more individualized. More detail on this topic is available in the LearnHub.
Drugs influenced by the CDH23 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in how people respond to medicines. Questions about side effects, new symptoms, or whether a treatment is right for you are best discussed with your doctor or pharmacist.
History
The CDH23 gene entered medical genetics through studies of inherited hearing loss and Usher syndrome, a condition that affects hearing, balance, and vision. In the late 1990s and early 2000s, researchers linked variants in this gene to Usher syndrome type 1D and later to some forms of nonsyndromic deafness. Initially understood only through visible traits, later recognized as tied to a specific gene, these findings helped connect family patterns of deafness with a clear genetic cause. From these first observations, research expanded steadily. Work on CDH23 also became important in hearing science because it helped explain how the inner ear’s sound sensing structures are built and maintained. Over time, this made CDH23 a well established part of both deafness research and sensory genetics.