The role of genetics in hearing loss is significant, with many types of hearing disorders having a genetic basis. Genetic mutations can affect the inner ear’s development or damage its delicate structures, leading to inherited hearing loss. Dominant pattern inheritance occurs when an affected person has a 50% chance of passing the mutation to their offspring. Recessive pattern inheritance occurs when both parents carry a copy of the mutation, causing their children to be affected. Understanding the genetic basis of hearing loss can help individuals and their families to better comprehend the condition and make informed decisions regarding management and treatment options.
Dominant and Recessive Hearing Loss
Researchers use the term “dominant hearing loss” to describe a situation where one copy of a mutated gene is enough to cause hearing impairment. The mutation can be inherited from either parent or appear for the first time in a family without a history of deafness. Dominant genes have a 50% chance of passing from parent to child and can have different effects on different individuals, causing varying degrees of hearing loss or even skipping some generations.
Recessive hearing loss occurs when two copies of a mutated gene are required to cause hearing impairment. Carriers usually inherit the mutation from both parents who are carriers. However, mutations can also occur spontaneously during development. Compared to dominant genes, the chance of passing on a recessive gene is only 25%. However, their effects are consistent between patients.
How Do Genetics Cause Hearing Loss?
The way genes cause hearing loss depends on the specific mutation. For instance, GJB2 is an example of a gene that causes non-syndromic recessive hearing loss. It encodes a protein called connexin 26 which plays a vital role in the functioning of the cochlea (the part of the ear that converts sound waves into nerve signals). Mutations in this gene cause connexin 26 to function differently, typically leading to blindness and deafness at birth or early childhood.
Other mutations affect the mitochondria in ear cells by disturbing energy production. Patients with these genes develop sensorineural hearing loss later in life due to exposure to certain antibiotics.
In total, more than 100 gene mutations are directly associated with hearing loss. Problems with connexin encoding are the most common, but many other rarer disorders require genetic testing to diagnose. Hundreds more cause other conditions that may also lead to hearing loss.
With that said, not all genes automatically cause hearing loss. Many mutations simply increase the risk of hearing loss developing as a person gets older. Environment often interacts with these genes to determine when and how hearing loss will occur. This process is similar to other degenerative diseases, such as cancer and heart disease, where genes may increase a person’s risk, but they don’t always guarantee illness will occur.
Genetic Testing and Counseling for Genetic Hearing Loss
The vast majority of hearing loss is age and lifestyle-related. However, some cases are genetic.
In these cases, genetic testing and counseling can help identify if someone has a genetic cause for their hearing loss or is at risk of passing it on to their children. These tests typically analyze DNA samples from blood and sputum and then use sequencing techniques, like microarray analysis, to look for telltale mutations.
Genetic testing is highly comprehensive and searches for hundreds of genes associated with hearing loss. Laboratory technicians and medical professionals conduct detailed analyses and then tell patients what each mutation means and whether it is the likely cause of symptoms. Note that some mutations only increase the risk of developing hearing loss. They do not guarantee that you have the condition.
Genetic counseling provides information and support about genetics and deafness by trained professionals such as geneticists. It is a specialized field concentrating on helping people manage the gene-related factors associated with a particular health condition.
The first step involves an evaluation of your medical history, family history, and current symptoms. Once counselors receive test results, they may recommend additional testing based on the findings. Following diagnosis, genetic counselors work with individuals and families to diagnose the condition. At this stage, they may recommend treatments, such as hearing aids and cochlear implants.
Genetic counselors may also begin discussions involving family planning and the risks of passing hearing loss onto future generations. This approach lets parents make informed decisions on reproductive options.
Getting to the Bottom of Hearing Loss
If you’d like to learn more about genetic hearing loss or want to schedule a hearing evaluation, get in touch with The Hearing Center at York ENT. Our team of trained audiologists offers comprehensive diagnostic services, showing you what’s causing the hearing loss and how to treat it. Simply call (717) 850-9269 to schedule an appointment today.
