Why does my child have hearing loss?
Hearing science professionals estimate that 1 to 3 babies per 1,000 are born with some degree of hearing loss.
The cause of your child's hearing loss will be one of the following:
- Genetic – 50% of childhood hearing loss has a genetic component.
- Non-genetic due to illness or trauma – 25% of cases
- Unknown – 25% of cases
Genetics of Hearing Loss | CDC
What are
genes?
- Genes are the hereditary units that determine body structure, function, and development.
- Half our genes come from our mother and the other half come from our father. We pass half our genes to each child.
In approximately 70% of
genetic hearing loss, the cause is
autosomal recessive.
Autosomal recessive inheritance means:
- A person needs a pair of non-working genes to cause autosomal recessive hearing loss.
- A parent carries one of the recessive genes responsible for deafness while the other copy of that same gene is working.
- Since each parent typically has only one recessive gene causing hearing loss, both parents usually have typical hearing.
- If each parent passed one copy of the
altered recessive gene, then the child would receive two recessive genes causing hearing loss (one from each parent) and
would have hearing loss.
- Two carrier parents have a 25% chance in each pregnancy to have a child with hearing loss.
- There are many different genes in many different locations that may cause recessive genetic hearing loss.
Autosomal Recessive Nonsyndromic Hearing Loss Genes | Hereditary Hearing Loss Homepage and many syndromic forms.
Autosomal dominant inheritance (approximately 15% of cases) means:
- Only one copy of the
altered gene is needed to cause hearing loss. Therefore, the parent with the altered gene will typically have some degree of hearing loss.
- The parent with the dominant gene
has a 50% chance to pass the hearing loss gene to each child.
- Sometimes a parent has the dominant gene for hearing loss yet has normal hearing (reduced penetrance).
- A new dominant gene causing hearing loss can arise in a family for the first time (de novo).
- There are many different genes in many different locations that may cause dominant genetic hearing loss.
Autosomal Dominant Nonsyndromic Hearing Loss Genes | Hereditary Hearing Loss Homepage and many syndromic forms.
X-linked Inheritance (1-2%)
Mitochondrial Inheritance (1%)
- Mitochondrial forms of hearing loss are due to pathogenic variants in
mitochondrial genes.
- There are isolated forms and syndromic forms
here.
- A form of mitochondrial hearing loss is induced with some types of antibiotic use.
Mito University | UMDF
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Will my child have other medical issues?
- Hearing loss occurring by itself is called isolated or
non-syndromic; and hearing loss with other medical issues is called
syndromic.
- Approximately 70% of childhood hearing loss is isolated.
- Sometimes hearing loss appears to be isolated but the other symptoms may not be apparent at a young age.
What is the likelihood that hearing loss will happen again with other children in my family?
If the cause of your child's hearing loss is an
autosomal
recessive condition, then the likelihood that this will happen in another child (assuming the same partner) is
1 in 4 (25%).
If the cause of your child's hearing loss is an
autosomal
dominant gene, then the likelihood that this will happen in another child (assuming one parent also has the gene for hearing loss), is
1 in 2 (50%).
If my child has an autosomal recessive condition causing hearing loss, what is the chance that they will have a child with hearing loss?
My child will pass a recessive gene. Their partner can be tested to see if they carry the altered recessive gene. If they are not a carrier, their children (my grandchildren) will be carriers but would not have hearing loss due to the recessive condition.
If we have an autosomal recessive hearing loss condition in our family, what is the chance my other children have the recessive gene?
- There is a 2 in 3 chance that hearing siblings (brothers and sisters) of a child with recessive hearing loss, carry the hearing loss gene (like you and your partner).
- If this is the case, then their partner could be tested to determine if they are also a carrier. If that partner is also a carrier of the same gene, then each of their children would have a 1 in 4 (25%) chance of having the same genetic hearing loss. If that partner does not carry the altered gene, then all their children would be unaffected, although each child would have a 50% chance of carrying the hearing loss gene.
- There is a 1 in 3 chance that hearing children of two carriers do not carry the recessive hearing loss gene. If this is the case, there is nearly a zero chance of having a child with hearing loss due to this gene.
Should I have my other children tested to see if they carry an autosomal recessive gene for deafness?
Whether your unaffected children should be tested to determine if they also carry the deafness gene is a matter of choice. Typically, siblings are encouraged to make this decision in adulthood. Your hearing children may want to know their own gene carrier status so they would know whether to have their partners tested to determine if their children (your grandchildren) have a chance of having hearing loss due to this gene.
Is this something that I need to be concerned about in my other relatives?
If you and your partner carry a recessive gene, then at least one of your parents and one of your partner's parents also carries the gene. This means that each of your brothers and sisters has a 50% chance of carrying the same altered gene.
Why is my child being referred for Genetic Testing?
Genetic testing may determine whether your child's hearing loss is due to changes in a gene resulting in hearing loss. Hearing loss has many causes. It is almost impossible to determine the cause of a person’s isolated hearing loss without genetic testing. With genetic test results, professionals can determine if there are other health conditions that should be addressed. Some diagnoses indicate whether progression is possible and if specific treatments have been successful in individuals with the same form of hearing loss. Genetic test results may allow clinicians to calculate the likelihood that additional children in your family may have hearing loss due to the same cause recurrence risk.
What is involved in genetic testing?
Tissue from blood, saliva, or a cheek swab is sent to a lab. A genetics laboratory identifies alterations in the genetic material called variants. We all have differences in our genetic material;
variants make us unique. The laboratory must determine whether a variant is not problematic (benign), or the cause of the condition (pathogenic). Sometimes the laboratory is unable to categorize the variant; this is termed a variant of uncertain significance (vus).
Do all gene variants affect health and development?:
MedlinePlus Genetics
How likely is genetic testing to identify a genetic form of hearing loss?
- One
study showed nearly 40% of all individuals had a genetic form of hearing loss identified through genetic testing.
- Three Characteristics most associated with a genetic form of hearing loss were:
- Hearing loss is present from birth (congenital).
- Degree and pattern of hearing loss is the same in both ears (symmetric).
- Hearing loss is present in at least one close family member (familial).
- Genetic testing may be worthwhile even when the child does not have these three characteristics.
- Approximately ten percent of tested individuals had a syndromic form of hearing loss when the hearing loss was thought to be isolated.
What do the results of genetic testing mean for my child?
Management of your child's hearing loss will be based upon the specific characteristics of your child and his or her communication needs. The findings from a genetic evaluation may be relevant for your child's medical care.
Genetic test results may suggest the hearing loss has balance (vestibular) problems and may be associated with progression.
Considerations for Genetic Testing
Is learning that I am a carrier of an autosomal recessive condition causing hearing loss bad for me?
Parents may feel bad that they carry an autosomal recessive gene, but it is important to note that we all have genes that are not working well. Recessive genes are no one’s fault. We do not control the genes we get from our parents, and we cannot choose which genes to give to our children.
Discovering that you have a gene should not affect whether you can get health insurance; however, laws that protect you today may not always exist. Life, disability, and long-term care insurance are not guaranteed. Some individuals investigate obtaining these insurances prior to having genetic testing.
How much does genetic testing cost?
Some laboratories will check with your insurance to determine coverage. Many laboratories offer genetic testing with sliding fee scales or self-pay options to make testing more affordable. Families should always check with their health insurance carrier to determine if genetic and medical tests are covered under their plan. A genetics professional can help navigate options.
