Learning About Your Child's Hearing Loss

What is hearing loss?

Hearing loss is when you lose some or all of your hearing in one or both ears.

What causes hearing loss?

There are many causes of hearing loss, including:

• Genetic causes (when a change in DNA is present and it is possible that one parent has hearing loss or carries a gene for hearing loss).
• Infections
• Drug interactions (when drugs don’t work well together and cause side effects)
• Structural problems with the ears, or problems with the way the ears form or develop during pregnancy
• Physical trauma to the ear (when the ear is damaged from an injury)
• Certain antibiotics, like gentamicin
• Having a virus during pregnancy, like toxoplasmosis, rubella, cytomegalovirus (CMV) and herpes

What are the different types of hearing loss?

There are 2 types of hearing loss that can have a genetic cause. These are syndromic and nonsyndromic hearing loss.

Syndromic hearing loss

In about 3 out every 10 children with a genetic cause of hearing loss, the hearing loss is not the only medical problem. This is called syndromic hearing loss.

Syndromic hearing loss happens in every 3 out of every 10 people with genetic hearing loss. In about 7 out of every 10 children with a genetic cause of hearing loss, the hearing loss is the only issue. This is called nonsyndromic hearing loss. The most common genetic changes causing nonsyndromic hearing loss are found in 2 genes called the Connexin genes (Connexin 26 and Connexin 30).

Syndromic hearing loss happens in every 3 out of every 10 people with genetic hearing loss.

Passing on genetic hearing loss

The pictures below show different ways genetic hearing loss can be passed from a parent to a child. Your doctor may be able to tell you which one applies to your family after genetic testing.

Autosomal recessive hearing loss

Autosomal recessive hearing loss is when both copies of the hearing loss gene do not work correctly. An affected child gets 1 copy of the non-working gene from each parent. There is a 1 out of 4 chance another child will have hearing loss.

Autosomal dominant hearing loss

Autosomal dominant hearing loss is when 1 copy of the hearing loss gene works correctly and the other does not. One nonworking copy is enough to show hearing loss features. There is a 1 out of 2 chance the child will have hearing loss.

X-linked or mitochondrial hearing loss

In X-linked or mitochondrial hearing loss, the gene for hearing loss is found on the X chromosome, one of the chromosomes that determines your child’s sex/gender. A mother can have the gene for hearing loss, but not the features. She would be called a carrier. A son has a 1 out of 2 chance of having hearing loss. A daughter has a 1 out of 2 chance of also having the gene for hearing loss and being a carrier. If a father has the gene for hearing loss on the X chromosome, a son will have NOT hearing loss since he gets the Y from his father to make him male. A daughter will have the gene for hearing loss, making her a carrier.

De novo hearing loss

De novo hearing loss is when 1 copy of the hearing loss gene works correctly and the other does not. One nonworking copy is enough to show hearing loss features. There is a 1 out of 2 chance the child will have hearing loss.

Autosomal dominant hearing loss

Autosomal dominant hearing loss is when 1 copy of the hearing loss gene works correctly and the other does not. One nonworking copy is enough to show hearing loss features. There is a 1 out of 2 chance the child will have hearing loss.

How do genetics work?

Everyone has 2 copies of every gene in their body. Our genes are the instructions that tell our body how to build and develop. A person’s genes determine his/her eye color, hair color, different disorders, height, weight and much more. Our genes are packaged into chromosomes. Everyone gets 1 copy of each chromosome from each parent. When you combine both sets of chromosomes from the parents, the child has a total of 46 chromosomes (23 from the mother and 23 from the father).

Chromosomes live in every cell in the body. When the body makes new cells, the DNA must copy itself over and over again. Sometimes, pieces of the DNA are left out or extra pieces are added in. These mistakes can cause different disorders, including hearing loss. These mistakes are random. They are anyone’s fault and are not caused by something a parent did or didn’t do.

Rev. 7/2017