Understanding the Genetics of Hearing Loss
Hearing loss affects countless people worldwide, and it also comes in a range of severity. The causes of hearing loss are equally numerous, ranging from aging, injury, excessive noise exposure, or diseases such as meningitis or Meniere's disease. However, the CDC estimates that 50 to 60% of children with hearing loss inherit their condition genetically. Here are the different ways an individual may genetically acquire hearing loss.
Autosomal Recessive Hearing Loss
Many genes associated with hearing loss are recessive, meaning that someone needs two copies of the gene, one from each parent, to have hearing loss. The National Institute of Health (NIH) estimates that 75 to 80% of inherited hearing loss comes from a recessive gene. With recessive genes, both parents may have perfectly fine hearing, which means they're "unaffected carriers," and the gene could have been passed along for generations without making itself known.
Autosomal Dominant Hearing Loss
Autosomal dominant hearing loss requires only one parent to pass along the gene. This often means that the parent also has some degree of hearing loss, and other family members may, as well. However, this type of genetic hearing loss may also appear for the first time as the result of a new genetic change. Dominant-gene hearing loss causes 20 to 25% of genetic hearing loss cases, according to the NIH.
X-Linked (or "Sex-Linked") Hearing Loss
When the hearing loss gene lies on the X chromosome, it is known as an X-linked or sex-linked gene. According to the NIH, between 1 to 2% of genetic hearing loss is X-linked. Because females carry two X chromosomes, they may not display the effects of the X-linked genes at all, or they are more likely to have a less severe degree of hearing loss compared to males. Males, however, have only one X chromosome, so any gene on their X chromosome will be expressed (this is the same reason why males are more likely to be colorblind than females). Fathers with X-linked hearing loss cannot pass the condition to their sons.
Mitochondrial Genetic Hearing Loss
Mitochondria are known as the powerhouses of the cell, and they produce energy that allows cells to function. Errors or alterations in mitochondrial DNA, therefore, may affect the functionality of any part of the body. When mitochondrial gene alterations affect the ears, it may reduce the ears' functionality. The NIH estimates that less than 1% of genetic hearing loss results from mitochondrial DNA.
When children display signs of hearing loss from birth or a very young age, it could very likely to be due to their genetics. Even if you don't have any hearing loss, if you believe your child may have reduced hearing, they should have a hearing assessment. High Level Speech & Hearing Center provides comprehensive hearing services to people of all ages in New Orleans, including hearing assessments and helping to find appropriate hearing aids. Schedule an appointment with us by calling 504-345-2984 today.