It is estimated that half of the children born with hearing loss have a genetic cause.1 Genes make up DNA -units of heredity that are passed from parents to children. If a gene does not form normally, it is called a mutation. Some of these mutations cause hearing loss.
Genetic hearing loss can be the result of non-syndromic or syndromic genetic mutations. Non-syndromic hearing loss is a hearing loss that occurs with no other symptoms. These mutations account for about 70% of cases of genetic hearing loss. Non-syndromic hearing loss can vary from person to person, even within the same family. Hearing loss can affect one (unilateral) or both (bilateral) ears and can range from mild to profound degrees of hearing loss. The hearing loss may also be stable or progressive, meaning that it can change over time.
Non-syndromic hearing loss is inherited in one of the following patterns:
- Autosomal recessive
- Autosomal dominant
- X-linked
- Mitochondrial
In an autosomal recessive inheritance pattern, the mutated gene is inherited from each parent. Most instances of non-syndromic hearing loss are inherited through an autosomal recessive pattern. There are currently more than 60 known genes that can cause autosomal recessive non-syndromic hearing loss. The most common cause of autosomal recessive non-syndromic hearing loss is because of a genetic mutation in the GJB2 gene which is a member of the Connexin protein family.2
An autosomal dominant inheritance pattern occurs when the mutated gene is inherited from only one parent. More than 30 genes have been associated with autosomal dominant non-syndromic hearing loss.2
In an X-linked inheritance pattern, the mutated gene on the X chromosome passes from the mother to the son and results in male children having a hearing loss. Approximately half of X-linked non-syndromic hearing losses are the result of a mutation in the POU3F4 gene.2 There have also been mutations identified in at least 3 others genes.
Mitochondrial genetic disorders are caused by mutations in DNA. Very few mutations have been identified in mitochondrial non-syndromic hearing loss and their role in hearing and hearing loss is still being studied.
Role of an Audiologist
Audiologists identify, diagnose, and provide treatment options for patients with hearing loss and dizziness. They work closely with physicians and speech-language pathologists and are an important part of the management team.
If you or someone in your family has been diagnosed with a hearing loss and you have concerns regarding a non-syndromic hearing loss talk to your doctor or Audiologist. Find an Audiologist near you to schedule an appointment.
References
1 “Hearing Loss in Children.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 18 Feb. 2015, www.cdc.gov/ncbddd/hearingloss/genetics/html.
2 “Nonsyndromic Hearing Loss – Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, 6 Feb. 2018, ghr.nlm.nih.gov/condition/nonsyndromic-hearing-loss#.
