Genetic deafness is deafness caused by genetic mutations during fetal development. The genetic mutations responsible for hearing loss are either dominant or recessive. When a sperm and egg unite, the zygote receives 23 chromosomes from the mother and 23 from the father. These chromosomes contain the genes responsible for traits like eye color and hair color. If a gene mutation is dominant, a child only needs to receive one copy of the gene to inherit the disorder. If a mutation is recessive, the only way for a child to inherit a disorder is if he or she receives a defective copy of the gene from each parent. If a child is born with deafness, it is important to get involved in the deaf community as soon as possible. Joining a support group can help parents of deaf children learn about deaf culture and give deaf children the opportunity to meet other deaf people.
Causes of Genetic Deafness
Some deaf people are born with genetic disorders that cause other medical problems in addition to their deafness. Some of the most common dominant mutations are the ones for Branchio-oto-renal BOR syndrome, Waardenburg syndrome, Stickler syndrome, neurofibromatosis type II, and Treacher-Collins syndrome. Deaf people with BOR syndrome may develop cysts in the outer ear or on the neck. Some people with this disorder have malformed outer and inner ears. This disorder is associated with kidney problems, which puts people with BOR syndrome at risk for serious health problems.
Children with Waardenburg syndrome have very distinct features. These features may include premature graying of the hair, different-colored eyes, underdevelopment of the tip of the nose, and the presence of a white lock of hair. Some children with this genetic disorder also have partial albinism, which is a lack of skin pigment. Stickler syndrome occurs due to mutations of the gene responsible for the production of collagen and connective tissue. In addition to deafness, people with Stickler syndrome may have cleft palate, severe near-sightedness, retinal detachment, early-onset arthritis, joint disorders, and malformations of the middle ear bone.
Neurofibromatosis type II, also known as NFII, may cause progressive hearing loss. Children with this disorder may have cream-colored spots on their skin. In some cases, tumors grow on cranial nerve VII. This is what causes hearing loss. Some children develop cataracts due to the presence of NFII. Deaf people with Treacher-Collins syndrome may have malformed outer ears, narrow ear canals, problems with teeth alignment, underdeveloped cheek bones, and balance problems.
There are four common types of recessive hearing loss: Alport syndrome, Usher syndrome, Pendred syndrome, and Jervell and Lange-Nielson syndrome. Some children born with Alport syndrome have normal hearing at birth, but the disorder may cause progressive hearing loss. This condition is also related to cataracts, kidney problems, palate abnormalities, and near-sightedness. All three types of Usher syndrome cause hearing loss. Type I causes profound deafness in both ears. Type II causes moderate hearing loss from birth. Children with type III have normal hearing at birth, but become deaf during childhood or in their teens.
Pendred syndrome is a genetic disorder that causes deafness, inner ear malformations, and goiter. Goiter refers to enlargement of the thyroid gland, the gland responsible for producing certain hormones. Children with Jervell and Lange-Nielson syndrome experience sensorineural hearing loss, which is hearing loss related to problems with the vestibulocochlear nerve. This nerve is also known as cranial nerve VIII.
The deaf community is filled with talented, intelligent people. Many of them are willing to help new parents cope with the demands of caring for a deaf child. Members of the deaf community can also help parents and children learn about deaf culture and topics important to people who have hearing loss. One of the most important parts of deaf culture is educating people about the causes and effects of deafness. Deaf education programs are often given at hospitals, schools, churches, and community events, which makes it possible to share accurate information about deafness. Since deaf people are sometimes stigmatized by others, it is important for people to attend these deaf education programs. Lectures, workshops, seminars, and other deaf education events can help people understand that deaf people are just regular people who happen to have hearing loss.
The following resources contain more information about the causes of genetic deafness.
- Understanding the Genetics of Deafness PDF
- Genetic Deafness PDF
- Nonsyndromic Deafness
- Fast Facts on BOR
- Waardenburg Syndrome Overview
- Stickler Syndrome
- Neurofibromatosis Type 2
- A Guide to Understanding Treacher-Collins Syndrome PDF
- Usher Syndrome Information
- What is Alport Syndrome?
- Genetics of Pendred Syndrome