Genetic Causes of Congenital Deaf-Muteness in Families

Q: Genetic Causes of Congenital Deaf-Muteness in Families

Hello： Whether a child is born deaf-mute cannot be immediately determined, and aside from hereditary diseases, it may also be due to genetic mutations (which are more common in advanced maternal age). <br>However, the probability of being born deaf-mute is generally low. <br>It i

Congenital deaf-muteness?

Hello, I would like to inquire about the genetics of deafness.
My brother has several girlfriends, and his mother is deaf.
She has a total of four siblings, all of whom are also deaf.
However, as far as we know, his grandmother was not deaf.
His uncle has also married and has children and grandchildren, none of whom are deaf.
Only the four children born to his grandmother are deaf.
I would like to ask what might be the cause of this.
Will my brother's future children be deaf? This issue is currently causing concern in our family.

Xiao Zhen, 20~29 year old female. Ask Date: 2007/04/05

Dr. Cai Jueren reply Family Medicine

Hello: Whether a child is born deaf-mute cannot be immediately determined, and aside from hereditary diseases, it may also be due to genetic mutations (which are more common in advanced maternal age).
However, the probability of being born deaf-mute is generally low.
It is recommended that your female friend and her fiancé undergo premarital health screenings at a hospital to ensure better health for their future offspring.
Thank you for your letter, and I hope the above information addresses your concerns.
Dr.
Tsai Jue-Ren, Hualien Hospital.

Reply Date: 2007/04/05

More Info

Understanding the genetic causes of congenital deaf-muteness can be complex, especially when considering family history and the potential for hereditary transmission. In your case, it appears that your brother's mother, along with her siblings, are affected by deafness, while their mother (your brother's grandmother) is not. This suggests a possible autosomal recessive inheritance pattern, which is common in conditions like congenital deafness.

Autosomal recessive conditions require two copies of the mutated gene (one from each parent) for the trait to manifest. If your brother's mother and her siblings are deaf, it is likely that both of their parents (your brother's grandparents) were carriers of the gene mutation responsible for deafness. Since your brother's grandmother is not deaf, she may have been a carrier without expressing the condition herself. This means that she could have passed on the mutated gene to her children, leading to the deafness observed in your brother's mother and her siblings.

In terms of your brother's future children, the risk of them being deaf depends on several factors, including whether he is a carrier of the same gene mutation. If your brother is not a carrier, then the likelihood of him having a deaf child is significantly reduced. However, if he is a carrier, and if his partner is also a carrier of the same gene mutation, there would be a 25% chance with each pregnancy for their child to be affected by deafness.

To better understand the genetic risks involved, genetic counseling is highly recommended. A genetic counselor can provide insights into the specific genes involved, the inheritance patterns, and the likelihood of passing on the condition to future generations. They can also help assess whether your brother should undergo genetic testing to determine if he carries the gene mutation associated with deafness.

It's also important to note that not all cases of congenital deafness are hereditary. Environmental factors, prenatal exposure to certain medications, infections during pregnancy, or complications at birth can also contribute to hearing loss. Therefore, a comprehensive evaluation of both genetic and environmental factors is essential in understanding the risks.

In summary, the situation you described suggests a hereditary pattern of deafness that may be autosomal recessive. Your brother's risk of having a deaf child depends on whether he is a carrier of the gene mutation. Consulting with a genetic counselor can provide clarity and guidance on the next steps to take, ensuring that your family can make informed decisions regarding future pregnancies.

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