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More Genetic Testing

Posted Oct 17 2008 9:01pm

The past week has been a whirlwind, as I am trying to understand Drew's genetic test results, and determine where to go from here. I have learned a lot about both his connexin 26 and mitochondrial abnormalities. As I have discussed before, the mitochondrial abnormality is the most worrisome, as it can affect others in my family. Here are some of the steps we will be taking in the immediate future:

1. I will be having a DNA test run in the next week or so to see if I carry the same mitochondrial abnormality as Drew. If I do, I am at risk for hearing loss. In some, the hearing loss is apparent at birth (like Drew), and in others it is only induced by certain aminoglycoside antibiotics. I have read that I have a 100% chance of losing my hearing by the time I am 60 years old if I carry this mitochondrial abnormality and have ever had one of these antibiotics. There is a possibility, however, that this mitochondrial mutation popped up "de novo" in Drew and that I do not carry this mutation.

2. We will be having our daughter's hearing screened. As a result of the genetic testing, there is now hereditary hearing loss. It is recommended that all children in families with genetic hearing loss be evaluated yearly until they are six years old. Our audiologist will set a benchmark with our daughters' hearing, and then evaluate it each year to see if she has any loss. We will know more about any risk for her after my DNA test results. If I do in fact carry the mitochondrial mutation, it is very likely that she carries the mutation as well. Generally the mutation is passed to all children of an affected mother. That being said, she would be at risk for hearing loss from the aminoglycoside antibiotics. Knowing this information could prevent deafness in both of us.

3. Our daughter will also have a DNA test run to see if she carries the connexin 26 gene recessively and if she has the mitochondrial mutation. Even if I do not carry the mutation, I could have passed it on to her. Again, the more information we have, the better we will be at preventing hearing loss in her. Knowing if carries the connexin abnormality will help her in the future to know her possibility of having a child with hearing loss.

4. Pending the results of my DNA test for the mitochondrial abnormality, my sister will be tested for these abnormalities. If I carry the mutation, she most likely does as well, since it likely would have been passed to both of us from our mother. (This mutation would not affect my brother's children, since it is only passed from the mother. He would, however, be at risk for the amnioglycoside deafness. He may be tested for this at a later date). This will allow my sister to know if there is any possibility of passing this mitochondrial mutation to her children. She would only be at risk of having a connexin baby if her husband also carries the connexin 26 gene recessively. Since only three out of every 100 people carry this abnormality, it is highly unlikely.

Again, if you have any questions regarding testing for genetic hearing loss, please feel free to email me. Or, you can get information on testing for genetic hearing loss from Cincinnati Children's Hospital.

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