Biology 101

I wish I would have paid more attention in my 10th grade biology class, or that I would not have avoided taking biology in college like I did. The genetic studies would really come in handy now, as I struggle to understand Drew's genetic results for his hearing loss.

I understand the connexin abnormality. I carry one abnormal copy of connexin 26, passed to me from one of my parents. My husband carries one abnormal copy of his connexin 26 gene, passed to him from one of his parents. In Drew these two abnormal copies met up, causing his hearing loss.

What I can not understand - and what I am most worried about - is the mitochondrial abnormality that I passed to Drew. This is a very rare genetic disorder, so I contacted Dr. Choo with several questions regarding this abnormality, primarily because of the conflicting information I am finding in my Internet research.

I had thought after reading one site that the mitochondrial abnormality is X-Linked. I now know that is not the case. The mitochondrial abnormality is different, and generally is passed to each offspring of an affected mother. The concern I have is that if this mitochondrial abnormality did play a role in Drew's hearing loss, what concern should I have that my daughter will progressively lose her hearing?

From talking with Dr. Choo, he can not tell if the mitochondrial abnormality had any part in causing Drew's hearing loss. We know the connexin 26 abnormality certainly can cause profound hearing loss. In order to determine if the mitochondrial abnormality played a part in the hearing loss, Dr. Choo recommended that I have my DNA tested to see if I carry this abnormality. If I do, Dr. Choo believes that this abnormality in my families genetic make up does not cause hearing loss because I do not have hearing loss. If I do not carry it, it is possible, although very rare, that this mutation popped up "de novo," as a brand new genetic mutation in Drew. (The good news is that because the mitochondrial is only passed from mothers to their children, Drew will not be able to pass this on to his children.)

I am so thankful that I am working with Dr. Choo. Cincinnati Children's has a large research program on the genetics of hearing loss. I am confidant that with further testing, Dr. Choo will be able to locate the primary cause of Drew's hearing loss and will be able to tell me the risk factors for those in my immediate family.

With the genetic testing now complete, Dr. Choo has medical proof that the diagnostic hearing tests of Drew are accurate. He told me that this makes a Cochlear Implant medically necessary, and that it is very possible we will be able to have the surgery approved prior to him turning one year old. Finally, some wonderful news!