Tuesday, February 3, 2009

Emma's Chromosomes

I plan on finishing the rest of the labor and delivery story later. I doubt anyone's at the edge of their seats to hear what happened next, because most of you already know the general story. However, I want to have it recorded before too much time passes and I also found it a little therapeutic to take the time to think about it and start to write it out. So it will be coming.

In the meantime, we got the results back from Duke University. As many of you know, we found a study that they were doing on anencephaly and decided that we wanted to participate. It required Tim and I to give them samples of our blood, answer lots and lots of questions in a telephone interview, and then donate Emma's cord blood for them to test after she was born.

As we suspected, Emma did have a chromosomal abnormality. Our perinatologist was the one who said she thought Emma might have one because in addition to the anencephaly, she had several other things that were wrong. The perinatologist suggested that Emma might have one of the trisomies (most likely 13 or 18). We opted out of the genetic testing anyways because only 5% of babies with anencephaly end up having something abnormal in their genetics. But when we decided to participate in the Duke Study, we learned that they would do it for us.

So the results. Emma did not have a trisomy. Emma was missing part of her Chromosome 1. The exact result was: 46,xx,del1p36. That means that she had 46 chromosomes, she's a girl (xx), and that there was a deletion on chromosome 1 on the short (or p for petite) arm. The 36 further specifies the spot, but obviously it was the end.

We found this out last Friday, but I was just able to speak with the geneticist again today to ask her more questions and to clarify some more things.

Here's what I learned:

In the 5% of babies with anencephaly that they find a chromosomal abnormality, the majority of them have Trisomy 18. That would mean that their test results would read 47, xx (or xy in the case of a boy). The other babies that fall in that 5% but do not have Trisomy 18, usually have random findings. Emma is the first baby in Duke's study (they've been at this since '93 or '94 I think) that has had a deletion on chromosome 1. However, the geneticist did some research and there was (or is, I don't know) a study in California and they too had one anencephalic baby that had a deletion on Chromosome 1. I guess just two babies is enough for the geneticist to think that there might be something significant there. But my guess is that will take a long time to figure out.

Now to enlighten you about Chromosome 1 and the actual deletion. Chromosome 1 is the largest human chromosome and represents about 8 percent of the total DNA in human cells. There is a specific syndrome for this deletion. It is called 1p36 deletion syndrome. However, neural tube defects are not associated with this syndrome. It is one of the most common deletion syndromes and occurs in one every 5,000 to 10,000 births.

What does it mean for us? Duke University is sending us another kit for some blood work to be done. They want to do some more testing on my blood. Because of their lack of funds right now, they are not going to test Tim's blood initially. If my results come back normal, they still might not test Tim's blood, but they'll decide when we get to that point.

Here's what wikipedia had to say on the matter:

Most deletions in chromosome 1p36 are new mutations, that occur before fertilization, during the formation of gametes (eggs or sperm). There have also been reports of patients with 1p36 deletion syndrome whose parents have a balanced or symmetrical translocation. This means a portion of one chromosome is transferred to another chromosome, so the parent has the "36" portion of chromosome 1 attached in an alternate location. When this occurs, cell division creates gametes that are missing a piece of 36.

In new mutations, the mechanism causing chromosome breakage is unknown. Deletions of paternal origin (father) are larger than the deletions deriving from the maternal (mother) chromosome. The majority of deletions are maternally derived. There do not seem to be differences in the clinical manifestations (the symptoms or observable conditions which are seen as a result of 1p36) based on whether the deletion is on the paternal or maternal chromosome.

I should also mention that the majority of facts from this post were either given to me verbally by the geneticist at Duke University that we are working with or taken from the wikipedia page on 1p36 deletion syndrome.

I'm not too worried about it at this point. Mostly because I don't think they'll find anything wrong with my chromosomes. Both the geneticist and the information from wikipedia lead me to believe that it happened on its own. But secondly, even if they do, I know that Heavenly Father is watching out for me and my family.



You did a great job at explaining this. I feel I understood it. I am glad y'all were able to participate in the study.

Kristen said...

I really wish you'd been my College Biology teacher - maybe I would have done better!

Bess Family said...

From a parent with a child with 1p36, thank you for posting Emma's story.