Okay, so the title of this post probably makes it sound WAY cooler than it actually is.....but I was kind of going for eye-catching. And it's technically true, even if the phrase is beefed up.
As you may have guessed, last week we got the results for the CSID genetic blood test that Max had done, back when they took tissue samples during the endoscopy. I was kind of on the fence about getting the genetic blood test done--after all, the enzyme level test would tell us whether he had CSID or not--but my nerdy genetic side won out. I just really wanted to know exactly what mutations he was walking around with(and subsequently what Sam and I at least carry). Plus, it was going to be a great time, when he was already asleep and it wouldn't hurt him at all. To put icing on the cake, the insurance agreed to cover its usual 80/20, even though there is only one lab in the US (Washington University Labs) that does the test.
Sold. And totally glad that we did. I must have done research on the results for a good hour after I read the report, trying to put some puzzle pieces together. It tickled me pink that I could put five years of a science degree and my boring molecular biology class to good use. Here's what I found out (hopefully in non-scary, easy to understand language):
The mutation for CSID lies on chromosome three, in the SI (Sucrase-Isomaltase) domain (area). It is approximately 1800 proteins long, which really isn't super big in the scheme of our whole genetic makeup. The first 1000 or so proteins are the isomaltase domain, and the last 800 belong to the sucrase domain. While the isomaltase domain is larger, there tend to be more mutations on the sucrase domain. As of 2011, I believe there were some 25 different mutations discovered in CSID--I'm guessing the number is a bit bigger now. The majority of these are missense issues with the protein.
That last sentence probably doesn't sound like English if you've never taken molecular biology, I know.....so time for a simplified biology lesson! Basically, every protein is composed of three different amino acids (which is why you will often hear amino acids referred to as the building blocks of proteins). There are four different amino acids, which each have their own "letter" (think of it as a nickname): adenine (A), tyrosine (T), cytosine (C), and guanine (G). If you do the math/chemistry--and thankfully somebody else already did it for me a long time ago--you can pair that "four amino acids in a set of three" combination 21 different ways. If you are doubting my math skills because you were crazy enough to do that algorithm, I will tell you that each protein has at least three different amino acid combinations that it can be coded for. So, you should just take my word for it.
Anyway, 21 different proteins can assort themselves in any order that they choose to make a domain (area) of genetic code, like the SI region I was mentioning earlier. As you can imagine, every once in a while the human body makes a mistake and sticks an incorrect amino acid "letter" into a protein. I won't even go into how our bodies assemble them and how the mistakes can happen, cause it's ridiculously complicated, but just know that mistakes happen. When one letter is mistakenly exchanged for another it is called a missense mutation in the biology world, like I was mentioning earlier. Some mistakes don't change the protein at all (because as I mentioned earlier there is more than one way to combine amino acids to code for the same protein), some change the protein but not the overall functioning of the domain (lucky pass!), and some mistakes change the function of the domain altogether (like in my boys with their sucrase and isomaltase enzyme activity level).
Okay, enough of the complicated stuff, sorry to put you all through that. As I mentioned earlier, there are 20-some known mutations that cause CSID. As the good laboratorians at Washington University tested more and more people, they realized there were 4 mutations that kept commonly popping up in people diagnosed with CSID. Of these, Max carries one gene for the third most common mutation, which shows up in approximately 7% of CSID patients. It is on the sucrase domain, in position 1745, and the letter G is replaced with T, which changes that particular protein from Cysteine to Phenylalanie. Not a good change as my boys can tell you! Okay, Max can't exactly talk yet, but that's beside the point. I think this is the mutation that Sam carries. Sam has always had more issues with sugar than I have, and seeing as this particular mutation is on the sucrase domain, it would make sense.
The other mutation Max has is on the isomaltase domain in position 975, and the letter C is replaced with T, which changes that particular protein from Histidine to Tyrosine. And here's where the title of my blog post comes into play.......it is a mutation which hasn't been discovered before. Ever. Kudos to us for being weird enough to breed that lol. Actually, I guess the real kudos go to whoever originated the mutation. I suspect Max inherited this mutation from yours truly--I don't tolerate starch all that fabulously the more I think about it--, and if that's true, I'd bet this one came from my daddy (if I actually have CSID anyways....if I only carry it I change my vote to my mom). Beyond there it beats me. But thanks long gone ancestors for throwing this one out there.
Obviously to prove any of my theories about who carries what, Sam and I will both have to have the genetic testing done as well. Once again, the nerdy side of me is kind of stoked. However, the practical side of me (and probably Sam) is a bit leary. What if one of us actually has CSID? Or worse, what if we both do? We have two children with CSID, and we love them to tears, but it's not exactly something you want to just keep passing on. It's expensive to keep up with, and a real social misery. If we are both carriers, there's just a 25% chance of passing it to each child. If one of us has it and the other carries, that goes up to 50%. And obviously if we both have it, all of our kids will have it. And before you say "Well wouldn't you know if you had CSID since it was so obvious with your kids?" let me just say no. If you've lived your whole life with things a certain way, it doesn't seem so odd after a while. And every person is symptomatically different, I believe due to the combination of mutation(s) you carry.
If we do have CSID after all, do we change the way we eat and ultimately feel better, or continue to enjoy the foods we've been eating for years and just suffer on? Because I've got news for you--my toddler might not know that coconut flour bread makes kinda gross sandwich bread in comparison to regular flour, but I sure do. And honestly I really love a good piece of fruit when the urge strikes (although I guess Sucraid could assist with that). So many things to weigh out.
Last interesting thought. I've often wondered why a lot of other people's kids have more tolerance to starches in CSID than Jayson has ever seemed to. I'm starting to think a lot of people who have CSID just possess mutations on the sucrase domain. While it obviously doesn't protect you entirely from starch intolerance, I think having a mutation on the isomaltase domain gives you much less starch tolerance, and much less chance to ever build more tolerance. All my theoies people, but they do make logical sense.
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