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Cystic Fibrosis: Part 1


Let’s talk about some specific, genetic abnormalities and we’ll talk for a minute about cystic fibrosis and sickle cell anemia. So, more choices. Okay. So we’ll talk for a minute about cystic fibrosis. What is it? It’s an inherited disease. It’s a situation where essentially we get mucous which is supposed to be slimy and slick, right? Terrible thing to talk about, but when it gets all dried out and yucky like old dried out hair gel, it doesn’t do its job very well. And it’s supposed to get things moving through the body so, for example, getting junk out of the lungs and helping things flow through the intestines. So when the mucous gets all clogged up like that, old dried up hair gel, then it causes problems in those systems. So, for example, it can cause mild or severe disease in many situations. Some times people have very few troubles, and sometimes people have lifelong troubles that are very bad. But the bottom line is we don’t know how to fix it. So it’s a lifelong situation that we have to deal with if people have cystic fibrosis.

So first of all, we should talk about what happens in the lungs in people with cystic fibrosis. They get clogged up. So you can imagine, if you breathe in normally like we all have to breathe normally, we take in bacteria sometimes as we take breaths. And the bacteria go down into the distal airways, but the mucous helps get the bacteria out of there. So if you’ve got thick clogging mucous and the bacteria can’t get out of there, then you get bacteria stuck down in the lungs and you can end up having recurrent infections. So people end up coughing and wheezing a lot, and if they get these kinds of infections, then they get treated with antibiotics. The problem there is that eventually these bacteria get resistant to the antibiotics, so that sometimes we get to the point where we don’t have antibiotics that work anymore on people who have recurrent pneumonias.

So we have to figure out how to deal with that. That’s one of the biggest issues. Beyond lungs, we’ve got sinuses and the sinuses also need drainage and to keep things moving through there, to work normally. So if you get thick mucous in there, then people get recurrent sinus infections and that can cause troubles.

What about the intestines? Well, stuff’s got to move through there, right? And people with cystic fibrosis, they sometimes get digestive problems. They sometimes have to take extra enzymes to help with digestion, to help keep things moving through like they’re supposed to. Men who have cystic fibrosis can be infertile because their tubes get clogged up so you can’t get the sperm from the inside to where they need to get, and so that can cause fertility problems. And women who have pregnancies while they have cystic fibrosis with the lung issues and things that can cause them some challenging pregnancies.

And actually one of the other issues is that people with cystic fibrosis, in addition to their recurrent infections, sometimes they develop and have troubles dealing with diabetes. You had mentioned diabetes earlier and it can be caused by cystic fibrosis. So, in a woman who had cystic fibrosis, that could further complicate her pregnancy if she had diabetes. The good news is that, in some sense, people who have cystic fibrosis can grow normally. They have normal intelligence. So, it can be a challenge but people are doing well and people are living longer now. Now that we have better and better antibiotics, people are living longer and longer. So kids that are born nowadays, who have cystic fibrosis, on average they’re going to live into their fifties or beyond. And hopefully by the time they get a little older, we will have sorted this out and know how to fix it. So we’re hopeful that we’re going to make some changes with cystic fibrosis for the good.

Now talking about all of this may sound like everybody’s got it. Right? Hopefully not. It’s not that common but it is most common. It happens in about one in three thousand pregnancies in women, in families … Caucasian families, or families of Ashkenazi Jewish descent. That’s Eastern European. So how do you diagnose it? Well, you diagnose it by how much salt is in the sweat. People who have cystic fibrosis have salty sweat, but we can actually diagnose it by the clinical findings because of the recurrent pneumonias and things like that. So if children keep coming in and they keep having pneumonias, then they’ll test them and see if they have cystic fibrosis.

We can also test the DNA. We now actually know what abnormalities in the DNA … we know the gene that’s associated with cystic fibrosis. So that when there are mutations or abnormalities in the cystic fibrosis gene, we can detect those and tell if people are going to get it. So what that means is that you could test somebody before they became symptomatic. Now let’s remember genetics. At the beginning, we spent some time talking about how we get a chromosome from mom and a chromosome from dad. So all genes come in pairs essentially. And to have cystic fibrosis, you actually have to have one abnormal gene from mom and one abnormal gene from dad. So what that means also is that people who have one abnormal gene can be normal. They act normal. They don’t seem to have any medical conditions so they’re basically what we call carriers. You can carry a disease and not know that you’re carrying it unless you had two copies of the diseased gene. Okay, does that make sense? All right. So remember carriers are totally normal and it takes mutations in both genes. The one from mom, and the one from dad, for a baby to end up having cystic fibrosis. All right.

So, if we had a couple and let’s say mom was a carrier and she might not know it, right? And dad’s a carrier and he doesn’t know it, presumably. So half of mom’s eggs and half of dad’s sperm would have the cystic fibrosis mutation, and half would be normal and so forth. So if they had a baby, there’s really four different possibilities. You could have the situation where the normal egg matches up with the normal sperm, right? If you had a normal egg and a normal sperm, what do you get? A normal baby. A normal baby, yeah. So you could also have the situation where the abnormal egg came together with the normal sperm or the abnormal sperm came together with the normal egg and then those babies would be what? Carriers. Yeah, they would be carriers just like their parents. So they’re kind of showing they’re halfway between normal and not normal, but they would clinically be normal. Right? Cause they would seem normal. All right, and so obviously then you could have that fourth possibility where the baby got the mutated gene from mom and the mutated gene from dad and then that baby would have? Cystic fibrosis. Cystic fibrosis. Right.