- [Voiceover] Cystic fibrosis is one of
those names that doesn't
really describe what the disease is.
I mean, fibrosis, it's a lot of scarring and cysts,
we think of fluid-filled sacks
and this does come into play
in the pancreas as we'll see later.
But for now, just think of cystic fibrosis
or what we usually just say CF,
as just a name for this disease
and we'll find out step-by-step what it actually describes.
First, cystic fibrosis is a genetic thing,
so, it comes from our genes or is encoded
in our DNA.
I'm trying to draw the double helix
of the DNA right now...
like that, and we get this, of course,
from our parents.
Humans have 46 pairs of these.
You get one from mom, one from dad,
Cystic fibrosis is a recessive disease
as opposed to dominant.
In very simple terms, recessive
and dominant just refer to how many copies
of the defective genes you need to have the disease.
If we think of the CF gene as having
two different variations,
for most people, it's a normal gene.
Let's use big B, that's normal.
Then, for the gene with cystic fibrosis,
we have a little b.
Remember that the little b carries
the mutation for cystic fibrosis
You can get one from mom, one from dad.
Out of these two, there are
three possible combinations.
We have big B, small b, that's one.
We can have big B, big B or small and small.
For recessive diseases, you have to have two copies
of the defective gene so mom and dad
must give you the CF gene for the disease to happen.
This is different from dominant diseases where it only
takes one copy of the defective gene.
Let's do a quick genetic lesson here.
If we have two people having kids
and both of them carry the CF gene
but they don't have it,
remember, you need both copies of the little b to have it
so they both have the little b but neither of them
has the actual disease
and then get together and have kids.
There are four different combinations between
their two copies of genes.
For this square we get big B and big B.
Does this person have CF?
No, they don't have the CF gene at all.
For this person, they carry the copy
but just like their parents, because
they only have one copy,
they don't have the disease.
Same with trial number three,
but for this last one, you get small b and small b
and this child has CF.
For this particular combination,
it's one and four
so you can imagine the math gets a little more complicated,
depending on what the parents have.
All of this to say that cystic fibrosis
is something that's passed on genetically
and whether or not a person gets it depending
on what their parents have for the CF gene.
The studies and the numbers show us that this disease
is most common among the Caucasian population
just because of the frequency of the small b,
the CF gene in this population.
Since there's the highest frequency of CF genes
within the Caucasian population,
traditionally, they have been most affected by this disease.
Out of 3,000 people in the Caucasian population,
one person would have CF.
They would have this little b, little b combination.
For other races, traditionally there has been
less frequency of the disease
because the gene is not as frequent.
For example, in African people,
there's about 15,000 people who get
one person with CF
and in Asians, there's about one in 30,000.
Now, these numbers of course change all the time
but the point is, the more frequent a gene is
in a population, then there's more chances of you getting
little b, little b.
What is actually defective
about the CF gene is it's a gene that
controls the transport of two little ions.
One is chloride and the other one is sodium.
This is the chemical symbol for sodium.
Chemistry is really interesting because
sodium chloride together,
that's table salt.
That's what we eat,
but these molecules are in our bodies.
They do different things at different places.
The CF gene controls how they behave
and this is the thing that's defective.
As a result, we get all these problems.
It's like if you have a machine made
of tiny little cogs of all different shapes and sizes
and they're just held together and for the machine
to work, every piece should do their job.
There's one piece, let's say, this size
that just keeps having problems
so the same piece is in different parts of the machine
with different jobs
and when they're defective
because genetically, it's defective,
then every time you get to the CF gene
something is wrong
so the symptoms that we see are all over the body.
It's not concentrated in one organ.
One of most heavily effected organs
and also the place where most CF patients
have a lot of trouble Is the lungs.
You might think, "How does chloride
"have to do with the lungs?
"Why does it make such a big difference?"
The thing is, our lungs are lubricated by all of this mucus
and chloride and sodium play a big part in how much mucus,
what's the concentration of it,
so when they are malfunctioning,
then the nature of the secretions change
so it is a nice mucus that coats the lungs
and let it function normally, we get these thick secretions
that clog up the lungs.
With that, you get a lot of infections
because it's almost impossible for them to
clear all that thick mucus out of their lungs.
Infections.
To make matters worse,
that environment they have foster infections
that we wouldn't even commonly see.
For example, there's something called Pseudomonas.
A Pseudomonas infection is very rare in a person without,
in a healthy lung basically but in CF patients,
it's very prominent
and it's harder to treat.
Also, it's just hard to take a real good breath
with all that gunk in there
so the O2 concentration might be low.
Since it's hard to cough up all that mucus,
you'll see CF patients have to wear this vest
for maybe 30 minutes a day that's plugged to
a machine that just mechanically shakes
out the mucus in their lungs.
It's a standard therapy for people with cystic fibrosis.
Another big area that is a huge problem with
cystic fibrosis is the digestive tract
so we in particular have the pancreas and really,
just the GI system in general.
The pancreas is an organ that's tucked under
the diaphragm there and its main job is to secrete
all these things to help us digest our food.
Same thing with the secretions here
so when it's all clogged up,
the enzymes are supposed to come out,
can come out so especially when these patients are children,
it's hard for them to get the nutrients they need to grow
so even if they eat a good diet a lot of times
they're malnourished because the nutrients don't get
absorbed into their system...malnourished.
In a similar way, the liver is on the opposite side
of the stomach as the pancreas.
It secretes bile.
All this mucus again in the ducts
and the bile can't get out.
Bile helps us emulsify the fats that we eat and digest it.
The pancreas also gives us insulin.
Insulin is the chemical that
helps us regulate the blood sugar
so with the lack of insulin,
a lot of times, these patients have symptomatic diabetes.
Definition of diabetes is not being
able to control your blood sugar.
So, if you don't have insulin,
it's like they have type one diabetes.
With the malnourishment, the diabetes,
the lack of digestive enzymes,
kids with CF often have trouble
reaching their full stature
so their growth is usually restricted.
As you can see,
one little gene that controls
the transport of these two molecules.
I'm trying to show you
that it goes to the lung, the pancreas,
everywhere in the body really
and our treatments tend to revolve around
how to control the symptoms of these problems.
There are symptoms in CF
that's not really treated.
For example, since sodium and chloride makes salt,
oftentimes, their sweat in their skin
just tastes more salty,
but that's not something that affects
people's health so much so that's not treated as much.
The point is, cystic fibrosis shows up in so many ways
throughout the body and going back to the name,
why do we call it cystic fibrosis,
this is describing the scarring that occurs in the pancreas
as a result of the disease, you have these cysts
then you have scarring from all the blockage and the damage
to the tissue that leads to.
That's why I said cystic fibrosis is not that
descriptive of the disease
but just remember, it's really a group of symptoms
that all happen because of this recessive gene
controlling sodium and chloride.