Acute leukemia | Hematologic System Diseases | NCLEX-RN | Khan Academy


Voiceover: So, now we can talk about the different types of acute leukemias. And remember that acute
leukemias come from these cells. So, the most immature types of blood cells that you can possibly
have, and we can split up the acute leukemias
into ones that come from myeloid cells, so these cells, so the acute myeloid leukemias, or the leukemias that
come from lymphoid cells, so the acute lymphoid
leukemias, and we’re going to start off by talking about
the acute lymphoid leukemias. So, I took that big diagram,
and I shrunk it down, and I stuck it into the corner because, to be completely honest,
nobody memorizes this diagram by just looking at it one or two times. You have to keep looking
at it over and over again, in order for it to stick inside your mind. So, if at any point you’re like, what cell is she talking about, just look up at this diagram
to help you reorient yourself. So, I said that we were going
to start off talking about these guys, so the acute
lymphoblastic leukemias. That’s often abbreviated ALL, so we don’t have to write it all out again. So, one of the things that I really loved about learning the
different leukemias was that the name of the leukemia told
you a lot of the information that you needed to know about it. So, the word leukemia tells
you that you’re dealing with a cancer of the blood cells. Well, what type of blood cells? So, this is a lymphoblastic
leukemia, so we’re dealing with lymphoblasts or immature
lymphocytes, immature B and T cells, and just how
immature are those cells? So, if this is an acute
leukemia, we’re dealing with the most immature cells that
you could possibly have, and really, that’s the
majority of the information that you need to know about this disease. A couple of other important
things is, number one, ALL is the most common cancer in kids. So, unfortunately, it affects
the little ones the most, and it’s also associated
with Down syndrome, with Down syndrome, and you
may know that Down syndrome is a genetic syndrome, where you end up with three copies of chromosome
21, and in a normal cell, you only have two copies of chromosome 21, but in Down syndrome, you
end up with an extra copy, so, you end up with three in total, and that’s called Trisomy 21. Well, it turns out that
chromosome 21 has this gene on it, and that gene makes a
protein that can damage DNA. So, the idea is, among other
ideas, that because you have an extra gene, you end up
with more damage to your DNA, and that increases your
risk of getting ALL. So, let’s say that you have a patient, a really young patient who’s
showing signs and symptoms of leukemia, so you go ahead and you get a bone marrow aspiration from
him, and if the patient has ALL, you’d expect that
when you looked at the aspirate underneath the microscope,
you’d see lots of lymphoblasts, because ALL, after all, is just a cancer of lymphoblasts, right? But what do I mean by you’d
see a lot of lymphoblasts? Because lymphoblasts look like all of the other immature blood cells. They look exactly the same,
and it’s not like they’re carrying around a sign saying, hey, I’m a lymphoblast, right? Or are they? Well, they kind of are,
because remember we said that all lymphoblasts have this protein inside their nucleus called TdT, TdT, and only the lymphoblasts have this, so none of the other blood cells have it, and not even the immature
lymphocytes have it. So, it kind of is like a sign
that they’re carrying around, saying, hey, I’m a lymphoblast. So, if the cells in the aspirate have TdT inside the nucleus, then you can go ahead and diagnose the patient with ALL. So, moving on, since there
are two different types of lymphoblasts, you’d
think that there would be two different types of ALL, and there are. There are two different types of ALL. The first one is called
the B cell, B cell ALL, and the second type is
called a T cell ALL. And we’re first going to
talk about the B cell ALL, so that’s this guy over
here, and going back to our patient that we did the
bone marrow aspiration on, we said that in his aspirate there were lots of lymphoblasts, but
how do we tell if that’s a T lymphoblast or a B lymphoblast? So, there are lots of markers
that only B lymphoblasts will have, and there are other markers that only T lymphoblasts will have. So certainly you could use those
markers to tell them apart, but there’s another really
nifty feature of B cell ALL’s that you could use to tell them apart, and that is that B cell ALL’s are associated with translocations, so chromosome translocations. So, we know that there are
lots of different leukemias that have translocations
associated with them, right? But a B cell ALL has two very specific translocations associated with it. The first is a t, t for translocation, t (12;21) translocation,
and all that means is that chromosome 12 and chromosome 21 each have a segment that’s shifted
onto the other chromosome. And the second type is
a t(9;22) translocation, and the first, and the
t(12;21) is usually found in kids who have B cell
ALL, and the t(9;22) is usually found in adults
who have B cell ALL. So these translocations are
really helpful or super helpful. First, they help us diagnose the disease, and, secondly, they help us determine the prognosis of the disease,
and I say that because it turns out that the
t(12;21) translocation is associated with a better prognosis, and that’s because the
leukemia cells that have this translocation inside
them, the cells themselves are more responsive to
treatment, to chemotherapy, and that’s for a whole
bunch of scientific reasons, but the way I like to think
of it, is that 12 and 21 are mirror images of each other. So, I like to think,
I like to imagine that there’s a mirror in
between them, and this is my really poor attempt at
drawing a pistol, a gun, and the gun is shooting
therapy, chemotherapy at the mirror, so that
leads to this explosion that kills lots of cells
around it, and I know it’s a really silly way of thinking of it, but for some reason, I haven’t
been able to forget that 12;21 means better response to therapy, and sometimes a bad analogy is more memorable than
a good analogy, okay? So, that’s B cell ALL. Now, the other type of
acute lymphoblastic leukemia is a T cell ALL. So, now we’re talking
about this guy over here, and I want to start by asking
you, when the bone marrow releases T cells into the
circulation, into the blood, where do the T cells go? Well, usually, they go
right into the thymus, and they go there so that they can develop a little bit more. So, in T cell ALL, you have lots of T lymphoblasts in the
blood, and they can also go to the thymus, and if
they do, your thymus will get bigger, and it’ll
feel like there’s a mass, a mass inside your thymus,
and that’s a problem because if your thymus is growing larger, it can compress the structures around it. So, it can compress the airway, and it can compress the esophagus, and that’ll lead to a whole
slew of symptoms on its own. So, you can get a thymic
mass, and the other thing that’s important is that T cell ALL’s are most often seen in teenagers, and something that might help you remember these three things is
remembering the letter T. So, T cell ALL is
associated with thymic mass and found in teenagers, okay? So, those are acute
lymphoblastic leukemias. Now, let’s move on to our
acute myeloid leukemias. So, that means in this diagram we’re looking at these guys over here. We’re looking at the
acute myeloid leukemias, myeloid leukemias. And because there are many
types of myeloid cells, you can have several different types of acute myeloid leukemias, and then, acute myeloid leukemia is abbreviated AML. So, for example, you could
have an acute myeloid leukemia developing from a myeloblast,
so this cell over here, and that would give you,
and that would be called, an acute myelo- myeloblastic leukemia. You could also have an AML that develops from a monoblast, and that would give you an acute monoblastic
leukemia, and in the same way, you could have an AML developing from a megakaryoblast, and that would give you an acute megakaryo-
megakaryoblastic leukemia. And you could actually get a leukemia, an acute myeloid leukemia developing from an erythroblast, but
that’s so extremely rare that you won’t really
hear people talk about it. It doesn’t really happen
in the real world, but it’s good to know that it’s
possible, theoretically, right? So, those are all of the different types of acute leukemias. Now, we’re ready to talk
about the chronic leukemias.

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