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Current time:0:00Total duration:9:57

Video transcript

so your next patient just walked in and his name is Joe and he's here because he hasn't been feeling so well he tells you that for the past few weeks he's been feeling really tired so just not like his normal self and he thinks that he's lost some weight so you check up on that and you find out that he's actually lost a significant amount of weight and he looks a lot thinner and weaker than he usually does so you talked to him you calm him down and then you start to examine him and right away you notice that his skin looks a lot paler than it usually does so this is what Joe normally looks like but today today he looks a little bit more like this and you noticed that he has bruises all throughout his body and when you ask him about the bruises he actually can't remember getting them he doesn't remember ever getting hurt and when you check his temperature you see that he has a fever so as you're finishing your exam he tells you well you know I've been feeling this pain throughout my body and it feels like the pain is inside my bones and inside my joints so he's also been having some bone pain so if you're worried about Joe then your instincts are on point because there's definitely something serious going on over here but at this point you probably don't know what that is is this infection is it cancer it's it's a rare crazy disease it's really hard to tell at this stage so you might start off by ordering some some basic studies some basic labs right and one of the labs that you might order would be a CBC and a CBC stands for a complete blood count and it's a really cheap and easy test to get but it tells you a lot of information so this is the typical information that you get from a CBC so it tells you the number of red blood cells that you have it gives you your hemoglobin and your hematocrit values which are indirect ways of measuring how many red blood cells you have it'll give you a platelet count and it'll give you a white blood cell count and these are the normal values just for reference so hint hint Joe has leukemia but we don't know that yet because we're still working him up so a CBC shows us that he has a decrease in his red blood cell count and that's called anemia and he also has a decrease in his hemoglobin and hematocrit and that's just from the decrease in the red blood cell numbers and he also has a decrease in his platelet count and that's called thrombo thrombocytopenia thrombocytopenia okay and finally he has a decrease in his white blood cell count and that's called leuco leukopenia but actually in leukemia you could also see an increase in the white blood cell count and that's because in leukemia eventually the leukemia cells run out of space to grow inside the bone marrow and when that happens they leak into the blood and you start to see them in the blood okay and these leukemia cells are usually usually immature white blood cells just because most leukemias are white blood cell leukemias so the person who's counting all of these cells who's giving us our CBC values sees these immature white blood cells sees these leukemia cells and he or she counts them as white blood cells and that's why you have an increase in the white blood cell count but if you looked more closely at the blood you'd see you would actually see that the number of healthy mature white blood cells is always decreased so this CBC is really concerning it tells us that our patient Joe has a shortage in the number of all of his blood cells and that actually accounts for most of the symptoms that he came in with so you should feel like you're heading in the right direction towards finding out what's wrong with him okay and you might wonder well what's causing the shortage in blood cells is the bone marrow not making enough blood cells or is the bone marrow making enough blood cells but then the cells are being destroyed after they're released into the blood and really the only way to answer that question is with a bone marrow Oh bone marrow aspiration no no so if this is a bone over here you could stick a needle inside the bone and inside this cavity in the center of the bone which is where the bone marrow is right and with this needle you could then draw out some fluid and then you could look at that underneath the microscope so in leukemia what would you expect this fluid the bone marrow aspirate to look like well I'm going to give you a couple of seconds to think about that while I draw the answer so I've drawn this diagram like a thousand times already but I just wanted to remind you that in leukemia your your immature blood cells you're crazy leukemia cells take over the entire bone marrow so much so that there's no space left inside the bone marrow so if you took a sample of this bone marrow it would show you two things so the first thing that I would show you is lots and lots of cells so an increase in the number of cells compared to what you normally expect to see and so we call that a hyper hyper cellular hypercellular bone marrow okay and hyper just means a lot and cellular means cells so hyper cellular bone marrow means a bone marrow with lots of cells in it and that's exactly what you get with leukemia and the second thing that you'd expect to see is lots of immature immature blood cells right which are called blast cells in a normal bone marrow do you see immature blood cells well sure because the mature blood cells have to come from somewhere right they come from the immature blood cells but in normal bone marrow only two to three percent of all of the cells are immature only two to three percent but in leukemia the number of immature cells is greater than two to three percent but it's not enough to say that it's just greater than two to three percent we need to quantify how much greater it is so in leukemia more than 20% of all of the cells in the bone marrow are immature or immature blood cells or or blast cells so if we do a bone marrow aspiration and we see that more than 20% of all of the cells that we're looking at are immature cells our blast cells then we know definitively that the patient has leukemia so you figured out what's wrong with your patient you diagnosed him with leukemia but it's not enough to stop there because you have to figure out what type of leukemia he has and that's important for being able to tell him what his prognosis is and for being able to determine what his treatment should be so the next step the next step would be to classify classify the leukemia and this can be done in one of two ways the first way seems the most intuitive to me and that is to look at the leukemia cell okay to characterize the leukemia cell so I want to take you back to this diagram which we use to talk about the development of the different types of blood cells and you can see the mature blood cells down here you could tell these cells apart in a snap they have such distinctive appearances but these blood cells up here the immature blood cells these cells pretty much look exactly the same so you can't tell them apart just by looking at them and remember that leukemia cells are immature blood cells okay so they look like these guys so going back to our leukemia cell that we're trying to characterize looking at the cell isn't going to be enough we're going to need to do more to try to figure out what type of cell it is so in order to find out what type of cell this is we look at what molecules the cell has on both on the outside and on the inside because different blood cells Express different molecules different unique molecules that allow us to identify them so I want to give you an example so for example lymphoblasts right which are immature lymphocytes or immature B and T cells have this protein inside their nuclei and a protein is called T DT the T DT and only the lymphoblasts have this protein so the mature lymphocytes don't have this protein and all the other types of blood cells don't have this protein so if Joe's leukemia cell comes back positive for T DT we know that his leukemia came from it originated from a lymphoblast another example another famous example is of a mile oblast remember that these are the immature blood cells that make the neutrophils eosinophils and basophils this is a myeloblast and a myeloblast has this protein this enzyme in its cytoplasm that's called my yellow myeloperoxidase myeloperoxidase you often see abbreviated as MPO and we can actually we have a paint we have a stain or a paint that bind to myeloperoxidase so we can take the leukemia cells from our bone marrow aspiration right and we can flood them in this stain in this paint and if the cells take up the stain if they become colored with the stain we know that the patient's leukemia originated from it developed from a mile oblast so that's the first way that you can classify your leukemia the second way is by is by looking for chromosome translocation remember chromosome translocation looks something something like this and we said that a lot of leukemias are associated with chromosomal translocations so you can look to see if your leukemia cell has a particular chromosome translocation that's associated with a particular type of leukemia and that will help and that can help you classify the type of leukemia and so this is how you diagnose leukemia