Transcription
Hey guys, let's talk about pure red cell aplasia. This is mythical; she's perfection, Alice. Another day, another video about a Nemean. It's a series in hematology. Go to my playlist named Hematology Oncology.
In a previous video, we have talked about aplastic anemia. This video is kind of related to aplastic anemia, with a huge difference. So please watch my previous video on aplastic anemia first. Anyways, pure red cell aplasia: pure means only red cell; it will not include the white blood cells; it will not include platelets; only the RBC's. That's why it's called pure. Aplasia means like growth, expansion, genesis; aplasia—no growth. There is no growth of that red cell line, and it's pure because the white blood cells and platelets are not involved. Big hero here is parvovirus B19. Symptoms of anemia are kind of the same here; the red blood cell kind of surprised because parvo is attacking her.
So the main difference between aplastic anemia and pure red cell aplasia is whether there is pancytopenia or not. In aplastic anemia, there was pancytopenia; all of the cell lines were involved. In pure red cell aplasia, only the RBC's are affected; white blood cells and platelets are completely normal. So there is no pancytopenia in pure red cell aplasia. I hope this is clear.
So again, hematopoiesis, stem cells, then we go down myeloid and lymphoid, and here is the red blood cell line. Only the RBC line is affected; all of these are completely normal. The story of MCV again: microcytic, normocytic, or macrocytic. In aplastic anemia as well as pure red cell aplasia, the MCV is normal: 80 to 100, again normal.
Siliconemia has three causes: acute blood loss, underproduction, over destruction. Aplastic anemia as well as pure red cell aplasia are in the same category. In aplastic anemia, the bone marrow has failed; pancytopenia. However, in pure red cell aplasia, only the red cell line is affected; white blood cells are normal; platelets are normal. So if only the red cell line is affected, we call this pure red cell aplasia. If these are affected, it's called a granulocytosis. If the platelets are affected, it's called thrombocytopenia with megakaryocytes. The "a" is close to the "m"; there is no space here, so it's megakaryocytes.
So what is pure red cell aplasia? One cell line only is compromised; the cell line is the RBC line. There is anemia and reticulocytopenia. Since all of the cell line is affected, not only the mature RBC's will be affected, but also the baby RBC's will be affected, and the precursors will be affected. It's very unlikely to progress to pancytopenia or anemia versus myelodysplastic syndrome, where there can be pancytopenia, or this is a mistake—leukemia. So in pure red cell aplasia, it's unlikely to progress to pancytopenia or leukemia. It's anemia, of course. So anemia is there; pancytopenia or leukemia are not there. Pathophysiology: maybe there are some destructive antibodies or lymphocytes; that's why it will respond very well to immunosuppressants. So keep that in mind.
Classification—that's a biggie. Pure red cell aplasia can be transient, such as transient erythroblastopenia of childhood, transient aplastic crisis of hemolysis. This is due to parvo B19. Fetal, such as hydrops fetalis. This is the non-immune type. Parvo B19, hereditary, such as Diamond-Blackfan syndrome. Acquired: thymoma. Viruses can be parvo B19, Epstein-Barr, human T-cell leukemia virus. Connective tissue diseases: lupus, rheumatoid arthritis, juvenile rheumatoid arthritis. Maybe some antibodies to EPO. EPO helps production of RBC's; there are antibodies to EPO; EPO cannot function, and then RBC's will be affected. Drugs such as phenytoin, procainamide, ionized; it is a thyroid print. If we do not know the reason, we call it idiopathic. Pay attention: parvo B19, parvo B19, parvo B19—it's a big deal. Quick question: is parvo B19 a DNA virus or an RNA virus? Please let me know down in the comments.
Diagnosis: on CBC, you will get low hemoglobin, low hematocrit, and low RBC count, why? Cuz it's anemia. Reticulocyte count or reticulocyte index is decreased. Why is that? The bone marrow has failed completely, no, only the red cell line. So reticulocytes, the baby RBC's, are decreased. Bone marrow biopsy will show you red cell aplasia plus giant pronormoblasts. Okay, so when we go from these myeloid stem cells down to the red blood cells, here is like a group of cells called pronormoblasts; they will be giant, present there. Why? Because they cannot progress to the small, mature RBC's; so they are stuck there, these big cells, and the RBC's are kind of absent. The baby RBC's, the reticulocytes, are also absent, but these pronormoblasts are present and abundant. DNA testing—this is the most accurate test: PCR for DNA of parvovirus B19. So if the exam asks you, "What's the best initial test?" Answer: reticulocyte count or index; it will be decreased. What's the most accurate test? DNA testing.
So let's have a case study here. I'll give you a second to read it; you can pause if you wish. Main things here: patient with sickle cell anemia, extremely tired, hematocrit dropped severely, reticulocyte index is low. Wow, that's very strange. Why? Sickle cell anemia patients are supposed to have a high reticulocyte index. So what happened? Maybe the factory that produces reticulocytes is damaged. You mean the bone marrow? Absolutely. White blood cells and platelets are within normal range, so it's pure; okay, only red blood cells are affected: red cell aplasia, most probably due to parvo B19. Why do you say parvo B19? Why not any other cause? Because there is sickle cell anemia. Parvo B19 is notorious in causing transient aplastic anemia if the patient previously had sickle cell anemia. So parvo B19, that's the most likely diagnosis. What's the most accurate diagnostic test? Most accurate test is PCR for DNA.
How to treat this parvo B19? Let's see treatment: treat the underlying cause. For example, if it's a drug, discontinue the drug. If there is a thymoma, remove the thymoma. If you have anemia, you can give RBC's, why? Because they are deficient. And when we give RBC's or blood, we do iron chelation because RBC's or blood has a lot of iron that will cause secondary hemochromatosis. So we chelate because iron is dangerous; of course you know that—transfusion reaction. If there is parvo, IVIG; it inhibits the macrophage. Steroids and immunosuppressants for idiopathic cases. Remember I told you the mechanism or the pathophysiology involved antibodies and some lymphocytes; so steroids and immunosuppressants will take care of that. That was the story of pure red cell aplasia. Do not forget: pure red cell aplasia, parvo, only the red blood cells, reticulocytes are decreased; most accurate test is PCR for DNA of this parvo B19. I'll see you in the next video. Take care. Bye-bye.