Red Cell Disorders – Diseases of the Blood System

by Paul Moss, PhD

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    00:01 Hello, in this lecture, I'd like to introduce you to the range of diseases that can be seen within the blood system.

    00:07 The outcomes that we'll get from this lecture are quite wide ranging.

    00:12 You'll see that there are many types of disorder that can arise from the blood system and the good way to approach these is to break them down into three different areas: red cells, white cells and disorders of blood clotting which will include platelets and the coagulation factors.

    00:32 We'll see that red cell problems are dominated by anaemia, for which there are many causes.

    00:39 The most important disorders related to white cells are leukaemia and lymphoma and I'll introduce those to you.

    00:47 Finally, platelet disorders and coagulation problems and very different patterns of bleeding and we'll discuss the major causes of these disorders.

    00:58 Let's start with red cells.

    01:00 On the right there you'll see a very beautiful picture of the red cells.

    01:05 Now if there is a reduction in the number of red cells or the haemoglobin concentration in the blood, this is called ANAEMIA. This is a very common disorder and the body becomes deprived of oxygen because of course the major function of red cells is to carry oxygen to the tissues.

    01:25 So the sort of clinical problems that the patient develops are tiredness, shortness of breath, perhaps problems in concentration. Now anaemia may arise because of a decrease in the production of red cells or an increase in the destruction or loss of these cells.

    01:45 Let me try and classify that for you in another way.

    01:50 So here you'll see a diagram showing decreased production of red cells and how that may occur.

    01:57 And at the top in dark green, you'll see 3 categories and in the middle, reduced bone marrow erythroid activity due to problems with general bone marrow function, aplastic anaemia or leukaemia.

    02:11 On the right, you'll see ineffective red cell formation due to disorders such as inflammation and on the other side, you'll see nutritional deficiencies: iron, vitamin B12 deficiency and you'll see that all of those feed down into a failure of production of the red cells by the bone marrow On the left of the bottom line, you will see two causes of loss or destruction of red cells - bleeding or increased destruction through hemolysis. And finally on the right hand side, an unusual cause of anaemia, which is where it's just apparent because of dilution of the red cells by an increased plasma volume. Let's look at this in a little more detail, particularly on the decreased production of red cells.

    03:00 As a key factor here to remember,you may get a decreased production of red cells because of a complete bone marrow failure. Now, in that case, all the blood cells in the blood will be reduced, the white cells and the platelets, so its normally quite apparent. All the reduction in red cell production can be specific, just the red cells and that can be due to factors such as nutritional deficiency of iron and vitamins which are needed for hemopoiesis. It can occur through inherited disorders of haemoglobin or due to chronic diseases or kidney problems. We will discuss these in a little more detail.

    03:47 Now one useful approach for trying to sort out these different sorts of anaemias is the size of the red cell.

    04:00 You will see along the top there in blue. The anaemia type can be classified into those three groups: (1) microcytic and hypochromic disorders. What does that mean? Microcytic - small red cells, hypochromic - a reduction in the amount of haemoglobin. So they don't stain as well on the blood film.

    04:21 That's one major classification. If we follow that line down, you will see that the red cell indices show that the MCV and the MCH - that means the mean cell volume and the mean cell haemoglobin are both low.

    04:38 You'll see at the bottom, iron deficiency and thalassaemia as the causes. I'll address that in a minute.

    04:46 In the middle section, (2) normocytic, normochromic- normal size, normal amount of haemoglobin.

    04:52 You'll see there that the red cells indices are normal and at the bottom, a range of possible causes: blood loss, hemolysis, chronic disease or marrow infiltration.

    05:04 And on final section, (3) macrocytic disorders. You will see here the MCV and MCH were actually increased.

    05:13 These are big red cells carrying more haemoglobin, and the major cause is a megaloblastic anaemia.

    05:21 Let's look at that in a little more detail. Microcytic red cells are seen in two major disorders.

    05:29 That's the key point to remember, two major diagnoses, of which iron deficiency is the more common.

    05:39 Thalassaemia is the other major disorder and that's an imbalance in the production of the globin chains - alpha and beta.

    05:50 Normocytic red cells, normal sized red cells observed in disorders of the bone marrow, inflammatory diseases or where the kidney is not functioning properly,renal disorders and that is due to a reduction in erythropoietin production.

    06:06 Finally, large red cells, macrocytic red cells are a feature of vitamin deficiencies particularly vitamin B12 and folic acid. I shall also mention hemolysis here, hemolytic disorders where red cells are being destroyed. They are normally normocytic but they can be occasionally macrocytic because young red cells- reticulocytes are slightly larger than red cells and they may just push the MCV up just a little into the macrocytic range.

    06:38 Now the opposite of anaemia is polycythaemia. That's when you have too many red cells in your blood.

    06:49 This can cause problem because the blood gets very thick, very viscous and it gets quite hard for the heart to pump this thick blood around the body and they can also increase the risk of thrombosis, blood clotting.

    07:04 That's quite a serious concern. Now polycythaemia can be a natural response of the body trying to adapt to hypoxia - reduction in oxygen tension and this can occur quite commonly in people who smoke heavily, who have lung problems or indeed live perhaps at high altitude.

    07:27 Now here we see the body trying to respond to this hypoxia by increasing erythropoietin (EPO) If we took a blood test from these patients,we would see that the erythropoietin level is high.

    07:40 This can also occur in patients who develop a clonal expansion of red cell precursors in the bone marrow called Polycythaemia Vera and here erythropoietin level is normal or reduced.

    07:55 The bone marrow is essentially out of control. It's not responding to erythropoietin.

    08:00 It is growing autonomously, on its own producing too many red cells.

    08:06 You will see on the right-hand side a slide I wonder if you can associate this with polycythaemia.

    08:15 If you notice carefully the patient here has nails which are just slightly blue, cyanotic as we call it, the patient is hypoxic. You may also notice that the patient's nails are clubbed and they're very rounded.

    08:28 This is a patient who had a long standing heart defect leading to cyanotic problems with the blood and that can lead to very thick blood, very high haemoglobins because of increased levels of erythropoietin.

    About the Lecture

    The lecture Red Cell Disorders – Diseases of the Blood System by Paul Moss, PhD is from the course Hematology: Basics.

    Author of lecture Red Cell Disorders – Diseases of the Blood System

     Paul Moss, PhD

    Paul Moss, PhD

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