Disorders of erythrocytes

image of Disorders of erythrocytes
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Erythrocyte disorders fall into two broad groups: anaemia; and erythocytosis (or polycythaemia). Anaemia may be due to reduced or defective red cell production, which results in non-regenerative anaemia, or increased red cell loss, which results in regenerative anaemia. This chapter looks at the following: A review of erythropoiesis, anaemia, erythocytosis and blood typing. Case examples are included.

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4.1 Erythropoiesis. The developing red cell precursors become progressively smaller and accumulate haemoglobin. They are released into the circulation as reticulocytes which then develop into mature red cells. Drawn by S.J. Elmhurst BA Hons (www.livingart.org.uk) and reproduced with her permission.
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4.2 Stages of erythropoiesis shown on a bone marrow aspirate. MR = metarubricyte; PRC = prorubricyte; RB = rubriblast; RC = rubricyte. (Modified Wright–Giemsa stain; original magnification X1000)
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4.3 Blood film from a dog with regenerative anaemia due to blood loss. There is marked polychromasia (darker purple cells, bottom arrow). Target cells (codocytes) are present (top arrow); these have a wide area of central pallor within which there is a central circular density of haemoglobin. (May–Grünwald–Giemsa stain; original magnification X1000)
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4.4 Diagrammatic representation of the structure of haemoglobin, with four haem rings connected by globin chains.
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4.7 A histogram showing red cell size on the -axis and cell number () on the -axis, from a dog with regenerative anaemia. There is a ‘hump’ to the right of the main peak (arrowed) indicating increased numbers of large red cells.
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4.8 Red cell dot plot generated by the Advia 120 analyser. Haemoglobin concentration is on the -axis and cell size on the -axis. Cells within the central box are normocytic and normochromic (white arrow). In regenerative anaemia a cloud of cells is found in the upper left box corresponding to macrocytic hypochromic cells (black arrow).
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4.9 Scatter plot from a Procyte Dx analyser showing the red cell plot from (a) a normal dog and (b) a dog with regenerative anaemia. The reticulocytes take up a dye which, on encountering laser light, emits fluorescent light. The platelet cloud (in blue) appears below the red cell cloud. (Courtesy of G Bilborough, Idexx)
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4.10 Appearance of reticulocytes on a blood film stained with new methylene blue. (a) In the dog, reticulocytes have numerous dark-staining aggregates. (b) In the cat, aggregate reticulocytes have large clumps of ribosomes (black arrows), while punctate reticulocytes have a few small inclusions (white arrows). (New methylene blue stain; original magnification X1000)
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4.12 The effect of degree of anaemia on uncorrected reticulocyte percentage. The proportions of mature red cells and reticulocytes are shown schematically in red and black, respectively. The normal animal on the left has a low percentage of reticulocytes. In the animals with mild and severe anaemia, the same absolute number of reticulocytes is circulating, but the reticulocyte percentage is higher in severe anaemia because there are fewer mature cells. This gives a false impression that the severe anaemia is more regenerative than the mild anaemia.
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4.15 Features of a regenerative anaemia. There are polychromatic macrocytic red cells corresponding to reticulocytes (P), cells containing a Howell–Jolly body (H) and nucleated red cells (N). In this case the anaemia was due to immune-mediated haemolysis and there are numerous spherocytes (S). (Modified Wright’s stain; original magnification X1000)
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4.16 Blood smear from an 8-year-old German Shepherd Dog with a splenic mass, showing schistocytes (black arrows) and acanthocytes (white arrow). (Modified Wright’s stain; original magnification X1000)
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4.17 Poikilocytes, their appearance and causes. DIC = disseminated intravascular coagulation.
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4.18 Hypochromic red cells (1), normochromic red cells (2) and fragmented red cells (3) from a dog with iron-deficiency anaemia. (Modified Wright’s stain; original magnification X1000)
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4.19 Red cell cytogram from an Advia 120 analyser for a dog with iron-deficiency anaemia. There are two populations of cells: one is normocytic/normochromic (these cells were produced prior to the onset of iron deficiency) and one is microcytic/hypochromic (arrowed).
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4.21 Extravascular haemolysis. Antibody Fc receptors on macrophages bind to the antibody on the red cell surface, leading to phagocytosis of the red cell. Phagocytosis of a portion of the red cell membrane leads to the formation of a spherocyte.
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4.22 Blood film from a 4-year-old female Cocker Spaniel with immune-mediated haemolytic anaemia. Numerous spherocytes are seen, which are smaller and denser than normal red cells and lack central pallor. There are two nucleated red cells and two monocytes. (May–Grünwald–Giemsa stain; original magnification X1000)
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4.23 Intravascular haemolysis. Large amounts of antibody on the red cell surface lead to complement fixation, damage to the red cell membrane and movement of water into the cell, causing swelling and lysis.
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4.24 (a) Gross appearance of autoagglutination after mixing an equal volume of blood and saline on a slide. This should be confirmed by saline washing (see text) and examined microscopically. (b) Microscopic appearance of red cell agglutination with large irregular clumps of red cells. (Unstained cells; original magnification X400 with condenser lowered) (c) Rouleaux are long chains of stacks of red cells (Unstained cells; original magnification X400)
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4.26 Coombs’ test. (a) Antibody directed against IgM, IgG and complement is incubated with the patient’s washed red cells. The antiglobulin binds to the antibodies/complement on the red cells, resulting in agglutination. (b) The test is performed on a microtitre plate, with progressively more dilute antiglobulin. In a positive test, small clumps of red cells remain suspended in the well; in a negative test the red cells sink to the bottom of the well, forming a button. (c) A positive DAT result using an immunochromatographic strip method.
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4.27 Blood smear (Wright’s stain) from a cat with asymptomatic infection with M. haemominutum. Arrows indicate individual organisms. (Courtesy of S Tasker)
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4.28 Blood film from a dog with babesiosis. Paired organisms are seen. (May–Grünwald–Giemsa stain; original magnification X1000)
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4.29 Blood films from a cat with hepatic lipidosis and anaemia. (a) There are frequent Heinz bodies (lighter-staining circular bodies) seen within and protruding from the surface of the red cells (arrowed). A Howell–Jolly body is labelled H. (Modified Wright’s stain; original magnification X1000) (b) On a smear stained with new methylene blue, the Heinz bodies are obvious dark-staining round bodies. (Original magnification X1000) (a, Courtesy of P Monti)
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4.30 Blood film from a dog with zinc toxicity, showing large numbers of eccentrocytes with haemoglobin shifted to one side of the cell, leaving the other side clear. (Wright’s stain; original magnification X1000) (Courtesy of D DeNicola)
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4.32 Bone marrow aspirate from a dog with non-regenerative IMHA showing marked erythroid hyperplasia. There is a marked predominance of erythroid precursors at all stages of maturation with only occasional myeloid cells. (Modified Wright–Giemsa stain; original magnification X1000)
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4.33 Bone marrow aspirate from a dog with stage V lymphoma. There is a predominance of large lymphoid cells with only occasional myeloid and erythroid precursors. (Modified Wright–Giemsa stain; original magnification X1000)
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4.34 Bone marrow core biopsy sample from a dog with myelofibrosis. There is trabecular bone (B) with haemopoietic spaces containing haemopoietic tissue (H) and streaming fibrous tissue (F). (Haematoxylin and eosin stain; original magnification X200)
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4.36 Bone marrow aspiration. (a) Aspiration from the greater tubercle of the humerus. Bone marrow aspiration. (b) Drops of marrow are placed at the top of the tilted slide, allowing blood to run off to the bottom of the slide but retaining the spicules. (c) Smears are made by placing a second slide over the first, thus spreading the spicules, and then smoothly drawing the slides apart.
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4.37 A good quality bone marrow aspirate. The smear is very cellular and cells have spread into a monolayer without clotting. Three megakaryocytes are present, with large multilobulated nuclei. (May–Grünwald–Giemsa stain; original magnification X1000)
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4.38 Blood film from a dog with severe anaemia. (Wright–Giemsa stain; original magnification X1000)
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4.39 Blood film from a dog with severe non-regenerative anaemia. (Wright–Giemsa stain; original magnification X1000)
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