ERYTHROCYTE (RBC) DISORDERS: POLYCYTHAEMIA AND ANAEMIA Haematology ERYTHROCYTE (RBC) DISORDERS: POLYCYTHAEMIA AND ANAEMIA

OVERVIEW 1. Polycythaemia (erythrocytosis) 2. Anaemia -Regenerative: blood-loss or haemolytic -Non-regenerative: primary or secondary bone marrow disorder

1.POLYCYTHAEMIA/ ERYTHROCYTOSIS

DEFINITION AND TYPES An increase in PCV, Hb concentration and/or RBC count Relative • Dehydration (eg. increased water loss: e.g. vomiting, diarrhoea, polyuric disorders) causing an apparent increase in RBC due to a decrease in fluid in circulation. • Exercise, fear, excitement (eg. in the horse) causing adrenaline secretion, splenic contraction and transient redistribution of RBC from the spleen to the circulation.

DEFINITION AND TYPES Absolute (real increase in RBCs) • Secondary: - chronic tissue hypoxia: heart/lung diseases, high altitude - renal tumor or cysts increasing erythropietin (EPO) secretion • Primary: - polycythaemia vera (rare myeloproliferative disorder of RBC precursors)

CLINICAL IMPLICATIONS -Cardiovascular signs due to blood hyperviscosity and peripheral hypoxia (increased pulse and respiratory rate) -Neurological signs (syncope, lethargy) due to poor brain perfusion, and bleeding tendencies

LABORATORY DIAGNOSIS OF DIFFERENT CAUSES Relative • Dehydration: total protein and albumin Absolute • Secondary to chronic hypoxia: arterial pO2 • Renal tumours or cysts (or others): erythropoietin EPO*) • Polycythaemia vera: EPO *Human immunoassays kits should be validated prior to use for measurement of canine and feline erythropoietin

2. ANAEMIA

Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic haemorrhagic Anaemia secondary B-M disorders B-M (bone-marrow) non regenerative primary B-M disorders

ANAEMIA A decrease in PCV, Hb concentration and/or RBC count Low PCV

ANAEMIA: CLINICAL IMPLICATIONS - Inadequate tissue oxygenation • pale mucous membranes • weakness, inappetance, anorexia • syncope - Compensatory mechanisms • tachypnoea (particularly if forced to exercise) • tachycardia, small and strong pulse

ANAEMIA: CLINICAL IMPLICATIONS -Signs which may be associated with cause of anaemia • icterus • bleeding (petechiae,ecchymoses, melena, haematuria, haematomas) • fever • splenomegaly

Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic haemorrhagic Anaemia secondary BM disorders B-M (bone-marrow) non regenerative primary B-M disorders

REGENERATIVE ANAEMIA Characterized by an increase in the number of RETICULOCYTES produced by the bone marrow to compensate for the anaemia.

SIGNS OF REGENERATIVE ANAEMIA Reticulocytosis will produce: -  MCV and RDW,  MCH and MCHC - In blood smears with Romanowsky stains: • polychromasia • anisocytosis See lecture 4 for abreviations. Additionally it can be found: -increased nucleated RBCs -basophilic stippling -increased number of Howell-Jolly Bodies Secondary effects may include: -leukocytosis with neutrophilia and left shift -thrombocytosis

Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic haemorrhagic Anaemia secondary BM disorders B-M (bone-marrow) non regenerative primary B-M disorders

HAEMORRHAGIC ANAEMIA Plasma total protein generally  (because protein is lost together with RBC) Plasma clear If measured in the aftermath of the loss of a lot of blood and before blood volume is restored, RBCs values and plasma protein may appear within reference ranges.

HAEMORRHAGIC (blood-loss) ANAEMIA ACUTE BLOOD LOSS Reticulocyte response will only be detected in blood after 3-4 days !! Causes: • Trauma, surgery • Coagulation disorders • Others There are many others causes of acute blood loss such as: - abomasal or intestinal ulceration - severe angiostrongylus infestaion - rupture of haemangiosarcomatous spleen Reticulocytes does not appear in peripheral blood in all species. Acute blood loss can cause hypotension and shock (due to severe hypovolaemia)

• Gastrointestinal ulceration and tumours • Parasitism CHRONIC BLOOD LOSS - External. Causes: • Gastrointestinal ulceration and tumours • Parasitism In many cases signs of RBC regeneration are present in blood but progressive depletion of iron stores may produce IRON DEFIENCY ANAEMIA with: -normo to microcytosis -hypochromasia - ↑ platelet count -reticulocytes can decrease Examples of gastrointestinal tumours: carcinoma/leiomyosarcoma Parasitism can be internal or external - Internal : blood loss into abdomen/chest

IRON DEFICIENCY ANAEMIA An increased number of platelets, and hypochromic and microcytic RBCs can be observed in the blood smear

Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic haemorrhagic Anaemia secondary B-M disorders B-M (bone-marrow) non regenerative primary B-M disorders

HAEMOLYTIC ANAEMIA Plasma total protein within reference range or  Plasma can be icteric or hemolysed Abnormal erythrocyte morphology (Heinz bodies, RBC parasites, spherocytes) may suggest a haemolytic cause for the anaemia In haemolytic anaemia the plasma frequently appears yellow (“icteric” or “jaundiced”) due to increased RBC destruction and increased bilirubin metabolism (mostly unconjugated). In severe haemolysis, haemoglobinaemia (producing red colour in plasma) and haemoglobinuria (producing red colour in urine) may result from the body´s inability to bind Hb to haptoglobin, and the inability of the monocyte macrophage system to metabolise amounts of Hb being released.

IN REGENERATIVE ANAEMIAS: TPP and plasma colour can be used to differentiate haemolysis and haemorrhage Haemolytic anaemia Haemorrhagic anaemia TPP > 60 g/L PLASMA ICTERIC/ HEMOLYSED TPP < 60 g/L PLASMA CLEAR RBC regeneration following haemolysis is usually much more marked than that following blood loss.

Clinical signs associated with an increase in haemoglobin HAEMOLYTIC ANAEMIA Clinical signs associated with an increase in haemoglobin catabolism: • Haemoglobinemia and haemoglobinuria • Icterus Icteric serum when serum bilirubin levels >20mol/L Icteric tissues when serum bilirubin levels >50mol/L

HAEMOLYTIC ANAEMIA Red blood cell lysis may occur by two mechanisms: 1. INTRAVASCULAR HAEMOLYSIS 2. EXTRAVASCULAR HAEMOLYSIS

INTRAVASCULAR HAEMOLYSIS (causes) -Parasites/infectious causes Vascular Endothelial Lesions Oxidant damage - Others Parasites/infectious causes: Babesia, Mycoplasma haemofelis, toxins (Leptospira, Clostridium). Vascular Endothelial Lesions: haemangiosarcomas, DIC?, splenic torsion, heartworm disease. Oxidant damage: vegetable, animal toxins and drugs (onions, snake venom, methylene blue, acetaminophen). Others:poisoning with Cu and Zn, genetic (pyruvate kinase/phosphofructokinase deficiency), severe hypophosphataemia

INTRAVASCULAR HAEMOLYSIS (laboratory findings) In addition to  PCV, TPP within the reference range or  and icteric/hemolysed plasma - Parasites/infectious causes: Blood smears, Serology/PCR Vascular Endothelial Lesions: Schistocytes in blood smears - Oxidant damage: Heinz bodies in blood smears

Heinz bodies Schistocyte

EXTRAVASCULAR HAEMOLYSIS -Physiological. (aged erythrocytes) removed by the macrophage-monocyte system in the spleen -Pathological. (Auto)antibodies are produced against “normal” erythrocytes that are phagocytosed by the spleen - INMUNE-MEDIATED HAEMOLYTIC ANAEMIA

INMUNE-MEDIATED HAEMOLYTIC ANAEMIA - Idiopathic (unknown mechanisms) - Secondary to: • Infectious agents • Drugs/insecticides/vaccines/neonatal isoerythrolysis CAUSE THE APPEARANCE OF ABNORMAL ANTIGENS ON THE ERYTHROCYTE CELL MEMBRANE

INMUNE-MEDIATED HAEMOLYTIC ANAEMIA (laboratory findings) In addition to  PCV, TPP = within the reference range or  and yellow coloured plasma Spherocytosis (canine blood) Autoagglutination Gross autoagglutination on a slide

Spherocytosis Autoagglutination

INMUNE-MEDIATED HAEMOLYTIC ANAEMIA: ADDITIONAL TESTS TO CHARACTERIZE INMUNE-MEDIATED HAEMOLYTIC ANAEMIA: COOMBS TEST - ERYTHROCYTE FRAGILITY TEST

COOMBS TEST Detects antibodies directed at the erythrocyte membrane Falses +´s: -some chronic infections - “ parasites (heartworms, haemobartonella) - “ drugs (trimethoprim-sulfa) - “ neoplasms Falses -´s: in some cases of inadequate antibody production Usually consists of antisera against IgG, IgM and C3 (complement), and detects the presence of these factors on RBC surface. Thrice-washed RBCs from the patient are mixed with antisera and a positive reaction is denoted by marked clumping of RBC. The test is species-specific

ERYTHROCYTE FRAGILITY TEST:BASIS Whole blood in a hypotonic solution (0.55% NaCl) Normal RBCs absorb water from the hypotonic solution for osmotic equilibrium and are distended but not haemolyzed Membranes of fragile RBCs (spherocytes, and those with enzyme deficiencies or damaged by some drugs) cannot withstand distension and are haemolyzed Spherocytes are small and dense, and do not have central pallor, so can be easily detected in canine blood smears since normal erythrocytes have central pallor. The erythrocyte fragility test can be a help for detecting spherocytes in species with erythrocytes without central pallor.

Anaemia regenerative non regenerative TYPES OF ANAEMIA haemolytic haemorrhagic Anaemia secondary B-M disorders B-M (bone-marrow) non regenerative primary B-M disorders

NON-REGENERATIVE ANAEMIA Characterized by an absence of, or reduction in reticulocyte response in an anaemic animal. This will produce: • Normocytic-normochromic anaemia MCV and RDW, MCH and MCHC within the reference ranges • In blood smears with Romanowsky stains: - absence of polychromasia and anisocytosis

NON REGENERATIVE ANAEMIA (causes) - Primary bone marrow disorders: some myeloproliferative, lymphoproliferative and myelodisplastic disorders virus (feline leukaemia/ canine parvovirus) some drugs: oestrogens, inmunosuppressive agents, non-steroid anti-inflammatories - Secondary: chronic inflammatory disease, some endocrine diseases chronic renal failure with decreased erythropoietin levels Other causes of primary bone marrow disorders can be mycotoxins and irradiation.

NON REGENERATIVE ANAEMIA (laboratory findings) In addition to  PCV and absent/reduced signs of RBC regeneration (reticulocytes) - Primary (bone marrow disorders): Diagnosis by bone marrow evaluation + specific tests. Leukopenia and/or thrombocytopenia may also occur - Secondary: Laboratory findings of the primary disease. (e.g. chronic renal failure:  BUN and creatinine)

- RBC loss or destruction has occurred within the previous 4 days NON REGENERATIVE BLOOD SMEARS MAY BE SEEN IN HAEMORRHAGE OR HAEMOLYSIS IF: - RBC loss or destruction has occurred within the previous 4 days - chronic haemorrhage has induced iron deficiency anaemia - animals with a low reticulocyte response: bovine, and particularly equine species. In the latter, the only sign that regeneration is occurring may be a small increase in MCV. In these cases serial haemograms are highly recommended

CLASSIFICATION OF ANAEMIAS BASED ON RBC INDICES - Macrocytic-hypochromic (regenerative) - Normocytic-normochromic (non regenerative) - Microcytic-hypochromic or normochromic (iron deficiency) * Macrocytic-hypochromic anaemias are usually produced by the presence of reticulocytes and it is a sign of regeneration. However, there are other causes of macrocytic RBCs which are not associated with regenerative anaemias: - FeLV - Vit B12 and folic acid deficiency - Chemotherapy (eg. With methotrexate) * Lead intoxication can produce microcytic RBCs and the appearance of nucleated RBCs

DIAGNOSIS OF ANAEMIAS: SUGGESTED APPROACH The following questions must be addressed: 1. Regenerative or non-regenerative? 2. If regenerative: haemolytic or haemorrhagic? 3. If non-regenerative: primary or secondary bone marrow disorder?