Erythrocytes (anaemia) Flashcards
what is the difference between regenerative and non-regenerative anaemia?
Regenerative anaemia: RBC production is normal, but they are being destroyed
Non-regenerative anaemia: there is an issue with haematopoiesis
what indicator is used to tell if the anaemia is regenerative or non-regenerative?
reticulocytes in the blood smear
Reticulocytes are the stage of maturation right before erythrocytes, and they appear bigger and bluer due to the presence of residual RNA.
Therefore, their presence indicates regenerative anaemia.
what are the two types of non-regenerative anaemia?
- nutrient deficiencies
- bone marrow and erythroid hyperplasia/aplasia causes reduced erythropoiesis
what is the most common nutrient deficiency?
iron
causes of iron deficiencies
inadequate dietary intake intake (uncommon in dogs and cats, only in piglets and calves, as they are selected to grow really fast (iron in milk cannot compensate) and they usually have concrete floors – no access to soil which is a big source of iron.
Chronic external blood loss – GIT ulcers, blood-sucking parasites, fleas and ticks
Anaemia of inflammatory disease (chronic) – due to over-secretion of hepcidin, overall iron content is normal but it’s all being shifted into storage
what are the roles of transferrin, ferritin and hepcidin
Transferrin = plasma protein for iron transport
Ferritin = storage of iron into macrophages (spleen, liver, bone marrow)
Hepcidin = protein secreted by hepatocytes and is the main systemic regulator of iron metabolism – causes iron to be put into storage
what might you see in a blood smear that is indicative of an iron deficiency?
leptocytes (RBCs with dark ring outside and pale inside) - super specific to iron deficiency
codocytes (target cells)- less specific
causes of reduced erythropoiesis
- EPO deficiency
- anaemia of inflammatory disease
- immune-mediated anaemia
- pure red cell aplasia
- abnormalities in heme synthesis
EPO deficiency
(EPO = erythropoietin)
Very common, EPO is the only hormone able to stimulate erythrocyte production
EPO is produced by the kidneys – chronic renal disease can lead to this
-> mild to moderate, non-regenerative, normocytic, normochromic anaemia
anaemia of inflammatory disease
1) iron deficiency – large amount of iron is stored within macrophages during inflammation, as a protective mechanisms to hide the iron from the infectious agents
2) shortened erythrocyte lifespan – due to membrane damage caused by endogenous oxidants
3) inhibition of erythropoiesis – secondary to inflammatory mediators
-> mild to moderate, non-regenerative, normocytic, normochromic anaemia
immune-mediated anaemia
Antibody or cell-mediated response against maturation antigens on nucleated erythrocyte precursors (maturation arrest) and/or reticulocytes (marrow hyperplasia)
-> moderate to severe, non-regenerative, normocytic, normochromic anaemia
pure red cell aplasia
Suppression of erythroid burst-forming units – only erythrocytes affected
Dog: immune-mediated, immune response to recombinant human EPO
Cat: FeLV subgroup C infections
-> severe, non-regenerative, normocytic, normochromic anaemia
abnormalities in heme synthesis
Iron and copper deficiency, lead toxicity
-> mild to moderate, non-regenerative, normocytic, normochromic anaemia with basophilic stippling and nucleated RBCs
causes of regenerative anaemia
blood loss
increased erythrocyte destruction (haemolysis)
acute blood loss anaemia
trauma, coagulation disorders (DIC, rodenticide toxicity), platelet disorders
Rapid loss of more than 20-30% blood volume = hypovolaemic shock and death
Rapid loss of up to 20% blood volume =
- Immediately after: hypovolaemia without anaemia (balanced loss of RBCs and plasma)
- After several hours: normovolaemia (due to compensatory mechanisms), pre-regenerative, normocytic, normochromic anaemia, thrombocytosis, hypoproteinaemia
- After 3-4 days: regenerative, macrocytic, hypochromic anaemia
chronic blood loss anaemia
parasites, GIT ulcers, neoplasia
main cause of iron deficiency anaemia
intravascular vs extravascular haemolysis
intra = RBCs are destroyed whilst in the peripheral blood, results in haemoglobinaemia, haemoglobinuria, icterus
extra = phagocytosis by cells of the mononuclear phagocyte system (macrophages in the spleen, liver and bone marrow)
IMHA
destruction of erythrocytes induced by the production of antibodies that target erythrocytes
very common in dogs, rare in cats and large animals
80% of cases are extravascular
clinical blood changes associated with IMHA
severe regenerative or pre-regenerative, macrocytic and hypochromic anaemia, hyperbilirubinaemia, leukocytosis
neonatal isoerythrolysis
An IMHA that develops in neonatal animals following ingestion of colostrum containing antibodies against antigens on their erythrocytes. Only in horses and cats.
transfusion reactions
Occur when plasma of the recipient contains antibodies against one or more of the antigens on the surface of the donor erythrocytes.
drug-induced IMHA
Penicillin (horses), cephalosporins (dogs), levamisole (dogs) etc.
Slow progression – need prolonged administration of the drug
oxidative compounds
e.g. paracetamol in cats, onions/garlic in dogs etc.
blood smear changes with oxidative compounds
heinz bodies - blebs protruding from the RBC membrane (product of oxidised haemoglobin)
eccentrocytes - eccentric pallor of RBCs, caused by oxidation of lipids (less common than heinz bodies)
