Immune mediated haemolytic anaemia in the dog workshop Flashcards
How could immune mediated haemolytic anaemia cause pyrexia?
Antigen-antibody complexes are a powerful stimulus for release of cytokines and activation of complement. Pro inflammatory cytokines in the circulation can act at the level of the hypothalamus to alter the set point for body temperature regulation
Pyrexia could also indicate an underlying infectious disease as a trigger factor for IMHA
How could immune mediated haemolytic anaemia cause pale MMs?
Anaemia
Poor peripheral perfusion
How could immune mediated haemolytic anaemia cause jaundice?
Haemolytic jaundice: Haemolysis (excessive break down of red blood cells) overwhelms the liver’s ability to process break down products from haemoglobin and leads to accumulation of bilirubin
How could immune mediated haemolytic anaemia cause lymphadenopathy (enlarged lymph nodes)?
Associated with activation of the immune response
How could immune mediated haemolytic anaemia cause splenomegaly?
Site of phagocytosis of opsonised red blood cells (ie red blood cells bound to circulating antibody and/or complement) by macrophages.
Splenomegaly could also occur because the spleen is a site of secondary haematopoiesis activated in response to anaemia
How could immune mediated haemolytic anaemia cause tachycardia?
Reduced oxygen carrying capacity leads to increased heart rate to increase cardiac output
Could also be related to impact of inflammatory cytokines
How could immune mediated haemolytic anaemia cause tachypnoea?
Reduced oxygen carrying capacity can lead to increased respiratory rate
How do these results help rule our blood loss as the cause of anaemia?
PCV is low and is consistent with significant anaemia
Total solids is normal - would usually be reduced together with PCV in blood loss anaemia
What are the markers on a blood smear that suggest an anaemia is regenerative?
Polychromasia – immature red blood cells
Anisocytosis – variable red cell sizes (immature red cells tend to be larger than mature red cells)
Increased nucleated red blood cells
Identify P, S and NE on this blood smear
P = large polychromatic red blood cells likely reticulocytes (immature red blood cells)
NE = nucleated erythrocyte
S = spherocytes
What haematology markers suggest an anaemia is regenerative?
MCV (high if regenerative)
Reticulocyte count (high if regenerative)
MCHC: low
What are spherocytes and when are they found?
smaller and rounder/denser than normal red blood cells (no central pallor seen in spherocytes).
Fragments of red blood cells that result from damage by partial phagocytosis by macrophages in the spleen and/or liver.
What tests can be done to look for evidence of an extreme type II hypersensitivity response?
Evidence of autoagglutination
In saline agglutination test
Coombs test (if in saline test is negative)
Describe the evidence of autoagglutination in haematology
IgM or IgG auto antibodies attach to antigens on the surface of red blood cells and draw together red blood cells causing clumping known as autoagglutination
Appreciated as speckles which can accumulate on the surface of the blood tube (EDTA is the best anticoagulant to use) and are seen when it is tipped gently
Not the same as blood clots which are much larger
Describe the in saline agglutination test
1 drop of EDTA blood with 4 drops of saline on a slide. Mix and examine under a microscope.
Important to differentiate agglutination (clusters of grapes) due to high antibody levels from rouleaux (stacks of coins)
describe the coombs test
A direct antiglobulin test
an agglutination test used to detect the presence of immunoglobulins (auto antibody) and/or complement on the surface of red blood cells in dogs with IMHA
What are the possible mechanisms of IMHA causing damage to RBCs?
What is primary and secondary IMHA?
Primary IMHA is also known as idiopathic IMHA ie this occurs spontaneously likely associated with an underlying genetic and/or environmental predisposition
Secondary IMHA occurs when underlying disease acts as a trigger factor activating the immune system and directing attack on the red blood cells
How is primary IMHA treated?
- Treatment of primary IMHA is focused on supportive care and halting the inappropriate immune response with immune suppressive treatment
How is secondary IMHA treated?
treatment should focus on the underlying cause
