Haemolytic Anaemia Flashcards
1
Q
What is haemolytic anaemia?
A
Anaemia related to reduced RBC lifespan (no blood loss or haematological deficiency)
2
Q
What blood results would you see in haemolytic anaemia?
A
- decrease in Hb (due to haemolysis)
- increase in reticulocytes (bone marrow trying to replace red cells)
- increased bilirubin (product of haem breakdown)
3
Q
What are the types of congenital haemolytic anaemias?
A
- Abnormalities of RBC membrane (eg. hereditary spherocytosis)
- Haemoglobinopathies (eg. Thalassaemia)
- Abnormalities of RBC enzymes (pyruvate kinase deficiency/glucose 6 phosphate dehydrogenase deficiency)
4
Q
Describe features of hereditary spherocytosis
A
- AD inheritance
- red cells are polychromatic and spherocytic
- causes jaundice and splenomegaly
- treatment is splenectomy + hyposplenic prophylaxis (increases red cell lifespan and improves anaemia)
5
Q
Describe the mechanism behind pyruvate kinase deficiency
A
- pyruvate kinase is required for the finals step in glycolysis to produce pyruvate and ATP
- deficiency results in ATP depletion and extra-vascular haemolytic anaemia
- AR inherited
6
Q
Describe the mechanism behind glucose 6 phosphate dehydrogenase deficiency
A
- glucose 6 phosphate dehydrogenase is required for the conversion of NADP to NADPH to prevent the cell against oxidative damage
- deficiency results in acute episodes of intravascular haemolysis (triggered by oxidative stress eg. Eating fava beans, drugs - anti malarials, sulphonamides etc.)
- X-linked recessive inherited
7
Q
What are the types of acquired haemolytic anaemia?
A
- autoimmune (warm type/cold type/drug induced)
- isoimmune (haemolytic disease of the newborn)
- non-immune (fragmentation haemolysis)
8
Q
Describe warm type autoimmune haemolytic anaemia
A
- IgG mediated
- causes: idiopathic, autoimmune disease, lymphoproliferative disease, drug induced
- causes spherocytic polychromatic cells
- treatment: stop any drugs, give steroids, immunosuppressants, splenectomy
9
Q
Describe cold type autoimmune haemolytic anaemia
A
- IgM mediated
- causes: mycoplasma infection, idiopathic, lymphoproliferative disorders
- causes big red cells that stick together
- blood film shows agglutination
- treatment: self limiting if mycoplasma infection, if idiopathic keep warm
10
Q
Describe the different mechanisms of drug induced autoimmune haemolytic anaemia
A
- drug binds to red cell and together raise levels of autoantibodies (usually mild)
- drug can activate autoantibodies to bind to them and the red cells activating the complement system (severe eg. Cephalosporins)
- drug itself activates autoantibodies against red cells (mild)
11
Q
Describe the direct Coombs test
A
- detects antibodies on the surface of red cells
- anti-human immunoglobulin is added which forms a lattice with autoantibodies on the surface of red cells and agglutinate
- a positive test means it is autoimmune haemolytic anaemia or haemolytic disease of the newborn
12
Q
Describe the indirect Coombs test
A
- detects antibodies in patient plasma
- patient’s plasma is added to a sample of red cells, if the patient has antibodies present it will bind to the red cells and agglutinate
- used in pregnancy to see if maternal plasma contains antibodies against foetal red cells
13
Q
Describe haemolytic disease of the newborn (HDN)
A
- when a rhesus negative mother is pregnant with a rhesus positive foetus
- during pregnancy some foetal red cells will leak into maternal circulation
- mother will generate antibodies against foetal cells which are IgG and able to cross placenta into foetal circulation
- these can bind to and attack foetal red cells resulting in haemolysis
- in first pregnancy just immunises mother, in second pregnancy usually causes haemolysis
14
Q
Describe fragmentation haemolysis
A
- blood film shows red cell fragments and target cells (codocytes)
- causes: haemolytic uremic syndrome and thrombolytic thrombocytopenia (neuro symptoms)
