Session 5- Haemolytic Anaemia And Haemoglobinopathies Flashcards
What is the physiological life cycle of a red blood cell?
Red blood cells are produced in the bone marrow by erythropoiesis and haemoglobin synthesis also occurs here. Then peripheral red blood cells mature and develop function/structure and metabolism. Red blood cells are then removed by the reticulocytes- endothelial system.
What two types of anaemia may result from mutations in the genes that encode the globin proteins?
Thalassaemia and sickle cell diseases.
What is thalassaemia?
Reduced rate of synthesis of normal alpha or normal beta globin chains (thalassaemia can either be alpha or beta).
What is sickle cell disease?
Synthesis of an abnormal haemoglobin.
Why is there a low level of intracellular haemoglobin in thalassaemia?
The red cells are hypochromic (little haemoglobin) and microcytic (smaller).
What is the silent carrier state of alpha thalassaemia?
It is a deletion of a single alpha globin gene therefore it is asymptomatic, without anaemia.
What is the alpha thalassaemia trait?
This is the deletion of two alpha globin genes, it may affect both genes on one chromosome or one gene of each chromosome. There is minimal or no anaemia and no physical signs.
Microcytosis and hypochromia.
What is Haemoglobin H (HbH) disease?
This is the deletion of three alpha globin genes, leads to tetramers of B globin called HbH being formed. Moderately sever anaemia- microcytic, hypochromic anaemia with target cells and Heinz bodies in the blood film.
What are Heinz bodies?
Inclusions within red blood cells which are composed of denatured haemoglobin.
What is it called when all four alpha globin genes are deleted?
Hydrophobic getalis, excess of gamma globin chains form tetramers (Hb Bart) that are unable to deliver oxygen to the tissues, it results in death of embryo.
How does haemolytic anaemia arise?
It results from the abnormal breakdown (haemolysis) of red blood cells in blood vessels (intravascular haemolysis) or the spleen (Extravascular haemolysis).
Bone marrow can compensate for any decrease in lifespan resulting from haemolysis by increasing production so why does haemolytic anaemia occur?
Well if the average lifespan/breakdown of an erythrocyte reduces to a certain extent then increased production by the bone marrow is unable to compensate and anaemia will therefore occur.
What are the symptoms caused by haemolytic anaemia?
Shortness of breath/fatigue/ accumulation of bilirubin (Substance released when haemaglobin is broken down) leads to jaundice and gall stones (the conjugated bilirubin blocks the gall bladder ducts in the form of gall stones).
What can haemolytic anaemias be classified by?
Either inherited or acquired... Acquired (damage to cells) can be caused by... - Mechanical damage - Antibody damage - Oxidant damage - Heat damage (burns) - Enzymatic damage
Inherited (Defective gene)
- Glycolysis defect
Pyruvate kinase deficiency limits ATP production
Penthouse P pathway- g6pdh deficiency (GSH can not be regenerated)
Haemoglobin defect
What is MAHA?
Microangipathic haemolytic anaemias are a group of acquired haemolytic anaemias where red cells are damaged by physical trauma.
What does the trauma in microangiopathic haemolytic anaemia normally come from?
Red cells getting snagged as they try to pas through small vessels which are laden with fibrin stands in situations where there is an increased activation of the coagulation cascade.
Disseminated intravascular coagulation (DIC)- a condition where clotting and bleeding occur at the same time.
Thrombocytopenia purpurin- a syndrome where small thrombi form within the microvasculature.
HAEMOLYTIC uraemia Syndome (HUS)- seen more commonly in children after developing E. coli diarrhoea.
RBC also damaged by the shear stress produced by a defective heart valve ie: Aortic valve stenosis.
What are immune haemolytic anaemias Caused by?
They result from infections, lymphoproliferative disorders and reactions to drugs.
What are the two classifications of immune haemolytic anaemias?
You have: Warm or Cold haemolytic anaemias.
In warm haemolytic anaemias IgG antibodies recognise epitomes on the red cell membrane leading to macrophages in the spleen recognising the antibody coated red cells and either disposing of the whole cell by phagocytosis or nibbling a bit off. In the latter case, since some membrane is lost the red cell tends. To round up forming a Spherocyte.
What happens in cold autoimmune haemolytic anaemia?
IgM autoantibodie recognise the red cell epitomes and there is also complement fixed to the patient red cells. The IgM autoantibodies bind best at cooler temps, they tend to bind to the red cells in more distal parts of the body ie: fingertips.