Session 5- haemolytic anaemias Flashcards
How does thrombotic thrombocytopenic purpura cause haemolytic anaemia?
Small thrombi in the microvasculature cause RBC’s to lyse/ damage as they squeeze through
(microangiopathic haemolytic anaemia, MAHA)
What are schistocytes?
Fragments of RBC in a blood smear due to RBC lysis
What are warm and cold autoantibodies?
Warm autoantibodies (IgG) label RBC’s in warmer conditions. They are recognised and removed by the RES
Cold autoantibodies (IgM) bind RBC’s in the distal areas of the body. They span several cells so can cause RBC agglutination which can block vessels
How does complement cause damage to the RBC’s in autoimmune anaemia?
Binds with cold antibody (IgM)
- creates holes in the membrane
- acts as an opsonin for the RES
Which test can diagnose autoimmune haemolytic anaemia?
direct Coombs test
- add a labelled antibody complementary to the autoantibody. The RBC’s will clump
Pyruvate kinase deficiency is cause dby mutation in which gene?
PKLR gene
Why do the RBC’s lyse in hereditary spherocytosis?
- A mutation in ankyrin/ protein 4.2/ etc dissociates the cytoskeleton and plasma membrane
- Cell becomes spherical, reducing its surface area and so deformability
- Cells are trapped/ damaged passing through spleen (extravascular haemolysis)
- Removed by spleen
How do you treat hereditary spherocytosis?
What is the inheritance pattern?
Splenectomy
(Problem of extravascular haemolysis not intravascular)
Autosomal dominant
Why might Howell Jolly bodies be seen in hereditary spherocytosis?
(DNA in RBC’s)
The spleen would usually remove these abnormal cells but is working extra hard in haemolytic anaemia
Which chains make up foetal haemoglobin?
x2 alpha, x2 gamma
How do RBC’s become sickle shaped in SC anaemia?
Polymerise in low oxygen conditions
Repeated sickling damages the membrane so that it loses elasticity and does not return to normal shape
How do you treat SC anaemia?
Haematopoietic stem cell transplantation (rare)
What is thalassemia major?
A serious thalassemia (reduced expression of globin chains in haemoglobin) where the patient needs blood transfusions for life
How can the level of haemoglobin be normal in heterozygous beta thalassaemia?
Bone marrow increases synthesis of RBC’s to compensate for the low rate of globin chain synthesis in each cell (microcytosis)
Which alpha thalassaemia causes death in utero?
if all 4 alpha globin genes are mutated
