Haemolytic anaemias Flashcards
Define haemolytic anaemia.
Increased destruction of erythrocytes.
Describe the classification of haemolytic anaemias
Intravascular - erythrocytes destroyed in circulation.
Extravascular - erythrocytes destroyed by macrophages of reticuloendothelial system.
Hereditary - defects in erythrocyte membrane, metabolism or Hb.
Acquired - erythrocytes targeted by antibodies produced by immune system.
Describe the aetiology of hereditary spherocytosis.
Spherocytes are very spherical erythrocytes, produced in hereditary spherocytosis.
Deficiencies in membrane proteins, such as spectrin, cause impaired interactions between proteins and phospholipid bilayer, resulting in the erythrocyte membrane peeling away. Spherocytes can get trapped or burst as they don’t have the strength or flexibility needed to withstand stresses of circulation.
Describe extravascular haemolysis.
Macrophages within spleen recognise and destroy abnormal erythrocytes.
Splenomegaly can occur as erythrocytes get stuck in sinusoids of spleen as they are rigid, which has a negative effect on spleen.
Describe some symptoms of hereditary spherocytosis.
Anaemia : breathless, fatigue, pale mucous membranes.
Jaundice: increased levels of bilirubin, due to breakdown of Hb.
Splenomegaly: enlargement of spleen due to spherocytes getting stuck in spleen sinusoids, and macrophages destroying a lot of spherocytes.
Pigment gallstones: due to increased erythrocyte destruction.
What type of samples are collected for hereditary spherocytosis?
K-EDTA tubes to collect whole blood.
Serum separator tubes to collect serum. Can be used to detect antibodies or markers of anaemia.
Urine to look for products of erythrocyte breakdown.
Samples must be transported immediately or under four hours, and be refrigerated at 4°C, to retain sample integrity.
Describe some tests to diagnose hereditary spheroytosis.
Full blood count
Blood film
Direct antiglobulin test
Biochemistry
EMA binding test
What would be been in a FBC in hereditary spherecytosis?
Decreased Hb and MCV.
Increased MCHC, RDW and reticulocytes.
What would be seen in a blood film for hereditary spherocytosis?
Spherocytes - smaller, circular and lack centre of pallor.
Describe direct antiglobulin test (DAT) and what the results would be in hereditary spherocytosis.
DAT detects if patients’ erythrocytes are coated with antibodies.
In a positive result, when patients’ erythrocytes are incubated with Coombs reagent, the erythrocytes agglutinate, as Coombs reagent binds with antibodies on patients erythrocytes.
As hereditary spherocytosis isn’t an antibody driven condition, DAT will be negative.
Describe the results for EMA binding test in HS.
The EMA binding test uses flow cytometry.
A fluorescent probe binds to band 3 protein on healthy erythrocytes.
In HS, abundance of band 3 is decreased due to decreased surface area.
In HS, mean channel fluorescence is decreased.
Give some examples of treatment for HS.
Folate therapy to promote normal erythropoiesis as compensation for breakdown of erythrocytes.
Splenectomy to decrease haemolysis.
However, increases risk of infections so patients must be on lifelong antibiotics.
Describe the aetiology of autoimmune haemolytic anaemia.
Autoimmune haemolytic anaemia is caused by autoantibody production.
50% of cases are idiopathic, while the other 50% is a secondary cause of infections, cancers, chronic lymphocytic leukaemia or Shrogan syndrome.
Describe warm AIHA
80-90% of AIHA.
Caused by warm-reactive IgG antibodies, which bind optimally at 37 C.
IgG can bind with or without complement.
Extravascular haemolysis.
Describe the classification of autoimmune haemolytic anaemia.
Warm AIHA
Mixed AIHA
Cold AIHA
