Haemolytic anaemia Flashcards
What is the definition of haemolytic anaemia?
- Anaemia related to reduced red blood cell lifespan
* No blood loss and no haematinic deficiency (folate/B12/iron)
Describe the haematology if red cell lifespan is 20-100 days
Compensated haemolytic state
•Hb normal
•Reticulocytes increased
•(unconjugated) bilirubin increased
Describe the haematology if red cell lifespan is less than 20 days
Haemolytic anaemia •Hb decreased •Reticulocytes increased •Bilirubin incereased •Splenomegaly (often palpable)
Why may someone in a chronic haemolytic state have gall stones?
Due to the increased bilirubin, causing pigment gall stones
What is hyposplenic state?
Rises from encapsulated organism pneumococcus, meningococcus, haemophilus
What broad categories that cause the congenital haemolytic anaemias?
- Abnormalities of the RBC membrane
- Abnormalities of the RBC enzymes
- Haemoglobinopathies
Hereditary spherocytosis
- Congenital haemolytic anaemia due to abnormalities of the red blood cell membrane
- Autosomal dominant
- RBCs spherocytic and polychromatic
- Jaundice
- Splenomegaly
Explain pyruvate kinase deficiency anaemia
- required for the conversion of ADP to ATP so ATP becomes depleted and red cells haemolyse
- results in chronic extravascular haemolytic anaemia
Explain glucose 6 phosphate dehydrogenase deficiency
- required for turning NADP to NADPH
- acute episodic intravascular haemolysis (but for most of the time normal) from oxidative stress
- X linked recessive
In a glucose 6 phosphate dehydrogenase deficiency, what can cause episodes of acute haemolysis?
Oxidative stress: •Favism •Drugs - antimalarials - sulphonamides - others
What are the types of acquired haemolytic anaemias?
- Autoimmune: warm type or cold type
- Isoimmune e.g. haemolytic disease of newborn
- Non immune e.g. fragmentation haemolysis
Explain when intravascular haemolysis may take place
- when there has been mechanical trauma to the red cell e.g. defective mechanical heart valves
- Following ABO incompatible blood transfusion resulting in the production of anti-A and/or anti-B IgM antibodies
- Malaria
- Cold IgM autoantibodies
What are the causes of cold autoimmune haemolytic anaemia?
•Primary: idiopathic •secondary; - infection-mycoplasma pneumoniae - infectious mononucleosis - lymphoproliferative disorders
What are the main laboratory findings in intravascular haemolysis?
- anaemia, reticulocytosis and raised unconjugated bilirubin
- haemoglobinaemia and haemoglobinuria
- haemosiderinuria
Explain why haemosiderin may appear in the urine due to intravascular haemolysis
- there is an increased amount of haemoglobin
- haemoglobin saturates the binding protein in the plasma, haptoglobin
- Excess haemoglobin is filtered at the glomerulus resulting in haemoglobinuria
- The renal tubules reabsorb some haemoglobin from the urine which is broken down to form haemosiderin which can then also appear in the urine
Explain what happens in extravascular haemolysis
- It occurs in the reticuloendothelial system, particularly in the spleen
- It is often related to the production of warm IgG autoantibodies
Describe what happens in extravascular haemolysis caused by the production of warm antibodies
- IgG attaches to the red cell antigen and damages the membrane
- The RBCs become spherocytic and are phagocytosed by the RES, particularly the spleen
- As a result the spleen becomes enlarged
What are the causes of warm type autoimmune haemolytic anaemia?
•primary: idiopathic - 55-60% • secondary: - lymphoproliferative disorders e.g. chronic lymphocytic leukaemia - neoplasms - SLE - connective tissue disorders - drugs
State the different autoimmune haemolytic anaemias
- Drug induced - the drug acts as a hapten
- immune complex
- autoimmune
Explain the direct Coombs test
- Add anti human immunoglobulin
* If there are antibodies (with or without complement) the red cells will agglutinate
Explain the indirect Coombs test
- Used to detect antibodies floating freely in the blood to check prior to transfusion
- Plasma from the patient is mixed with a sample of blood
- Anti-human immunoglobulin is added, if agglutination occurs it is positive
What is the treatment of cold autoimmune haemolytic anaemia?
- If due to a mycoplasma infection it is self limiting
* if idiopathic keep the patient warm (IgM antibodies won’t fix to the red blood cells)
How do you treat warm autoimmune haemolytic anaemia?
- Stop any drugs
- Use steroids if idiopathic
- Immunosuppression
- Splenectomy
Describe haemolytic disease of the newborn
- Rhesus negative mother with a rhesus positive baby
- some red cells from the baby leak into the mothers circulation
- RhD+ cells raised IgG antibodies which can cross the placenta, attacking the baby’s red cells and cause haemolytic anaemia
