Anaemia and Polycythaemia Flashcards
Define anaemia.
Anaemia = reduction in amount of Hb in given blood volume below what would be expected in comparison with healthy subject of same age and gender.
RBC, Hct also reduced.
In what two ways can anaemia occur?
Reduction in amount of Hb in blood stream.
Increase in volume of blood plasma.
Why is reduction in absolute Hb considered the practical definition of anaemia?
Increased plasma volume in healthy people will be corrected as excess circulation fluid is excreted, so anaemia can be regarded as a decrease in absolute haemoglobin.
Name some mechanisms through which anaemia can occur?
Reduced RBC production in bone marrow
Loss of blood from body
Reduced survival of circulating RBC
pooling of RBC in large spleen
How is anaemia classified based on cell size?
microcytic (normally hypochromic)
normocytic (normally normochromic)
macrocytic (normally normochromic)
Name some common causes of microcytic anaemia.
Defect in haem synthesis.
- iron deficiency
- anaemia of chronic disease.
Defect in globin synthesis (thalassaemia)
- defect in alpha chain syn (alpha thalassaemia)
- defect in beta chain syn (beta thalassaemia)
How might macrocytic anaemia occur?
Macrocytic anaemia is usually due to abnormal haemopoiesis. RBC precursors continue to grow and synthesise haemoglobin but fail to divide normally.
: . RBC are larger than normal.
What is a megaloblast?
An abnormal bone marrow erythroblast. Larger than normal with nucleo-cytoplasmic disassocation.
Name some causes of macrocytic anaemia.
Megaloblastic erythropoiesis (nucleus maturation delay while cytoplasm grows) - e.g. due to Vit B12/folic acid deficiency.
Pre-mature release of cells from bone marrow (young RBC 20% larger).
Liver disease/ethanol toxicity.
Use of drugs interfering with DNA synthesis.
Significant blood lost (with sufficient iron stores)
Haemolytic anaemia.
How can haemolytic anaemia be classified?
Intrinsic/extrinsic causes of RBC abnormality.
Whether it is inherited or acquired.
Whether it is intravascular or extravascular.
Diagram comparing inherited and acquired haemolytic anaemia
Name the mechanisms of normocytic anaemia.
Recent blood loss
Failure of RBC production
Pooling of RBC in spleen
Name some causes of normocytic anaemia.
Peptic ulcer
Oesophageal varices
Trauma
Failure of RBC production
- iron deficiency, early stages.
- renal failure
- bone marrow failure/suppression
- bone marrow infiltration.
Hypersplenism
When should you suspect haemolytic anaemia?
Otherwise inexplicable.
Evidence of abnormal RBC
Evidence of increased RBC breakdown
Evidence of increased bone marrow activity.
In hereditary spherocytosis haemolytic anaemia what is the site of defect?
membrane
What is the site of defect associated with sickle cell anaemia (haemolytic anaemia)
Hb
What defective pathway is associated with pyruvate kinase deficiency (haemolytic anaemia)?
glycolytic pathway
What defect is associated with glucose-6-phosphate dehydrogenase deficiency (haemolytic anaemia)?
Pentose shunt.
Table to show site of defects and examples in acquired haemolytic anaemia
What is hereditary spherocytosis?
haemoltyic anaemia or chronic compensated haemolysis resulting from inherited intrinsic defect of RBC membrane
Cell loses membrane in splene –> spherocytic.
Explain the consequences of hereditary spherocytosis.
RBC less flexible - removed prematurely by psleen (extravascular haemolysis).
Bone marrow increased RBC output –> polychromasia and reticulocytosis.
Haemolysis –> jaundice + gallstones.
Name an osmotic characteristic of spherocytes.
Prone to haemolyse when osmotic pressure is reduced.
How can hereditary spherocytosis be treated?
Splenectomy.
Good diet.
Folic acid tablets.
What is the role of G6PD?
important enzyme in pentose phosphate shunt.
Essential for protection of RBC from oxidant damage.
