Anaemia Flashcards
What is anaemia?
“without blood”
Reduced red blood cells
State the parameters for defining anaemia in an adult male (Hb and haematocrit levels)
Hb less than 130g/L
Hct 0.38-0.52
State the parameters for defining anaemia in an adult female (Hb and haematocrit levels)
Hb less than 120g/L
Hct 0.37-0.47
What is haematocrit?
Ratio/percentage of whole blood that is made up of red cells if the sample was left to settle
What cells represent circulatory red cells that have just left the bone marrow?
Reticulocytes
How does the blood film of reticulocytes appear?
Polychromatic
How is anaemia classified by pathophysiology?
Decreased production of red cells (reduced or ineffective erythropoiesis) [low reticulocyte count]
Increased destruction of red cells (haemolysis, bleeding) [high reticulocyte count)
What morphological characteristic can be used to classify anaemia?
Mean cell volume
How can mean cell volume be used to distinguish between cytoplasmic and nuclear defects in erythropoiesis?
Low MCV suggests problems with haemoglobinisation in the cytoplasm
High MCV suggests problems with red cell maturation
Deficiency in haemoglobin production results in what type of anaemia?
Microcytic anaemia - cells are small (low MCV) and hypochromic (lack colour)
List some causes of microcytic anaemia
Haem deficiency (lack of iron, problem with porphyrin synthesis) Globin deficiency (thalassaemia)
Circulating iron is bound to what?
Transferrin
Iron is stored as ferritin where in the body?
Liver
How can iron deficiency be confirmed?
Anaemia (less functional iron) Low ferritin (less stored iron)
List some causes of iron deficiency
Dietary insufficiency
Blood loss
Malabsorption
Pregnancy
High mean cell volume is associated with which type of anaemia?
Macrocytic anaemia - cells are big
What is the difference between macrocytosis and macrocytic anaemia?
Macrocytosis: raised MCV, normal RBC count
Macrocytic anaemia: raised MCV, low RBC count
How many binding sites are there on a transferrin molecule?
2
What unit is MCV measured in?
Femtolitres (fl)
1 femtolitre = 10^-15 litres
What is the range for a normal MCV?
80-100 fl
What is a megaloblast?
Abnormally large red cell precursor with an immature nucleus
Macrocytic anaemia can be caused by megaloblastic cells. What is the characteristic microscopic appearance of these red cells?
Immature nucleus
Normal cytoplasm
Big cell
What is the consequence of a megaloblastic cell?
Cytoplasm and haem synthesis is fully developed even though nucleus is immature; cell senses it has enough Hb and doesn’t divide anymore, leading to macrocytosis
List some causes of megaloblastic anaemia
B12 deficiency
Folate deficiency
Drugs
Inherited conditions
Why does lack of B12 and folate cause megaloblastic anaemia?
B12 and folate are essential cofactors for nuclear maturation - enable reactions for DNA synthesis
Thus deficiency leads to DNA defects
Which 2 biochemical cycles involving folate and B12 are involved in DNA synthesis?
Methionine cycle
Folate cycle
Where in the body does B12 bind to intrinsic factor?
Ileum
List some causes of B12 deficiency
Dietary insufficiency (vegetarians) Small bowel resection Atrophic gastritis Gastrectomy Pancreatitis Malabsorption (Coeliac, IBD)
Where in the body is dietary folate absorbed?
Duodenum and jejunum
How long does the body store B12 and folate respectively?
B12: 2-4 years
Folate: 4 months
State the daily requirements of B12 and folate
B12: 1-3 micrograms/day
Folate: 100 micrograms/day
List some causes of folate deficiency
Dietary insufficiency
Malabsorption
Excess utilisation (haemolysis, pregnancy, malignancy)
Drugs (anticonvulsants)
List clinical features of B12 and folate deficiency
Signs of anaemia Weight loss Diarrhoea Infertility Sore tongue Jaundice Developmental problems
B12 deficiency can cause issues with the myelin sheath. What neurological problems may result?
Dorsal column abnormality Lateral tract degeneration Neuropathy Dementia Psychiatric manifestations
What is pernicious anaemia?
Autoimmune condition where gastric parietal cells are destroyed, causing decreased intrinsic factor and thus B12 deficiency
How is macrocytic anaemia diagnosed in the lab?
Blood film: macrovalocytes and hypersegmented neutrophils (more than 5 segments)
B12 and folate serum assay
Antibodies: parietal-cell, intrinsic factor
List treatment for megaloblastic anaemia
Treat cause
B12 injections
Folic acid tablets
Red cell transfusion if life-threatening
List some causes of non-megaloblastic anaemia
Alcoholism
Liver disease
Hypothyroidism
Marrow failure
What is spurious macrocytosis?
The size of the red cell is normal but the MCV is high
What causes a spurious macrocytosis?
Acute blood loss/red cell breakdown response: increase in reticulocytes, which are bigger than red cells, which are analysed as part of MCV
Reticulocytosis is a marker of what?
Red cell production
What compound is a product of red cell breakdown that causes pale urine?
Urobilinogen
What is the commonest cause of hypochromic microcytic anaemia?
Iron deficiency
