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MCD Haematology > Anaemia > Flashcards

Anaemia Flashcards

1
Q

What is anaemia?

A

Reduction in amount of haemoglobin in a given volume of blood below what would be expected in comparison with a healthy subject of same age and gender

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2
Q

What else is also normally reduced during anaemia?

A

RBC and Hct

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3
Q

Why can anaemia in a healthy person not be due to increase in plasma volume?

A

Excess fluid in circulation will be excreted

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4
Q

What are the mechanisms of anaemia?

A

Reduced production of red blood cells/haemoglobin in the bone marrow
Loss of blood from the body (haemorrhage)
Reduced survival of red blood cells in circulation (haemolytic)
Pooling of red blood cells in a very large spleen

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5
Q

How is anaemia classified?

A

Cell size:
Microcytic- usually hypochromic
Normocytic- normochromic
Macrocytic- normochromic

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6
Q

What are the common causes of microcytic anaemia?

A

Defect in haem synthesis:
Iron deficiency
Anaemia of chronic disease
Defect in global synthesis (thalassaemia):
Defect in alpha chain synthesis (alpha thalassaemia)
Defect in beta chain synthesis (beta thalassaemia)

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7
Q

What does macrocytic anaemia usually result from?

A

Abnormal haemopoiesis so red cell precursors continue to synthesise haemoglobin and other cellular proteins but they fail to divide normally so much larger

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8
Q

What is megaloblastic erythropoiesis?

A

A delay in the maturation of the nucleus while the cytoplasm continues to mature and cell continues to grow

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9
Q

What is a megaloblast?

A

An abnormal bone marrow erythroblast

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10
Q

What are key features of megaloblasts?

A

Larger than normal and shows nucleo-cytoplasmic dissociation

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11
Q

What can megaloblastic erythropoiesis lead to?

A

Macrocytosis

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12
Q

What is an alternative mechanism for macrocytosis?

A

Premature release of cells from the bone marrow

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13
Q

How do reticulocytes compare in size to normal erythrocytes?

A

They are 20% bigger

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14
Q

What are common causes of macrocytic anaemia?

A

Megaloblastic anaemia as a result of lack of vitamin B12 or folic acid
Use of drugs interfering with DNA synthesis e.g. chemotherapy or azathioprine
Liver disease and ethanol toxicity
Recent major blood loss with adequate iron stores
Haemolytic anaemia

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15
Q

What are the mechanisms for normocytic normochromic anaemia?

A

MCV and MCH are normal so:
Recent blood loss
Failure to produce red blood cells
Pooling of red blood cells in the spleen

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16
Q

What causes normocytic normochromic anaemia?

A 
Peptic ulcer
Oesophageal varices
Trauma
Failure of production of red blood cells
Early stages of iron deficiency or anaemia of chronic disease
Renal failure
Bone marrow failure or suppression
Bone marrow infiltration 
Hypersplenism
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17
Q

What is haemolytic anaemia?

A

Anaemia resulting from shortened survival of red blood cells in the circulation

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18
Q

What can cause haemolysis?

A

Intrinsic abnormality of red cells or extrinsic factor acting on normal red cells

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19
Q

What is normal red cell survival?

A

120 days

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20
Q

What is the difference between intravascular and extravascular haemolysis?

A

Intravascular occurs if there is very acute damage to the red cell
Extravascular occurs when defective red cells are removed by the spleen

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21
Q

What other way can haemolytic anaemia be classified?

A

Inherited or acquired

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22
Q

What examples of inherited haemolytic anaemia are there?

A

Abnormalities of cell membrane, haemoglobin or enzymes in RBC

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23
Q

What examples of acquired haemolytic anaemia are there?

A

They usually result from extrinsic factors such as microorganisms, chemicals or drugs that damage the red cell

24
Q

What will cause a red cell to burst?

A

Abnormal cell membrane
Abnormal haemoglobin
Defect in glycolytic pathway

25
Q

What does G6PD stand for?

A

Glucose-6 phosphate dehydrogenase

26
Q

What is G6PD?

A

Enzyme involved in pentose phosphate pathway

27
Q

What is the pentose phosphate pathway?

A

Metabolic pathway parallel to glycolysis that generates NADPH and pentoses

28
Q

What is the pentose phosphate pathway the only source of in red blood cells?

A

Reduced glutathione

29
Q

What does G6PD protect you from?

A

Substantial risk of damage from oxidising free radicals due to the oxygen carrying role of red blood cells

30
Q

What are people with G6PD deficiency at risk of?

A

Haemolytic anaemia in states of oxidative stress

31
Q

What is pyruvate kinase involved with?

A

Last reaction of glycolysis

32
Q

What will a deficiency in pyruvate kinase result in?

A

Red blood cells with decreased energy- Red blood cells can’t synthesise ATP so cellular death occurs

33
Q

What would make you suspect haemolytic anaemia?

A

Unexplained anaemia that is normochromic and either normocytic or macrocytic
Evidence of morphologically abnormal red cells
Evidence of increased red cell breakdown
Evidence of increased bone marrow activity

34
Q

What is microangiopathic haemolytic anaemia?

A

Red cells are being broken down within the circulation rather than the whole red cell being taken up and broken down in the spleen, they are being smashed up within the circulation

35
Q

How can haemolytic anaemia lead to jaundice?

A

Increase in red blood cell breakdown leads to an increase in bilirubin leading to jaundice

36
Q

What is hereditary spherocytosis?

A

Haemolytic anaemia or chronic compensated haemolysis resulting from an inherited intrinsic defect of the red cell membrane

37
Q

How do spherocytes compare to normal erythrocytes?

A

Larger and rounder
Increased MCHC
Less flexible

38
Q

What happens to spherocytes?

A

They are less flexible (can’t go through sinusoids) so removed prematurely in spleen- extravascular haemolysis

39
Q

How does bone marrow respond to haemolysis?

A

Increased output of red cells leading to polychromasia and reticulocytosis

40
Q

What is polychromasia?

A

The presence of certain blue red blood cells seen in blood films stained with Romanowsky stains as well as normal pink cells. Cells that appear blue are juvenile red blood cells

41
Q

What is the only effective treatment for hereditary spherocytosis?

A

Splenectomy- only done in extreme situations

42
Q

What is important for the diet of someone with hereditary spherocytosis?

A

To avoid vitamin deficiency due to the increased usage to make more red blood cells, vitamin B12, folic acid and iron

43
Q

What examples of extrinsic oxidants are there?

A

Foodstuffs- broadbeans
Chemicals- naphthalene
Drugs- dapsone

44
Q

Where is the gene for G6PD deficiency?

A

X chromosome

45
Q

What sort of individuals are most commonly affected by G6PD deficiency?

A

Homozygous males

46
Q

What does G6PD deficiency usually cause?

A

Intermittent, severe intravascular haemolysis as result of infection or exposure to an exogenous oxidant

47
Q

What does acute haemolytic anaemia result from?

A

Production of antibodies against red cell antigens- immunoglobulin bound to red cell membrane is recognised by splenic macrophages which remove part of the cell membrane leading to spherocytosis

48
Q

How do you diagnose spherocytosis?

A

Finding spherocytes and increased reticulocyte count
Detecting immunoglobulin on red cell surface
Detecting antibodies to red cell antigens or other antibodies in plasma

49
Q

How do you treat spherocytosis?

A

Use of corticosteroids and other immunosuppressive agents

Splenectomy for severe cases

50
Q

What is polycythaemia?

A

Too many red blood cells in the circulation

51
Q

What is Hb, RBC and Hct like in polycythaemia?

A

All raised

52
Q

What is pseudopolycythaemia?

A

High Hb, RBC and Hct from a decrease in plasma volume

53
Q

What can cause polycythaemia?

A

Doping
Too much erythropoietin- potentially due to altitude
Tumour- renal or other tumour secreting too much EPO
Abnormal function of bone marrow-
Increased erythropoiesis
Intrinsic bone marrow disorder- polycythaemia vera

54
Q

What can polycythaemia result in?

A

Vascular obstruction due to hyper viscosity of the blood

55
Q

If there is no physiological reason for high haemoglobin or there is extreme hyperviscosity, what can be done?

A

Venesection- blood can be removed to thin the blood

56
Q

How would you treat polycythaemia due to intrinsic bone marrow disease?

A

Drugs can be used to reduce the production of red blood cells by the bone marrow

MCD Haematology (11 decks)

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