Anaemia and polycythaemia

Question 1

What is anaemia?

Answer 1

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

Question 2

What does a FBC look like in anaemia?

Answer 2

Reduced Hb, RBC, Hct

Question 3

What are the vague mechanisms of anaemia?

Answer 3

1. Reduced production of red cells/haemoglobin in BM
2. Haemorrhage (blood loss)
3. Reduced survival of red cells in circulation (haemolytic)
4. Pooling of red cells in v large spleen

Question 4

Explain the difference between mechanism and cause of anaemia

Answer 4

Mechanism e.g. reduced synthesis of haemoglobin in BM

Cause e.g. condition causing reduced synthesis of haem or condition causing reduced synthesis of globin

Could be several causes to a single mechanism

Question 5

Why is classification of anaemia important?

Answer 5

Classification on basis of cell size can help suggest specific causes –> correct treatment

Question 6

How is anaemia classified on basis of cell size?

Answer 6

Microcytic - smaller than normal red cells
Normocytic - normal size red cells
Macrocytic - larger than normal red cells

Question 7

How do the classifications of anaemia differ in their central pallor?

Answer 7

Microcytic - hypochromic

Normocytic and macrocytic - normochromic

Question 8

What are the common causes of microcytic anaemia?

Answer 8

Defect in haem synthesis:

• Iron deficiency
• Anaemia of chronic disease

Defect in globin synthesis (thalassaemia):

• Defect in alpha chain synthesis
• Defect in beta chain synthesis

Question 9

What are the possible mechanisms behind macrocytic anaemia?

Answer 9

1. Abnormal haemopoiesis - red cell precursors continue to synthesise haemoglobin and other cellular proteins but fail to divide normally tf red cells are much larger than normal
2. Premature release of cells from BM (megaloblastic)

Question 10

What are the common causes of macrocytic anaemia?

Answer 10

1. Megaloblastic anaemia due to lack of vit B12 or folic acid
2. Recent major blood loss w/adequate iron stores - BM releases reticulocytes to compensate
3. Haemolytic anaemia (reticulocytes increase due to loss of red cells)
4. Liver disease
5. Ethanol toxicity
6. Use of drugs interfering w/DNA synthesis, e.g. chemo, azathioprine

Question 11

What are the mechanisms behind normocytic anaemia?

Answer 11

1. Recent blood loss
2. Failure of production of red cells
3. Pooling of red cells in spleen

Question 12

What are the common causes of normocytic anaemia?

Answer 12

Mech: recent blood loss:

• Peptic ulcer
• Oesophageal varices
• Trauma - RTC

Mech: failure of production of red cells:

• Early stages of iron deficiency or anaemia of chronic disease
• Renal failure
• BM failure or suppression
• BM infiltration - cancer spread to BM

Mech: pooling of red cells in spleen:
- Hypersplenism, e.g. portal cirrhosis

Question 13

What are the major causes of haemolysis?

Answer 13

Acute damage to red cell –> intravascular haemolysis

Defective red cells removed by spleen –> extravascular haemolysis

Often haemolysis is partly both

Question 14

What are the important causes of haemolytic anaemia?

Answer 14

Inherited:
Hereditary spherocytosis
Sickle cell anaemia
Pyruvate kinase deficiency
Glucose-6-phosphate DH deficiency

Acquired:
Autoimmune haemolytic anaemia
Microangiopathic haemolytic anaemia
Malaria

Question 15

What is haemolytic anaemia?

Answer 15

Anaemia resulting from shortened survival of red cells in the circulation

Question 16

How is a haemolytic anaemia recognised?

Answer 16

• Otherwise unexplained anaemia that is normochromic and normocytic or macrocytic
• Evidence of morphologically abnormal red cells (e.g. elliptocytes, irregularly contracted cells)
• Evidence of increased red cell breakdown (fragments) - microangiopathic haemolytic anaemia
• Evidence of increased BM activity

Question 17

What are the mechanisms behind polycythaemia?

Answer 17

Decrease in plasma volume - pseudopolycythaemia or apparent polycythaemia

Increase in number of circulating red cells - true polycythaemia

Question 18

What are the causes of polycythaemia?

Answer 18

1. Blood doping
2. Inappropriately elevated erythropoietin
3. Inappropriately administered erythropoietin
4. Tumour - kidney, liver, fibroids –> inappropriate levels of EPO secreted
5. Abnormal BM function: polycythaemia vera (inappropriately increased erythropoiesis independent of EPO)

Question 19

What is polycythaemia?

Answer 19

Too many red cells in circulation

Increased Hb, RBC, Hct compared with normal subjects of same age and gender

Question 20

What is polycythaemia vera?

Answer 20

Intrinsic BM disorder
Inappropriately increased erythropoiesis that is independent, or largely independent, of EPO
Chronic myeloproliferative neoplasm

Question 21

Explain autoimmune haemolytic anaemia

Answer 21

Acute
Results from production of antibodies against red cell antigens
Ig bound to red cell membrane is recognised by splenic macrophages
Macrophages remove parts of cell membrane
Causes spherocytosis
Increased rigidity

Red cells removed from circulation by spleen

Question 22

How are anaemias classified on the basis of mechanism?

Answer 22

1. Hypoproliferative - proliferation defect
2. Ineffective -maturation defect
3. Haemolytic - survival defect