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Year 2 Collin > Haem 3 - Anaemia and Polycythaemia > Flashcards

Haem 3 - Anaemia and Polycythaemia Flashcards

1
Q

What is anaemia

A

Reduction in amount of Hb in given volume of blood (below what would be normal for same age and gender healthy subject)

Hb reduced, usually RBC & PCV/Hct reduced too

It can be from increase in plasma volume though usually due to reduction in absolute amount of Hb

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2
Q

What are the mechanisms of anaemia

A
  1. Reduced production of RBC/Hb in bone marrow
  2. Loss of blood from body
  3. Reduced survival of RBCs in circulation
  4. Pooling of RBC in very large spleen
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3
Q

How can anaemia be classified based on cell size

A
  1. Microcytic (usually also hypo chromic)
  2. Normocytic (usually normochromic)
  3. Macrocytic (normochromic)
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4
Q

What are the causes of microcytic anaemia

A
  1. Defect in haem synthesis due to iron deficiency or anaemia of chronic disease (e.g. Rheumatoid arthritis)
  2. Defect in global synthesis (thalassaemia) caused by defect in a-chain synthesis or b-chain synthesis
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5
Q

How is macrocytic anaemia usually caused

A

Macrocytic anaemia usually due to abnormal haemopoiesis —> RBC precursors continue to synthesise Hb and other cellular proteins —> fail to divide normally

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6
Q

Megaloblastic erythropoiesis can cause macrocytic anaemia. How?

A

Delay in maturation of nucleus - whilst cytoplasm continues to grow.

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7
Q

What is a megaloblast

A

Abnormal bone marrow erythroblast –> larger than normal and shows nuclei-cytoplasmic dissociation

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8
Q

What is an alternative mechanism of macrocytosis

A

Premature release of cells from bone marrow (increased reticulocyte)

Reticulocyte = 20% larger than mature RBC

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9
Q

Megaloblastic anaemia - causes

A
  1. Lack of Vit B12 / folic acid
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10
Q

What are the common causes of macrocytic anaemia

A
  1. Megaloblastic anaemia - lack of Vit B12 / folic acid
  2. Drugs interfering with DNA synthesis
  3. Liver disease and ethanol toxicity
  4. Major blood loss (with adequate iron stores)
  5. Haemolytic anaemia
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11
Q

What are the mechanisms of normocytic normochromic anaemia

A
  1. Recent blood loss
  2. Failure of production of RBC
  3. Pooling of RBC in spleen
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12
Q

What are the causes of normocytic normochromic anaemia

A
  1. Peptic ulcer, oesophageal varices, trauma
  2. Failure of production of RBC (e.g. due to renal failure / bone marrow failure or suppression)
  3. Hypersplenism e.g. portal cirrhosis
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13
Q

What is haemolytic anaemia

A

Anaemia resulting from shortened survival of RBC in circulation

Can result from intrinsic abnormality of RBC, or extrinsic factors acting on normal RBC

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14
Q

Haemolytic anaemia can be classified as inherited or acquired - describe each

A

Inherited haemolytic anaemia = abnormalities in cell membrane/Hb/enzymes in red cell

Acquired haemolytic anaemia = extrinsic factors (Eg microorganisms, chemicals, drugs) that damage red cell

(extrinsic factors can also interact with RBCs that have intrinsic abnormality)

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15
Q

Haemolytic anaemia can be classified as intravascular or extravascular. Describe each

A

Intravascular haemolysis = very acute damage to the red cell

Extravascular haemolysis = when defective red cells are removed by spleen

Often mixture of intravascular and extravascular

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16
Q

Sickle cell lifespan = 20 days. Normal RBC lifespan =?

A

120

17
Q

What are inherited forms/causes of haemolytic anaemia

A
  1. Abnormal RBC membrane - hereditary spherocytosis
  2. Abnormal Hb - Sickle cell anaemia
  3. Defect in glycolytic pathway (e.g. pyruvate kinase deficiency)
  4. Defect in enzymes of pentose shunt (e.g. G6PD deficiency)
18
Q

What are acquired forms/causes of haemolytic anaemia

A
  1. Damage to RBC membrane (AIHA / snake bite)
  2. Damage to whole RBC (MAHA)
  3. Oxidant exposure/damage to RBC membrane and Hb (e.g. dapsone or primaquine)

NB- Primaquine/dapsone combined with defective Pentose shunt enzymes (G6PD deficiency - inherited) is a precipitation of episodic acute haemolytic - this is a combination of extrinsic and inherited conditions in tandem

19
Q

When should we suspect haemolytic anaemia

A

Normochromic anaemia, either normocytic or microcytic - no other explanations

Evidence of morphologically abnormal RBC
Evidence of increased RBC breakdown
Evidence of increased bone marrow (also lactate dehydrogenase increased)

20
Q

Describe hereditary spherocytosis

A

Haemolytic anaemia or chronic compensated haemolysis - resulting from inherited intrinsic defect of RBC membrane

After entering circulation, cells lose membrane in the spleen - become spherocytic

Spherocytic RBC = less flexible and removed prematurely by spleen (extravascular haemolysis)

21
Q

What happens if extravascular haemolysis occurs as a result of hereditary spherocytosis

A

Bone marrow increases RBC output - leading to polychromasia + reticulocytosis

Haemolysis leads to increased bilirubin production, jaundice and gallstones

22
Q

How is hereditary spherocytosis treated

A

Only effective treatment = splenectomy (but has own risks so only done in emergency)

Good diet important to prevent secondary folic acid deficiency - may also take a folic acid tablet daily

23
Q

What is G6PD

G6PD deficiency = intravascular haemolysis

A

Glucose-6-Phosphate Dehydrogenase

Important enzyme in pentose phosphate shunt - essential to protect RBC from oxidant damage

(Oxidants may be generated in bloodstream (e.g. during infection) or may be exogenous)

24
Q

What extrinsic oxidants may exacerbate a G6PD deficiency

A

Foodstuffs (broad beans), chemicals, drugs

G6PD gene is on X Chr - usually hemizygous males affected (but sometimes homozygous females)

25
Q

How does G6PD deficiency show

A

Associated with appearance of irregularly contracted cells

Hb denatured and forms round inclusions - Heinz bodies

26
Q

What is one way to treat acute haemolysis

A

Blood transfusion

27
Q

Describe autoimmune haemolytic anaemia

A

Production of auto-antibodies - directed at RBC antigens

Ig bound to RBC is recognised by splenic macrophages - this results in spherocytosis as part of the RBC cell membrane are removed

(Complement that is bound to Ig can also be recognised)

28
Q

How is autoimmune haemolytic anaemia diagnosed

A

Diagnosis by:

  1. Finding spherocytes and increased reticulocyte count
  2. Detecting Ig + complement on RBC surface
  3. Detecting antibodies to RBC antigens / other autoantibodies in the plasma
29
Q

How is autoimmune haemolytic anaemia treated

A
  1. Corticosteroids and immunosuppressive agents

2. Splenectomy if severe cases

30
Q

How is microangiopathic haemolytic anaemia treated

A
  1. Removing the cause (e.g. treating hypertension or stopping causative drug)
  2. Plasma exchange when it is caused by an antibody that leads to fibrin deposition
31
Q

Microcytic anaemia is likely to be due to?

A

Iron deficiency

32
Q

Polycythaemic patient with Red urine. Most likely due to?

A

Renal carcinoma

Haemoglobinuria indicated haemolysis

Polycythaemia rules out haemolysis

Haematuria = RBC in urine

Haemoglobinuria = Hb in urine

Year 2 Collin (114 decks)

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