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Haematology > 3. Anaemia and polycythaemia > Flashcards

3. Anaemia and polycythaemia Flashcards

1
Q

What is anaemia?

A
  • Reduction in the amount of haemoglobin in a given volume of blood
  • RBC and PCV/Hct usually also reduced
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2
Q

Why can’t anaemia resulting from an increase in plasma volume persist in a healthy person, but can in a sick patient?

A
  • Excess fluid excreted when healthy

* Fluid retention possible in sick patients, which lowers the Hb

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3
Q

What are the mechanisms of anaemia?

A
  • Reduced production of red cells/Hb in the bone marrow
  • Loss of blood from the body
  • Reduced survival in the circulation
  • Pooling of red cells in a very large spleen
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4
Q

What can reduce the synthesis of haem?

A
  • Iron deficiency
  • Acute/chronic inflammation - delivery of iron from the bone marrow macrophage to the developing red cell is interfered with
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5
Q

Which inherited defect can lead to a reduced synthesis of globin?

A

Thalassaemia

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6
Q

What are the common causes of microcytic anaemia?

A
  • Defect in haem synthesis
  • Defect in globin synthesis
  • Iron deficiency
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7
Q

What are the causes of macrocytic anaemia?

A
  • Lack of vitamin B12 or folic acid
  • Abnormal haemopoeisis
  • RBC precursors continue to synthesise haemoglobin and other cellular proteins
  • Red cells fail to divide normally - end up larger than normal
  • Megaloblastic erythropoiesis - delay in maturation of the nucleus, while the cytoplasm continues to mature (nucleocytoplasmic dissociation)
  • Premature release from bone marrow - reticulocytes are about 20% larger
  • Drugs
  • Liver disease and ethanol toxicity
  • Major blood loss - reticulocytes increased
  • Haemolytic anaemia - reticulocytes increased
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8
Q

What is a megaloblast?

A
  • Abnormal bone marrow erythroblast

* Larger than normal and shows nucleocytoplasmic dissociation

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9
Q

How can you detect megaloblastic anaemia?

A
  • Peripheral blood features

* Bone marrow examination more accurate

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10
Q

What are the causes of normochromic anaemia?

A

• Peptic ulcer, oesophageal varices, trauma
• Failure of production of red cells:
- iron deficiency
- renal failure
- bone marrow suppression/failure - cancer treatment
- bone marrow infiltration - cancer metastases
• Hypersplenism

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11
Q

What is haemolytic anaemia?

A
  • Shortened survival of red cells
  • Bone marrow cannot compensate
  • Can result from intrinsic abnormality or extrinsic factors
  • Can be inherited or acquired
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12
Q

What can inherited and acquired haemolytic anaemia result in?

A
  • Inherited - abnormalities in the cell membrane, haemoglobin or enzymes
  • Acquired - microorganisms, chemicals or drugs can damage the red cell membrane, or whole cell
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13
Q

What is the difference between intravascular and extravascular haemolysis?

A
  • Intravascular - very acute damage to the red cell

* Extravascular - defective red cells are removed by the spleen

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14
Q

What happens to red cells if there is an abnormal cell membrane or haemoglobin or a defect in the glycolytic pathway

A

They can burst

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15
Q

How does Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency affect red cells?

A
  • G6PD is an enzyme involved in the pentose phosphate pathway
  • Metabolic parallel to glycolysis that generates NADPH and pentoses
  • Only source of reduced glutathione in red cells
  • G6PD offers protection to red cells from oxidising free radicals
  • In people with G6PD deficiency, risk of haemolytic anaemia in states of oxidative stress
  • Usually causes intermittent, severe intravascular haemolysis
  • Haemoglobin is denatured and forms round inclusions - Heinz bodies (can get more than one Heinz body in a cell)
  • Heinz bodies are removed by the spleen, leaving a defect in the cell
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16
Q

How does pyruvate kinase deficiency affect red cells?

A
  • Pyruvate kinase is involved in the last stage of glycolysis
  • Deficiency => cell with decreased energy
  • Can’t synthesise ATP - cell dies
17
Q

When should you suspect haemolytic anaemia?

A
  • Unexplained (normochromic and either normocytic or macrocytic)
  • Evidence of morphologically abnormal red cells
  • Evidence of increased red cell breakdown (increased lactate DH, increased unconjugated bilirubin)
  • Evidence of increased bone marrow activity
18
Q

What does jaundice in sickle cell anaemia reflect?

A

Blood cell breakdown

19
Q

What can increased bilirubin excretion in children with haemolytic anaemia lead to?

A

Gall stones

20
Q

What is hereditary spherocytosis?

A
  • Haemolytic anaemia or chronic compensated haemolysis
  • Resulting from an inherited instrinsic defect of the red cell membrane
  • Loss of membrane in the spleen
  • Become more spherical - trapped in spleen - removed by splenic macrophages (extravascular haemolysis)
  • Bone marrow responds - increased output - polychromasia + reticulocytosis
  • Still have increased red cell breakdown - subject to jaundice and gall stones
21
Q

How can hereditary spherocytosis be treated?

A
  • Splenectomy in severe cases
  • Good diet to avoid secondary folic acid deficiency
  • Folic acid tablet daily
22
Q

Who does G6PD deficiency usually affect?

A
  • Gene is on the X chromosome

* So usually hemizygous males, but occasionally

23
Q

What is autoimmune haemolytic anaemia?

A
  • Production of autoantibodies directed at RBC antigens
  • The immunoglobin bound to the red cell membrane is recognised by splenic macrophages
  • These remove parts of the red cell membrane
  • Spherocytosis
24
Q

What is it about the spherocytes that lead to their removal by the spleen?

A
  • Immunoglobin can also have complement components bound
  • They are less flexible than normal red cells
  • The combination of cell rigidity and recognition of antibody and complement on the surface leads to removal
25
Q

How can you diagnose spherocytosis?

A

• Finding spherocytes and an increased reticulocyte count
• Detecting immunoglobin (with our without complement)
on the red cell surface
• Detecting antibodies to red cell antigens, or other autoantibodies in the plasma

26
Q

How can spherocytosis be treated?

A
  • Corticosteroids and other immunosuppressive agents

* Splenoctomy for severe cases

27
Q

What are 2 of the causes of spherocytosis?

A
  • Hereditary Spherocytosis

* Autoimmune haemolytic anaemia

28
Q

How will haemolysis affect urine?

A
  • Dark urine

* Lots of bilirubin

29
Q

What is polycythaemia?

A
  • Abnormally increased concentration of haemoglobin in the blood
  • Reduction of plasma volume or increase in red cell numbers
30
Q

A patient has polycythaemia and noticed blood in his urine, what is the likely cause?

A

Renal carcinoma

Haematology (11 decks)

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