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I need to learen > Anaemia > Flashcards

Anaemia Flashcards

1
Q

What is anaemia

A

Reduction in the 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

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2
Q

What in a FBC is reduced in anaemia

A

Hb

Usually RBC and Hct

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3
Q

Describe the general pathogenesis of anaemia

A

Reduction in the absolute amount of haemoglobin in the blood stream
Occasionally due to an increase in volume plasma (cannot persist as excess fluid is excreted)

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4
Q

Give an latrogenic cause of anaemia

A

giving too much IV fluid too fast

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5
Q

What are the mechanisms of anaemia

A

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

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6
Q

What are the causes of microcytic anaemia

A

Defect in haem synthesis

  • iron deficiency
  • anaemia of chronic disease

Defect in global synthesis (thalassaemia)

  • Defect in α chain synthesis
  • Defect in β chain synthesis
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7
Q

What is macrocytic anaemia

A

Average cell size is increased

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8
Q

Describe the general pathogenesis of macrocytic anaemia

A

Usually abnormal haemopoiesis

The red cell precursors continue to synthesise haemoglobin and other cellular proteins but fail to divide normally

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9
Q

What are the two types of causes of macrocytic anaemia

A

Premature release of RBCs from bone marrow

Megaloblastic erythropoiesis

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10
Q

Describe the premature release of RBCs in macrocytic anaemia and what might cause it

A

Reticulocytes are 20% larger than mature RBCs

Excess haemolysis
Recent major haemorrhage (if the body has plentiful iron stores)

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11
Q

What is a megaloblast

A

Abnormal bone marrow erythroblast (RBC precursors)

Larger than normal

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12
Q

What occurs in megaloblastic erythropoiesis

A

Maturation of the nucleus is delayed but the cell keeps on growing and synthesising protein in the meantime (nuclei-cytoplasmic dissociation)

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13
Q

What are the common causes of megaloblastic anaemia

A

Vitamin B12 or folic acid deficiency
Drugs interfering with DNA synthesis
Liver disease
Ethanol/alcohol toxicity

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14
Q

What are the mechanisms of normocytic anaemia

A

Recent blood loss
Failure of production of red cells
Pooling of red cells in the spleen

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15
Q

What can cause haemorrhage that causes normocytic anaemia

A
  • trauma
  • peptic ulcer
  • oesophageal varices
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16
Q

What can cause failure of RBC production (normocytic anaemia)

A

Renal failure - lack of erythropoietin
Early stage iron deficiency or anaemia of chronic disease (ACD)
Bone marrow suppression

17
Q

What can cause pooling of RBCs in the spleen

A

portal hypertension

Hypersplenism e.g. portal cirrhosis

18
Q

What is haemolytic anaemia and what can it be due to

A

Anaemia resulting from shortened survival of red cells in the circulation

May be due to intrinsic abnormality of the red cells or extrinsic factors acting on normal red cells

19
Q

What is the difference between inherited and acquired haemolytic anaemia

A

Inherited - can result from abnormalities in the cell membrane, haemoglobin or enzymes in the red cell

Acquired - usually results from extrinsic factors such as micro-organisms, chemicals or drugs that damage the red cell

20
Q

What is the difference between intravascular and extravascular haemolysis

A

Haemolysis is partly intravascular and partly extravascular

Intravascular - if there is very acute damage to the red cell

Extravascular - Defective red cells are removed by the spleen

21
Q

Give examples of causes of inherited haemolytic anaemia

A

Defective:
Cell membrane - Hereditary spherocytosis

Haemoglobin - Sickle cell

Glycolysis - pyruvate kinase deficiency

Enzymes of pentose shunt - G6PD deficiency

22
Q

Give examples of causes of acquired haemolytic anaemia

A

Damage to:
Cell membrane - Autoimmune haemolytic anaemia or snake bite
Whole cell - Microangiopathic haemolytic anaemia, malaria

Damage caused by:
Oxidant exposure - dapsone or primaquine
microorganisms - malaria

23
Q

What is the role of glucose-6-phosphate dehydrogenase

A

G-6-P dehydrogenase is an important enzyme in the pentose phosphate shunt
It is crucial for protecting the RBC from oxidative damage

24
Q

What can cause oxidant damage

A

Broad beans, naphthalene (in moth balls)

Dapsone or primaquine (drugs).

25
Q

What does a deficiency in glucose-6-phosphate dehydrogenase lead to

A

Increases vulnerability to oxidants

It causes intermittent, severe intravascular haemolysis due to infection or oxidant exposure.

26
Q

What kind of cells may be found in the blood in glucose-6-phosphate dehydrogenase deficiency

A

Irregularly contracted cells
Hb is denatured and forms around inclusions called Heinz bodies which can be detected
The spleen removes Heinz bodies, leaving defective RBCs.

27
Q

Which sex does glucose-6-phosphate dehydrogenase deficiency affect more and why

A

The G6PD gene is on the X chromosome, so men are more frequently affected than women.

28
Q

What does autoimmune haemolytic anaemia result from

A

Autoantibodies specific to RBC antigens

29
Q

Explain how the presence autoantibodies for RBC antigens lead to anaemia

A

Splenic macrophages recognise the antigen-antibody complex and remove it along with part of the cell membrane, leading to spherocytosis.
The spherocytes then get removed by the spleen, causing the anaemia.

30
Q

How is autoimmune haemolytic anaemia diagnosed

A

Spherocytes found
Increased reticulocyte count
Immunoglobulin and complement on red cell surface detected
Antibodies to red cell antigens or other autoantibodies in the plasma detected

31
Q

How is autoimmune haemolytic anaemia treated

A

Immunosuppression (e.g. with steroids)

Splenectomy for severe cases

32
Q

Describe hereditary spherocytosis

A

Haemolytic anaemia or chronic compensated haemolysis resulting from an inherited intrinsic defect of the red cell membrane
After entering the circulation the cells lose membrane in the spleen and thus become spherocytic

33
Q

How does hereditary spherocytosis lead to jaundice

A

Spherocytes are less flexible and are removed prematurely by the spleen (extravascular haemolysis)
The bone marrow responds nay increasing output of red cells, leading to polychromasia and reticulocytosis
Leads to increased bilirubin production, jaundice and gall stones

34
Q

What is the osmotic fragility test

A

Spherocytes are more prone to haemolyse when osmotic pressure is reduced

35
Q

How is hereditary spherocytosis treated

A

Splenectomy
Good diet so secondary folic acid deficiency does not occur
One folic acid tablet taken daily

I need to learen (23 decks)

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