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Year 2 - BRS > 5.18 - Anaemia and transfusion > Flashcards

5.18 - Anaemia and transfusion Flashcards

1
Q

What are the four underlying mechanisms of anaemia?

A
  • reduced production of red cells/haemoglobin by the bone marrow
  • reduced survival of red cells in circulation (haemolysis)
  • loss of blood from the body
  • pooling of red cells in a very large spleen
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2
Q

What are spherocytes?

A

Very round cells without the usual central pallor (which reflects the disc shape of a normal RBC)

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3
Q

What is hereditary spherocytosis?

A
  • due to an inherited defect in red cell membrane
  • disruption of vertical linkages in membrane, usually ankyrin/spectrin
  • defect in membrane can lead to haemolysis
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4
Q

What is the difference between haemolysis and haemolytic anaemia?

A
  • haemolysis - increased destruction of red blood cells (reduced RBC survival)
  • haemolytic anaemias - group of anaemias due to reduced red cell lifespan (haemolysis that leads to a reduction in Hb)
  • haemolytic anaemia is the result of haemolysis
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5
Q

What term describes a patient with anaemia due to haemolysis?

A

Haemolytic anaemia

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6
Q

How is haemolytic anaemia treated? (2)

A
  • folic acid (because of the increased requirement for erythropoiesis to replace lost RBCs)
  • splenectomy (if severe) to increase red cell life span
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7
Q

What is the bone marrow response to haemolysis?

A

Reticulocytosis - increases production of young red cells - reticulocytes (seen as larger and bluer polychromatic macrocytes due to increased RNA content)

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8
Q

How do we interpret an increase in unconjugated bilirubin?

A

Haemolytic jaundice - RBC breakdown causes increased unconjugated BR in bloodstream

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9
Q

What is formed as a result of increased breakdown of haemoglobin to bilirubin?

A

Gallstones

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10
Q

What is it called when a gallstone obstructs the common bile duct?

A

Obstructive jaundice - liver still able to conjugate bilirubin but not passing from bile ducts and gall bladder into the duodenum (high conjugated bilirubin)

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11
Q

What finding is common in haemolytic anaemia?

A

Pigment gallstones

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12
Q

What are the differences between unconjugated vs conjugated bilirubin? (5)

A
  • insoluble in blood vs water soluble
  • largely attached to albumin in blood vs small amounts are loosely bound to albumin in blood
  • accumulates in pre-hepatic jaundice vs accumulates in post-hepatic jaundice
  • toxic to tissues and organs e.g. brain vs relatively non-toxic
  • cannot be excreted in urine vs can be excreted in urine (dark urine)
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13
Q

What is DAT?

A

Direct antiglobulin test (i) - detects antibodies bound to antigen on RBC membrane in a patient who has developed an autoantibody

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14
Q

What is autoimmune haemolytic anaemia (AIHA)?

A
  • DAT positive
  • can be idiopathic
  • or, associated with disorders of immune system:
    • systemic autoimmune disease (SLE)
    • underlying lymphoid cancers (lymphoma)

Host immune response against RBC antigens

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15
Q

What are the blood count abnormalities in autoimmune haemolytic anaemia? (7)

A
  • low Hb
  • high MCV
  • high reticulocytes
  • high unconjugated bilirubin
  • high LDH
  • +++ DAT
  • spherocytes on blood film

High MCV is due to reticulocytosis

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16
Q

What is laboratory evidence of haemolysis? (3 + 1)

A
  • LDH raised
  • unconjugated hyperbilirubinaemia (anaemia with raised bilirubin)
  • reduced haptoglobins
  • (raised reticulocytes)
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17
Q

Are acquired anaemias due to a defect in the RBC or a problem/defect in the RBC environment?

A

RBC environment defect - plasma/vasculature

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18
Q

What are non-immune environmental factors that can damage RBCs? (5)

A
  • microangiopathic
  • haemolytic uraemic syndrome
  • malaria
  • snake venom
  • drugs
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19
Q

What are immune mediated (DAT +ve) environmental factors that can damage RBCs? (2)

A
  • autoimmune
  • alloimmune (post blood transfusion)
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20
Q

What two blood disorders are spherocytes present in?

A
  • hereditary spherocytosis
  • acquired autoimmune haemolytic anaemia
  • (distinguished by DAT test)
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21
Q

When do we consider haemolysis?

A
  • anaemia with raised bilirubin
    • elevated reticulocytes/LDH/unconjugated BR
    • blood film
  • clinical history and examination may point to acquired or inherited (e.g. sickle cell)
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22
Q

In acquired haemolysis, what does DAT positive confirm?

A
  • confirms immune mechanism
    • systemic autoimmune disease
    • underlying lymphoid cancer (lymphoma)
    • idiopathic

e.g. autoimmune haemolytic anaemia

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23
Q

What are examples of acquired red cell defects? (3)

A
  • damage to red cell membrane e.g. AIHA or snake bite
  • damage to whole red cell e.g. MAHA (microangiopathic haemolytic anaemia)
  • oxidant exposure, damage to red cell membrane and Hb e.g. dapsone or primaquine
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24
Q

What are examples of inherited red cell defects? (4)

A
  • abnormal RBC membrane e.g. hereditary spherocytosis
  • abnormal Hb e.g. sickle cell anaemia
  • defects in glycolytic pathway e.g. pyruvate kinase deficiency
  • defect in enzymes of pentose shunt e.g. G6PD deficiency
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25
Q

What does the glycolytic pathway do?

A

Provides energy for the cell

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26
Q

What does the pentose shunt do?

A

Protects the cell from oxidant damage - G6PD is a key enzyme (deficiency is very common)

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27
Q

What are the similarities and differences between irregularly contracted cells and spherocytes?

A
  • both have lost their central pallor
  • but they differ as irregularly contracted cells are more irregularly shaped
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28
Q

What is visible in a blood film of G6PD deficiency? (4)

A
  • ghost cells
  • hemighost cells
  • Heinz bodies
  • irregularly contracted cells
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29
Q

What features on a blood film shows oxidant damage? (2)

A
  • irregularly contracted cells
  • Heinz bodies
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30
Q

What are Heinz bodies?

A

Precipitated oxidised haemoglobin

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31
Q

What do ‘ghost cells’ show us?

A

‘Ghost cells’ show that there has been intravascular haemolysis

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32
Q

What should a patient with G6PD deficiency be advised to do? (4)

A
  • avoid oxidant drugs
  • avoid eating broad beans (fava beans)
  • avoid naphthalene
  • be aware that haemolysis can result from infection
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33
Q

How can G6PD deficiency cause haemolysis?

A
  • G6PD is an important enzyme in the hexose monophosphate shunt, which is tightly coupled to glutathione metabolism, which protects red cells from oxidant damage
  • oxidants may be generated in the bloodstream, e.g. during infection, or may be exogeneous e.g. drugs, broad beans
  • a deficiency in G6PD causes red cells to be vulnerable to oxidant damage, resulting in haemolysis
34
Q

What is haemolytic anaemia?

A

Anaemia resulting from shortened survival of red cells in the circulation

35
Q

What two types of abnormalities can haemolysis result from?

A
  • haemolysis can result from an intrinsic abnormality of the red cells
  • haemolysis can result from extrinsic factors acting on normal red cells
36
Q

How can haemolytic anaemia be classified? (4)

A
  • inherited
  • acquired
  • intravascular
  • extravascular
37
Q

What is the difference between inherited and acquired haemolytic anaemia?

A
  • inherited haemolytic anaemia can result from abnormalities in the cell membrane, the haemoglobin or the enzymes in the red cell
  • acquired haemolytic anaemia usually results from extrinsic factors such as microorganisms, chemicals or drugs that damage the red cell
  • extrinsic factors can interact with red cells that have an intrinsic abnormality
38
Q

What is the difference between intravascular and extravascular haemolytic anaemia?

A
  • intravascular haemolysis occurs if there is very acute damage to the cell
  • extravascular haemolysis occurs when defective red cells are removed by the spleen
  • often haemolysis is partly intravascular and partly extravascular
39
Q

What can oxidant exposure to red cells cause?

A

Oxidant exposure (acquired cause) –> precipitation of episodic haemolysis in individuals with enzyme G6PD deficiency (inherited cause)

40
Q

What makes us think a diagnosis is haemolytic anaemia? (4)

A
  • otherwise unexplained anaemia, which is normochromic and usually either normocytic/macrocytic (severe)
  • evidence of morphologically abnormal red cells (e.g. ghost cells)
  • evidence of increased red cell breakdown (e.g. jaundice due to increased BR)
  • evidence of increased bone marrow activity (reticulocytosis, increased polychromatic macrocytes)
41
Q

Inherited haemolytic anaemia - what condition is caused by a membrane defect?

A

Hereditary spherocytosis

42
Q

Inherited haemolytic anaemia - what condition is caused by a haemoglobin defect?

A

Sickle cell anaemia

43
Q

Inherited haemolytic anaemia - what condition is caused by a glycolytic pathway defect?

A

Pyruvate kinase deficiency (rare)

44
Q

Inherited haemolytic anaemia - what condition is caused by a pentose shunt defect?

A

Glucose-6-phosphate dehydrogenase deficiency

45
Q

Acquired haemolytic anaemia - what condition is caused by a membrane defect (immune)?

A

Autoimmune haemolytic anaemia (AIHA)

46
Q

Acquired haemolytic anaemia - what condition is caused by a whole red cell defect (mechanical)?

A

Microangiopathic haemolytic anaemia (MAHA)

47
Q

Acquired haemolytic anaemia - what condition is caused by a whole red cell defect (oxidant)?

A

Drugs and chemicals

48
Q

Acquired haemolytic anaemia - what condition is caused by a whole red cell defect (microbiological)?

A

Malaria

49
Q

What are the blood count abnormalities in someone with iron deficiency anaemia? (11)

A
  • low Hb
  • low MCV
  • low MCH
  • low MCHC
  • low RBC
  • high platelets
  • low ferritin
  • low serum iron
  • high transferrin
  • low transferrin saturation
  • Hb electrophoresis - no increase in HbA2 (not beta thalassaemia)
50
Q

What are some further questions to ask someone with iron deficiency anaemia? (5)

A
  • diet - vegetarian/vegan
  • gastrointestinal symptoms - dysphagia/dyspepsia/abdominal pain/change in bowel habit/haematemesis/rectal bleeding/melaena
  • menstrual history/post-menopausal bleeding
  • weight loss
  • medication - e.g. aspirin/NSAIDs
51
Q

What are three clinical signs of iron deficiency anaemia?

A
  • koilonychia
  • glossitis
  • angular stomatitis

Angular stomatitis/cheilitis = irritated corners of mouth

52
Q

What further tests can be done after diagnosis of iron deficiency anaemia? (3)

A
  • investigating for blood in stool - faecal immunochemical test (FIT)
  • gastrointestinal (GI) investigations - upper GI endoscopy (oesophagus, stomach, duodenum), take duodenal biopsy, colonoscopy
  • coeliac antibody testing
53
Q

What are the causes of iron deficiency anaemia? (3)

A
  • increased blood loss - commonest cause in adults
    • hookworm commonest cause worldwide
    • menstrual (menorrhagia)
    • GI (often occult)
  • insufficient iron intake
    • dietary - vegetarians
    • malabsorption - coeliac disease (gluten-induced enteropathy), H.pyloris gastritis
  • increased iron requirements
    • physiological - pregnancy, infancy
54
Q

What are blood film features of iron deficiency anaemia? (4)

A
  • microcytosis (low MCV, small cells)
  • hypochromia (low MCHC, pale cells)
  • occasional target cells
  • elliptocytes (pencil cells)
55
Q

What does reduced ferritin cause? (2)

A
  • reduces hepcidin production
  • increases iron supply
56
Q

What is absorption of iron from the gut and release of storage iron increased by?

A

Reduced hepcidin

57
Q

How do you treat iron deficiency anaemia?

A

Iron replacement therapy (e.g. ferrous sulphate tablets)

58
Q

What differential diagnoses are available for anaemia associated with low MCV? (3)

A
  • iron deficiency anaemia
  • thalassaemia
  • anaemia of chronic disease
59
Q

What is the difference in blood count results between iron deficiency anaemia vs anaemia of chronic disease?

A
  • MCV: low vs low/normal
  • ferritin: low vs high
  • transferrin: high vs low/normal
  • transferrin saturation: low vs normal
  • ESR: may be high (due to low Hct) vs high
60
Q

What are the features on a blood film of someone with anaemia of chronic disease? (3)

A
  • hypochromic
  • microcytic
  • Rouleaux (stacks of RBCs)
61
Q

Does a normal ferritin always exclude iron deficiency?

A

No - ferritin can be normal if you have both iron deficiency anaemia and anaemia of chronic disease

62
Q

Why does anaemia of chronic disease happen?

A
  • hepcidin is usually secreted by liver in response to high iron states
  • hepcidin production is also increased in inflammatory states, reducing iron supply (blocks absorption of iron from gut and release of storage iron)
63
Q

What are some common causes of anaemia of chronic disease? (3)

A
  • infections such as TB and HIV
  • rheumatoid arthritis and other autoimmune disorders
  • malignancy
64
Q

How do you treat anaemia of chronic disease?

A

Treat the underlying cause (no obvious cause except the patient is ill)

65
Q

What are the megaloblastic features in the bone marrow in megaloblastic anaemia due to B12 deficiency? (3)

A
  • megaloblasts are large with nucleocytoplasmic dissociation
  • impaired DNA synthesis, nuclear maturation and cell division
  • adequate cytoplasmic maturation and cell growth
66
Q

What can cause megaloblastic change in the bone marrow?

A
  • vitamin B12 and folate
    • required for DNA synthesis
    • absence leads to severe anaemia which can be fatal
  • secondary to agents/mutations that impair DNA synthesis
    • drugs - azathioprine, cytotoxic chemotherapy
    • folate antagonists - methotrexate
    • BM cancers - myelodysplastic syndrome
67
Q

What is vitamin B12 required for? (2)

A
  • DNA synthesis
  • integrity of the nervous system
68
Q

What is folic acid required for? (2)

A
  • DNA synthesis
  • homocysteine metabolism
69
Q

What are the dietary causes of vitamin B12 deficiency and how is this treated?

A
  • B12 present in animal products
  • inadequate diet, veganism
  • treated with oral supplements
70
Q

What are the gastric causes of vitamin B12 deficiency and how is this treated?

A
  • intrinsic factor needed for B12 metabolism
  • gastrectomy (some bariatric procedures); autoimmune (pernicious anaemia - anti-GPC and IF antibodies)
  • treated with hydroxocobalamin injections (IM)
71
Q

What are the bowel causes of vitamin B12 deficiency and how is this treated?

A
  • terminal ileum needed for B12 metabolism
  • Crohn’s disease; ileal resection
  • treated with hydroxocobalamin injections (IM)
72
Q

What are the reduced availability causes of folic acid deficiency and how is this treated?

A
  • dietary - poverty, alcoholism
  • malabsorption - coeliac disease, jejunal resection
  • treated with oral supplements
73
Q

What are the increased demand causes of folic acid deficiency and how is this treated?

A
  • pregnancy
  • lactation
  • increased cell turnover - haemolysis
  • treated with oral supplements
74
Q

What neurological disorders can cause megaloblastic anaemia?

A
  • vitamin B12 - dementia and sub-acute combined degeneration (SACD) of spinal cord
  • folic acid - developmental neural tube defects
75
Q

What is megaloblastic anaemia?

A

Anaemia associated with megaloblastic morphological changes in the bone marrow due to asynchronous nucleocytoplasmic maturation

76
Q

What are the two most common causes of megaloblastic anaemia?

A
  • vitamin B12 deficiency
  • folic acid deficiency
77
Q

What is the general relationship between cell sizes and colours in anaemia?

A
  • microcytic usually hypochromic
  • normocytic and macrocytic usually normochromic
78
Q

What are the common causes of a microcytic anaemia? (2)

A
  • defect in haem synthesis - iron deficiency anaemia, anaemia of chronic disease
  • defect in globin synthesis (thalassaemia) - defect in alpha chain synthesis (a-thalassaemia), defect in beta chain synthesis (b-thalassaemia)
79
Q

What are the mechanisms of normocytic anaemia? (3)

A
  • recent blood loss - GI haemorrhage, trauma
  • failure of production of RBCs - early stages of iron deficiency, BM failure/suppression (e.g. chemo), BM infiltration (e.g. leukaemia)
  • pooling of RBC in spleen - hypersplenism (e.g. liver cirrhosis), splenic sequestration in sickle cell anaemia
80
Q

What are some common causes of macrocytic anaemia? (4)

A
  • lack of vitamin B12/folic acid (megaloblastic anaemia)
  • use of drugs interfering with DNA synthesis
  • liver disease and ethanol toxicity
  • haemolytic anaemia (reticulocytes increased)

Year 2 - BRS (84 decks)

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