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Haematology > Red Cells > Flashcards

Red Cells Flashcards

1
Q

What substances are required for red cell production?

A

Iron
B12
Folic acid
Erythropoietin

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2
Q

Where does red cell breakdown occur?

A

Spleen

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3
Q

What system is involved in red cell breakdown?

A

Reticuloendothelial system

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4
Q

Red cell life span

A

120 days

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5
Q

What is bilirubin bound to in the plasma?

A

Albumin

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6
Q

What is haem?

A

The part of haemoglobin containing iron

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7
Q

What is contained in the mature red blood cell?

A

Membrane
Enzymes
Haemoglobin

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8
Q

Where are genetic defects described in the RBC?

A

Red cell membrane
Metabolic pathways (enzymes)
Haemoglobin

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9
Q

Which proteins are responsible for maintaining red cell shape and deformability?

A

Skeletal proteins

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10
Q

What can defects in skeletal proteins can lead to?

A

Increased cell destruction

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11
Q

What is hereditary spherocytosis?

A

Red cells are spherical
Removed from circulation by the RE system (extravascular)
Most commonly autosomal dominant
Defects in 5 different structural proteins

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12
Q

Presentation of hereditary spherocytosis

A

Anaemia
Jaundice (neonatal)
Splenomegaly
Pigment gallstones

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13
Q

Treatment of hereditary spherocytosis

A

Folic acid (increased requirements)
Transfusion
Splenectomy if anaemia very severe

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14
Q

Membrane disorders

A

Hereditary spherocytosis
Hereditary Elliptocytosis (rather than spheres)
Hereditary Pyropoikilocytosis (all different sizes)
South East Asian Ovalocytosis

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15
Q

What is the function of glycolysis?

A

Provides energy

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16
Q

What are the enzyme pathways used by red cells?

A

Glycolysis

Pentose Phosphate shunt

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17
Q

What is the function of the pentose phosphate shunt (/Glucose 6 Phosphate Dehydrogenase (G6PD))?

A

Protects cell proteins (haemoglobin) from oxidative damage

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18
Q

Why is G6PD deficiency common?

A

Confers protection against malaria

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19
Q

What is G6PD deficiency?

A

Commonest disease causing enzymopathy in the world
Cells vulnerable to oxidative damage
X Linked

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20
Q

Presentation of G6PD deficiency

A

Variable degrees of anaemia
Neonatal Jaundice
Splenomegaly
Pigment Gallstones

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21
Q

What is pyruvate kinase deficiency?

A

Reduced ATP - glycolytic pathway
Increased 2,3-DPG
Cells rigid

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22
Q

When does haemoglobin give up oxygen to tissues?

A

Decreased pH
Increased temperature
Increased CO2

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23
Q

What are the normal proportions of adult Hb?

A 
Adult haemoglobin (HbA) composed of haem molecule and:
Hb A  (αααα)  – 97% - 4 alpha chains
Hb A2 (ααδδ) – 2% - 2 alpha, 2 delta
Hb F  (ααγγ)  – 1% (foetal Hb) - 2 alpha, 2 gamma
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24
Q

Haemoglobinopathies

A

Inherited abnormalities of haemoglobin synthesis
Reduced or absent globin chain production (thalassaemia)
Mutations leading to structurally abnormal globin chain (sickle cell disease)

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25
Q

What is the sickle cell disease composition?

A

Sickle haemoglobin (HbS) composed of haem molecule and
2 α chains
2 β (sickle) chains

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26
Q

Consequences of HbS Polymerisation

A

Red cell injury, cation loss, dehydration => haemolysis
=> Endothelial activation
Promotion of inflammation
Coagulation activation
Dysregulation of vasomotor tone by vasodilator mediators (NO) => vaso-occlusion

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27
Q

Sickle cell presentation

A 
Painful Vaso-occlusive crises
   - Bone
Chest Crisis
Stroke
Increased infection risk
   - Hyposplenism 
Chronic haemolytic anaemia
   - Gallstones
   - Aplastic crisis
Sequestration crises
   - Spleen
   - Liver
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28
Q

Management of sickle cell disease

A 
Life long prophylaxis
   - Vaccination
   - Penicillin (and malarial) prophylaxis	
   - Folic acid
Acute Events
   - Hydration 
   - Oxygenation
   - Prompt treatment of infection
   - Analgaesia (opiates, NSAIDs)
   - Blood transfusion
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29
Q

Disease modifying drugs in sickle cell disease

A

Hydroxycarbamide

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30
Q

What is thalassaemia?

A

Reduced or absent globin chain production

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31
Q

Homozygous alpha zero thalassaemia (α0/α0 )

A

No alpha chains

Hydrops Fetalis – incompatible with life

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32
Q

Beta thalassaemia major (Homozygous beta thalassaemia)

A

No beta chains

Transfusion dependent anaemia

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33
Q

Thalassaemia minor (common)

A

“Trait” or carrier state

Hypochromic microcytic red cell indices

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34
Q

Beta thalassaemia major

A

Severe anaemia

  • Present at 3-6 months of age
  • Expansion of ineffective bone marrow
  • Bony deformities
  • Splenomegaly
  • Growth retardation

Life expectancy untreated or with irregular transfusions <10 years

35
Q

Beta thalassaemia major treatment

A

4-6 weekly blood transfusions

Causes iron overload so chelation therapy required

36
Q

Chelation agents

A

Removes excess iron
DFO
DFP
DFX

37
Q

Sideroblastic anaemia

A

Defects in mitochondrial steps of haem synthesis
ALA synthase mutations
Hereditary
Aquired – (most common) a form of myelodysplasia

38
Q

General clinical features of anaemia due to reduced oxygen delivery to tissues

A 
Tiredness/pallor
Breathlessness
Swelling of ankles
Dizziness
Chest pain
39
Q

What are the overall causes of anaemia?

A

Bone marrow
Red cell
Destruction/loss

40
Q

Causes of anaemia involving the bone marrow

A

Cellularity
Stroma
Nutrients

41
Q

Causes of anaemia involving the red blood cells

A

Membrane
Haemoglobin
Enzymes

42
Q

Causes of anaemia involving destruction/loss

A

Blood loss
Haemolysis
Hypersplenism

43
Q

What are red cell indices

A

Automated measurement of red cell size and haemoglobin content

44
Q

MCH

A

Mean cell haemoglobin

45
Q

MCV

A

Mean cell volume (cell size)

46
Q

Morphological descriptions of anaemia

A

Hypochromic, microcytic
Normochromic, normocytic
Macrocytic

47
Q

Blood film required for hypochromic, microcytic

A

Serum ferritin

48
Q

Blood film required for normochromic, normocytic

A

Reticulocyte count

49
Q

Blood film required for macrocytic anaemia

A

B12/folate

Bone marrow

50
Q

Diagnosis for low serum ferritin in hypochromic microcytic anaemia

A

Iron deficiency

51
Q

Diagnosis for normal or increased serum ferritin in hypochromic microcytic anaemia

A

Thalassaemia secondary anaemia

52
Q

What happens to absorbed iron in the body?

A

Bound to mucosal ferritin or
Transported across the basement membrane by ferroportin

Then bound to transferrin in plasma

Stored as Ferritin - mainly in liver

53
Q

What is hepcidin

A

Reduces intestinal iron absorption and mobilisation from reticuloendothelial cells

Synthesised in hepatocytes in response to ↑iron levels and inflammation

54
Q

What is the commonest cause of anaemia?

A

Iron deficiency

55
Q

Clinical features of iron deficiency

A

Koilonychia
Atrophic tongue
Angular cheilitis

56
Q

Causes of iron deficiency

A 
GI blood loss
Menorrhagia
Malabsorption
	- gastrectomy
	- coeliac disease
57
Q

Diagnosis for normal/low reticulocyte count in normochromic normocytic anaemia

A

Secondary anaemia
Hypoplasia
Marrow infiltration

58
Q

Diagnosis for increased reticulocyte count in normochromic normocytic anaemia

A

Acute blood loss

Haemolysis

59
Q

What is secondary anaemia?

A

“Anaemia of chronic disease”

Mainly normochromic normocytic, also hypochromic microcytic

60
Q

Why is there a decreased haemoglobin in haemolytic anaemia?

A

Accelerated cell destruction

61
Q

Why is there an increase in reticulocyte count in haemolytic anaemia?

A

Compensation by bone marrow as a result of the decreased haemoglobin

62
Q

What is the reticulocyte count?

A

measures how fast reticulocytes are made by the bone marrow and released into the blood

63
Q

What are reticulocytes?

A

Immature red blood cells

64
Q

Congenital causes of haemolytic anaemia

A 
Hereditary spherocytosis (HS)
Enzyme deficiency (G6PD deficiency)
Haemoglobinopathy (HbSS)
65
Q

Extravascular acquired causes of haemolytic anaemia

A

Auto-immune haemolytic anaemia

66
Q

Intravascular acquired causes of haemolytic anaemia

A

Mechanical eg.artificial valve
Severe infection/DIC
PET/HUS/TTP

67
Q

TTP

A

Thrombotic thrombocytopenia purpura

68
Q

What is the purpose of the direct antiglobulin test?

A

Detects antibody or complement on red cell membrane

Implies immune basis for haemolysis

69
Q

What does the reagent in a direct antiglobulin test contain?

A

Anti-human IgG

Anti-complement

70
Q

Haemolytic anaemia management

A

Support marrow function
- Folic acid
Correct cause
- Immunosuppression if autoimmune
- Remove site of red cell destruction (splenectomy)
- Treat sepsis, leaky prosthetic valve, malignancy etc. if intravascular
Consider transfusion

71
Q

What are the possible results of a B12/folate assay?

A

Megaloblastic

Non-megaloblastic

72
Q

Megaloblastic macrocytic anaemia causes

A

B12 deficiency

Folate deficiency

73
Q

Non-megaloblastic macrocytic anaemia causes

A

Myelodysplasia
Marrow infiltration
Drugs

74
Q

What does dietary B12 bind to?

A

Intrinsic factor

75
Q

Which cells secrete intrinsic factor?

A

Gastric parietal cells

76
Q

What binds to B12, where and why?

A

Transcobalamin II
In portal circulation
For transport to marrow and other tissues

77
Q

Presentation of megaloblastic anaemia

A

“Lemon yellow” tinge
Bilirubin, LDH
Red cells friable

78
Q

What is pernicious anaemia?

A

Autoimmune disease
Antibodies against intrinsic factor (diagnostic) or
gastric parietal cells (less specific)
Malabsorption of dietary B12

79
Q

Megaloblastic anaemia treatment

A

Replace vitamin

B12 deficiency - B12 IM injection

Folate deficiency - oral folate supplement (ensure B12 normal if neuropathic symptoms)

80
Q

Other causes of macrocytosis

A 
Alcohol
Drugs (Methotrexate, Antiretrovirals, hydroxycarbamide)
Disordered liver function
Hypothyroidism
Myelodysplasia
81
Q

What is aplastic anaemia?

A

Autoimmune disease in which the body fails to produce blood cells in sufficient numbers
Deficiency of all blood cell types

82
Q

What is aplastic crisis?

A

The body does not make enough new red blood cells to replace the ones that are already in the blood

83
Q

What is the commonest cause of a macrocytosis?

A

Liver disease

Haematology (18 decks)

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