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Immunology and Haematology > Red Cells 1 > Flashcards

Red Cells 1 Flashcards

1
Q

What is anaemia?

A

Anaemia = reduction in red cells or their haemoglobin content

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2
Q

Describe the aetiologies of anaemia?

A
  • Blood loss
  • Increased destruction
  • Lack of production
  • Defective production
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3
Q

Where are red cells produced?

A

Bone marrow

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4
Q

Describe the development of red cells?

A

1) Stem cell - haemocytoblast
2) Committed cell - proerythroblast
3) Developmental pathway: phase 1, 2 and 3
4) Erythrocyte

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5
Q

What are some substances required for red cell production?

A
  • Metals
    • Iron, copper, cobalt, manganese
  • Vitamins
    • B12, folic acid, thiamine, vitamin B6, vitamin C, vitamin E
  • Amino acids
  • Hormones
    • Erythropoietin, GM-CSF, androgens, thyroxine
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6
Q

Where does red cell breakdown occur?

A

Occurs in the reticuloendothelial system:

  • Macrophages in spleen, liver, lymph node and other tissues like lungs and guts recognise old red cells and destroy them
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7
Q

What is the normal lifespan of red cells?

A

120 days

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8
Q

Describe how the red cell is recycled when broken down?

A
  • Globin
    • In reticular system amino acids are reutilised
  • Haem
    • Iron recycled into haemoglobin
    • Haem broken down into biliverdin then bilirubin (unconjugated bilirubin)
    • Bilirubin carried bound to albumin
    • Converted into bilirubin glucuronide in liver
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9
Q

What are mature red cells called?

A

Erythrocyte

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10
Q

What do erythrocytes contain?

A
  • Membrane
  • Enzymes
  • Haemoglobin
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11
Q

What shape is an erythrocyte and why?

A
  • Make cell small to squeeze through capillaries
  • Increase surface area for gas transfer
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12
Q

What is the red cell membrane formed from?

A
  • Lipid bilayer
  • Skeletal proteins
    • Responsible for maintaining red cell shape and deformability
    • Defects can lead to increased cell destruction
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13
Q

What are the skeletal proteins on the red cell membrane responsible for?

A
  • Responsible for maintaining red cell shape and deformability
  • Defects can lead to increased cell destruction
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14
Q

What are important red cell pathways?

A
  • Glycolysis
    • Provides energy
  • Pentose phosphate shunt
    • Protects from oxidative damage
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15
Q

What does the pentose phosphate shunt do?

A
  • Protects from oxidative damage
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16
Q

What is an important enzyme used in both glycolysis and pentose phosphate shunt?

A

An enzyme used in both of these pathways is glucose-6-phosphate dehydrogenase:

  • Protects red cell proteins (haemoglobin) from oxidative damage
    • Produces NADPH – vital for reduction of glutathione
    • Reduced glutathione scavenges and detoxifies reactive oxygen species
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17
Q

How does glucose-6-phosphatase protect haemoglobin from oxidative damage?

A
  • Protects red cell proteins (haemoglobin) from oxidative damage
    • Produces NADPH – vital for reduction of glutathione
    • Reduced glutathione scavenges and detoxifies reactive oxygen species
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18
Q

Describe the haemoglobin structure?

A
  • Polypeptide chain
    • 2 beta chains and two alpha chain
  • Haem molecule
    • 4 haem molecules – each associated with one chain
    • Contains iron
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19
Q

What is the polypeptide chain of haemoglobin formed from?

A
  • 2 beta chains and two alpha chain
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20
Q

Each haem molecule is associated with how many chains?

A

Ech associated with one chain

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21
Q

What metal is found in the haem molecule?

A

Iron

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22
Q

How many haem molecules are in haemoglobin?

A
  • 4 haem molecules – each associated with one chain
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23
Q

What is the function of haemoglobin?

A
  • Carries oxygen
    • 2 structures – conformational change to uptake and unload oxygen
      • Oxyhaemoglobin and deoxyhaemoglobin
      • 2,3 – DPG holds deoxyhaemoglobin in tight structure
  • Gas exchange
    • O2 to tissues
    • CO2 to lungs
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24
Q

What are the 2 structures of haemoglobin?

A
  • 2 structures – conformational change to uptake and unload oxygen
    • Oxyhaemoglobin and deoxyhaemoglobin
    • 2,3 – DPG holds deoxyhaemoglobin in tight structure
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25
Q

What molecule holds deoxyhaemoglobin in tight structure?

A

2-3 - DPG

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26
Q

Describe the oxygen dissociation curve?

A
  • Shifts as compensatory mechanism
  • “Bohr effect”
    • As CO2 levels rise, causing acidosis, hyperthermia and hypercapnia (so pH falls), oxygen is given up more readily to tissues
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27
Q

Does HbF or HbA have greater affinity for oxygen?

A
  • HbF higher affinity than HbA
    • With high affinity make more red cells to compensate to get oxygen to tissues
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28
Q

Describe the structure of normal adult haemoglobin?

A
  • 2 alpha chains
    • 4 alpha genes – 2 from mother and 2 from father
    • On chromosome 16 – only place these chains can be made
  • 2 beta chains
    • 2 beta genes
    • On chromosome 11 – downstream there are genes that can make delta chains and gamma chains
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29
Q

How many alpha genes do you have?

A
  • 4 alpha genes – 2 from mother and 2 from father
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30
Q

Where is the alpha gene located?

A

On chromosome 16 – only place these chains can be made

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31
Q

How many beta genes do you have?

A
  • 2 beta genes
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32
Q

Where is beta gene located?

A
  • On chromosome 11 – downstream there are genes that can make delta chains and gamma chains
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33
Q

What are the normal adult haemoglobin percentages of each type?

A
  • HbA (ααββ) 97%
  • HbA2 (ααδδ) 2%
  • HbF (ααγγ) 1%
    • When your born this is 97%, but during first year of life gamma genes switched off and beta genes switched on
34
Q

What chains are used to make HbA2

A
  • HbA2 (ααδδ)
35
Q

What chains are used to make HbF?

A
  • HbF (ααγγ)
36
Q

What are examples of congenital anaemias?

A
  • Membrane
    • Hereditary Spherocytosis
    • Other rarer ones
      • Hereditary elliptocytosis
      • Hereditary pyropoikilocytosis
      • South East Asian Ovalocytosis
  • Metabolic pathways (enzymes)
    • G-6-P deficiency
    • Other rarer ones
      • Pyruvate kinase deficiency
  • Haemoglobin
    • Haemoglobinopathies (inherited abnormalities of haemoglobin synthesis)
      • Thalassaemia
        • Reduced or absent globin chain production
        • Alpha, beta, delta or gamma
      • Sickle cell (HbS), or HbC, HbD, HbE….
        • Mutations leading to structurally abnormal globin chain
    • Other rarer ones
      • Hereditary sideroblastic anaemia
      • Porphyrias
37
Q

What does haemoglobinopathies mean?

A
  • Haemoglobinopathies (inherited abnormalities of haemoglobin synthesis)
38
Q

What is thalassaemia?

A
  • Reduced or absent globin chain production
  • Alpha, beta, delta or gamma
39
Q

What is sickle cell?

A
  • Sickle cell (HbS), or HbC, HbD, HbE….
    • Mutations leading to structurally abnormal globin chain
40
Q

What are some genetic disorders of the red cell membrane?

A
  • Hereditary Spherocytosis
  • Other rarer ones
    • Hereditary elliptocytosis
    • Hereditary pyropoikilocytosis
    • South East Asian Ovalocytosis
41
Q

What are some genetic disorders of the metabolic pathways in red cells?

A
  • G-6-P deficiency
  • Other rarer ones
    • Pyruvate kinase deficiency
42
Q

What are examples of haemoglobinopathies?

A
  • Thalassaemia
    • Reduced or absent globin chain production
    • Alpha, beta, delta or gamma
  • Sickle cell (HbS), or HbC, HbD, HbE….
    • Mutations leading to structurally abnormal globin chain
  • Other rarer ones
    • Hereditary sideroblastic anaemia
    • Porphyrias
43
Q

What kind of inheritance do most congenital anaemias display?

A

Autosomal recessive

44
Q

Describes the genetics of hereditary spherocytosis?

A
  • Most common forms autosomal dominant
45
Q

Describe the pathophysiology of hereditary spherocytosis?

A
  • Defects in 5 different structural proteins
    • Ankyrin
    • Alpha spectrin
    • Beta spectrin
    • Band 3
    • Protein 4.2
  • Causing red cells to be spherical
  • Removed from circulation by the RE system (extra-vascular)
46
Q

Describe the presentation of hereditary spherocytosis?

A
  • Variable, depending on which proteins affected
  • Anaemia
  • Jaundice (neonatal in severe types)
  • Splenomegaly
    • Due to working extra eliminating these cells
  • Pigment gallstones
    • Due to increased bilirubin crystallising in gallbladder
47
Q

Describe the treatment for hereditary spherocytosis?

A
  • Folic acid
    • If mild
  • Transfusion
    • If severe
  • Splenectomy
    • If very severe
48
Q

Describe the genetics of glucose-6-phosphate dehydrogenase deficiency?

A
  • X linked
    • Affects males
    • Female carriers
49
Q

Describe the pathophysiology of G-6-P dehydrogenase deficiency?

A
  • Cells vulnerable to oxidative damage
  • Causing haemolysis in circulation, creation of blister cells
50
Q

What is the commonest disease causing enzymopathy?

A

G-6-P dehydrogenase deficiency

51
Q

Describe the presentation of G-6-P dehydrogenase deficiency?

A
  • Variable degrees of anaemia
  • Neonatal jaundice
  • Splenomegaly
  • Pigment gallstones
52
Q

Presentation of G-6-P dehydrogenase deficiency is precipitated by?

A
  • Drugs, broad bean, acute illness or infection
    • Causes intravascular haemolysis
    • Haemoglobinuria – due to bursting red cells in circulation
53
Q

Describe the pathophysiology of pyruvate kinase deficiency?

A
  • Reduced ATP
  • Increased 2, 3-DPG
  • Cells rigid
54
Q

Describe the presentation of pyruvate kinase deficiency?

A
  • Anaemia
  • Jaundice
  • Gallstones
55
Q

Where are haemoglobinopathies most common?

A
  • More common in areas where malaria is or was prevalent
56
Q

Describe the genetics of haemoglobinopathies?

A
  • Autosomal recessive inheritance
    • 1/4 chance of having affected carrier
    • 1/2 chance of being a carrier
57
Q

Being a carrier of haemoglobinopathies confers what?

A

Being a carrier confers resistance to severe malaria infection

58
Q

Describe the pathophysiology of sickle cell disease?

A
  • Sickle cell haemoglobin (HbS) composed of haem molecule and 2 alpha chains and 2 beta (sickle chains)
    • Point mutation
  • Red cell changes shape to rigid sickle cells
    • Can damage red cell membrane, leakage of cells and they become dehydrated
    • Haemolysis then causes endothelial activation, promotion of inflammation, coagulation activation, dysregulation of vasomotor tone by vasodilator mediators (NO)
    • Vaso-occlusion
59
Q

Descibe the presentation of sickle cell disease?

A
  • Multi-system disorder
  • Painful vaso-occlusive crises
    • Bone pain
  • Chest crises
  • Stroke
  • Increased infection risk
    • Hyposplenism
  • Chronic haemolytic anaemia
    • Gallstones
    • Aplastic crises
  • Sequestration crises (pooling of blood)
    • Spleen
    • Liver
60
Q

Describe the treatment of a painful sickle cell disease crises?

A
  • Pain management
    • Opiates
  • Hydration
  • Oxygen
  • Consider antibiotics
61
Q

Describe the management of sickle cell disease?

A
  • Vaccination
    • Against organisms that can cause infection
  • Penicillin prophylaxis
  • Folic acid
62
Q

Describe the mangement of acute events due to sickle cell disease?

A
  • Hydration
  • Oxygenation
  • Prompt treatment of infection
  • Analgesia
    • Opiates
    • NSAIDs
  • Blood transfusion
    • Episodic or chronic
      • Complications – alloimmunisation, iron overload
  • Disease modifying drugs
    • Hydroxycarbamide
    • Bone marrow transplantation
    • Gene therapy
63
Q

What analgesics should be used for sickle cell during acute events?

A
  • Opiates
  • NSAIDs
64
Q

What are some disease modifying drugs for sickle cell disease?

A
  • Hydroxycarbamide
  • Bone marrow transplantation
  • Gene therapy
65
Q

What is thalassaemia?

A

Reduced or absent globin chain deletions:

  • Can lose all genes, or just one
66
Q

What are the different kinds of thalassaemias?

A
  • Alpha thalassaemia
  • Beta thalassaemia
67
Q

Describe the pathophysiology of thalassaemia?

A
  • Chain imbalance (free chains floating about – if reduction in beta chains then alpha chains floating around)
  • Causing chronic haemolysis and anaemia
68
Q

What is “a” thalassaemia?

A
69
Q

What is “a0” thalassaemia?

A
70
Q

What is homozygous alpha zero thalassaemia?

A
  • Homozygous alpha zero thalassaemia (a0/a0)
    • No alpha chains
    • Hydrops fetalis – incompatible with life
71
Q

What is beta thalassaemia major?

A
  • Beta thalassaemia major (homozygous beta thalassaemia)
    • No beta chains
    • Transfusion dependent anaemia (severe anaemia)
72
Q

Describe the presentation of beta thalassaemia major?

A
  • Presentation – at 3-6 months age, expansion of ineffective bone marrow, bony deformities (due to bone marrow trying to make more red cells), splenomegaly, growth retardation
73
Q

Describe the prognosis of beta thalassaemia major?

A
  • Prognosis – if untreated or with irregular transfusions is <10 years
74
Q

Describe the treatment for beta thalassaemia major?

A
  • Treatment – chronic transfusion support 4-6 weekly, iron chelation therapy (s/c desforrioxamine infusions or oral deferasirox), regular monitoring of ferritin and MRI scans, possible bone marrow transplantation
    • Side effect – iron overload
75
Q

What is thalassaemia minor?

A
  • Thalassaemia minor (common)
    • “Trait” or carrier state, only lost one gene
    • Hypochronic microcytic red cell indices (small red cells)
76
Q

Describe the spectrum of severity for thalassaemia?

A
  • Homozygous alpha zero thalassaemia (a0/a0)
    • No alpha chains
    • Hydrops fetalis – incompatible with life
  • Beta thalassaemia major (homozygous beta thalassaemia)
    • No beta chains
    • Transfusion dependent anaemia (severe anaemia)
    • Presentation – at 3-6 months age, expansion of ineffective bone marrow, bony deformities (due to bone marrow trying to make more red cells), splenomegaly, growth retardation
    • Prognosis – if untreated or with irregular transfusions is <10 years
    • Treatment – chronic transfusion support 4-6 weekly, iron chelation therapy (s/c desforrioxamine infusions or oral deferasirox), regular monitoring of ferritin and MRI scans, possible bone marrow transplantation
      • Side effect – iron overload
  • Non-transfusion dependent thalassaemia
    • Range of genotypes
  • Thalassaemia minor (common)
    • “Trait” or carrier state, only lost one gene
    • Hypochronic microcytic red cell indices (small red cells)
77
Q

What is sideroblastic anaemia?

A

Sideroblastic anemia is a group of blood disorders characterized by an impaired ability of the bone marrow to produce normal red blood cells . In this condition, the iron inside red blood cells is inadequately used to make hemoglobin, despite normal amounts of iron.

78
Q

Describe the aetiology of sideroblastic anaemia?

A
  • ALA synthase mutations
  • Hereditary
  • Acquired
79
Q

Describe the pathophysiology of sideroblastric anaemia?

A
  • Defects in mitochondrial steps of haem synthesis
80
Q

Describe the pathophysiology of porphyrias?

A
  • Defects in cytoplasmic steps of haem synthesis

Immunology and Haematology (23 decks)

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