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Immunology and Haematology Brian > 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
What molecule holds deoxyhaemoglobin in tight structure?
2-3 - DPG
26
Describe the oxygen dissociation curve?
* 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
27
Does HbF or HbA have greater affinity for oxygen?
* HbF higher affinity than HbA * With high affinity make more red cells to compensate to get oxygen to tissues
28
Describe the structure of normal adult haemoglobin?
* 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
29
How many alpha genes do you have?
* 4 alpha genes – 2 from mother and 2 from father
30
Where is the alpha gene located?
On chromosome 16 – only place these chains can be made
31
How many beta genes do you have?
* 2 beta genes
32
Where is beta gene located?
* On chromosome 11 – downstream there are genes that can make delta chains and gamma chains
33
What are the normal adult haemoglobin percentages of each type?
* 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
What chains are used to make HbA2
* HbA2 (ααδδ)
35
What chains are used to make HbF?
* HbF (ααγγ)
36
What are examples of congenital anaemias?
* 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
What does haemoglobinopathies mean?
* Haemoglobinopathies (inherited abnormalities of haemoglobin synthesis)
38
What is thalassaemia?
* Reduced or absent globin chain production * Alpha, beta, delta or gamma
39
What is sickle cell?
* Sickle cell (HbS), or HbC, HbD, HbE…. * Mutations leading to structurally abnormal globin chain
40
What are some genetic disorders of the red cell membrane?
* Hereditary Spherocytosis * Other rarer ones * Hereditary elliptocytosis * Hereditary pyropoikilocytosis * South East Asian Ovalocytosis
41
What are some genetic disorders of the metabolic pathways in red cells?
* G-6-P deficiency * Other rarer ones * Pyruvate kinase deficiency
42
What are examples of haemoglobinopathies?
* **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
What kind of inheritance do most congenital anaemias display?
Autosomal recessive
44
Describes the genetics of hereditary spherocytosis?
* Most common forms autosomal dominant
45
Describe the pathophysiology of hereditary spherocytosis?
* 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
Describe the presentation of hereditary spherocytosis?
* 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
Describe the treatment for hereditary spherocytosis?
* Folic acid * If mild * Transfusion * If severe * Splenectomy * If very severe
48
Describe the genetics of glucose-6-phosphate dehydrogenase deficiency?
* X linked * Affects males * Female carriers
49
Describe the pathophysiology of G-6-P dehydrogenase deficiency?
* Cells vulnerable to oxidative damage * Causing haemolysis in circulation, creation of blister cells
50
What is the commonest disease causing enzymopathy?
G-6-P dehydrogenase deficiency
51
Describe the presentation of G-6-P dehydrogenase deficiency?
* Variable degrees of anaemia * Neonatal jaundice * Splenomegaly * Pigment gallstones
52
Presentation of G-6-P dehydrogenase deficiency is precipitated by?
* Drugs, broad bean, acute illness or infection * Causes intravascular haemolysis * Haemoglobinuria – due to bursting red cells in circulation
53
Describe the pathophysiology of pyruvate kinase deficiency?
* Reduced ATP * Increased 2, 3-DPG * Cells rigid
54
Describe the presentation of pyruvate kinase deficiency?
* Anaemia * Jaundice * Gallstones
55
Where are haemoglobinopathies most common?
* More common in areas where malaria is or was prevalent
56
Describe the genetics of haemoglobinopathies?
* Autosomal recessive inheritance * 1/4 chance of having affected carrier * 1/2 chance of being a carrier
57
Being a carrier of haemoglobinopathies confers what?
Being a carrier confers resistance to severe malaria infection
58
Describe the pathophysiology of sickle cell disease?
* 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
Descibe the presentation of sickle cell disease?
* 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
Describe the treatment of a painful sickle cell disease crises?
* Pain management * Opiates * Hydration * Oxygen * Consider antibiotics
61
Describe the management of sickle cell disease?
* Vaccination * Against organisms that can cause infection * Penicillin prophylaxis * Folic acid
62
Describe the mangement of acute events due to sickle cell disease?
* 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
What analgesics should be used for sickle cell during acute events?
* Opiates * NSAIDs
64
What are some disease modifying drugs for sickle cell disease?
* Hydroxycarbamide * Bone marrow transplantation * Gene therapy
65
What is thalassaemia?
Reduced or absent globin chain deletions: * Can lose all genes, or just one
66
What are the different kinds of thalassaemias?
* Alpha thalassaemia * Beta thalassaemia
67
Describe the pathophysiology of thalassaemia?
* Chain imbalance (free chains floating about – if reduction in beta chains then alpha chains floating around) * Causing chronic haemolysis and anaemia
68
What is "a" thalassaemia?
69
What is "a0" thalassaemia?
70
What is homozygous alpha zero thalassaemia?
* Homozygous alpha zero thalassaemia (a0/a0) * No alpha chains * Hydrops fetalis – incompatible with life
71
What is beta thalassaemia major?
* Beta thalassaemia major (homozygous beta thalassaemia) * No beta chains * Transfusion dependent anaemia (severe anaemia)
72
Describe the presentation of beta thalassaemia major?
* 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
Describe the prognosis of beta thalassaemia major?
* Prognosis – if untreated or with irregular transfusions is \<10 years
74
Describe the treatment for beta thalassaemia major?
* 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
What is thalassaemia minor?
* Thalassaemia minor (common) * “Trait” or carrier state, only lost one gene * Hypochronic microcytic red cell indices (small red cells)
76
Describe the spectrum of severity for thalassaemia?
* **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
What is sideroblastic anaemia?
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
Describe the aetiology of sideroblastic anaemia?
* ALA synthase mutations * Hereditary * Acquired
79
Describe the pathophysiology of sideroblastric anaemia?
* Defects in mitochondrial steps of haem synthesis
80
Describe the pathophysiology of porphyrias?
* Defects in cytoplasmic steps of haem synthesis

Immunology and Haematology Brian (23 decks)

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