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Haematology > Congenital Anaemias > Flashcards

Congenital Anaemias Flashcards

1
Q

Define anaemia

A

Reduction in red cells/their Hb content

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2
Q

What can cause anaemia?

A

Blood loss
Decreased production
Increased destruction
Abnormal production

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3
Q

Where are red cells produced?

A

Bone marrow

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4
Q

What are the main substances required for the production of red cells?

A

Iron, B12, folate and erythropoietin

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5
Q

What is a reticulocyte?

A

A red blood that has just reached the circulation (still has a little bit of RNA in it)

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6
Q

How long do red blood cells live for?

A

120 days

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7
Q

Where is erythropoietin produced? What is its function?

A

Produced in kidneys

Function: stimulate red cell production

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8
Q

How are red cells broken down?

A

By reticuloendothelial system (i.e. macrophages in spleen and liver)

Globin broken down into amino acids, which can be built back into globin

Haem: iron reused, haem converted to biliverdin –> bilirubin

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9
Q

How can you divide up congenital anaemias?

A

Problems with:
Membrane
Enzymes
Haemoglobin

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10
Q

What are the characteristics of erythrocytes?

A

Deformable to allow them to move through vasculature
Biconcave disc
No nucleus

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11
Q

What do most congenital anaemias result in?

A

Haemolysis (as abnormal cells are produced which get broken down quicker in the blood)

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12
Q

What are the main proteins in the cell membrane of the red cells?

A

Ankyrin
Spectrin alpha and spectrin beta
Band 3

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13
Q

What are the function of proteins in the cell membrane of the red cells?

A

Maintaining red cell shape and deformability

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14
Q

What is hereditary spherocytosis?

A

Defects in proteins of red cell membrane lead to abnormally spherical shaped red cell which is removed from the circulation by the RES (in spleen)

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15
Q

What is the clinical presentation of hereditary spherocytosis?

A

Variable
Anaemia (increased red cell breakdown)
Neonatal jaundice (bilirubin rises, neonatal RES less able to cope)
Splenomegaly
Pigmented gallstones (precipitating of bilirubin)

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16
Q

How do you treat hereditary spherocytosis?

A

Folic acid
Transfusion (tends to be in acute situations, e.g. if someone unwell –> increased haemolysis)
Splenectomy (as spleen main site of red cell destruction)

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17
Q

What is the name of the system that protects red cells from oxidative damage?

A

Pentose phosphate shunt

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18
Q

What is the role of G6PD in protecting the cell from oxidative damage?

A

Increases level of reduced glutathione which breaks down free radicals into water

(only source of NAPDH which is vital for reduction of glutathione)

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19
Q

What occurs in G6PD deficiency?

A

Free radical’s damage the cell membrane leading to intravascular haemolysis

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20
Q

What is the appearance of the cells in G6PD deficiency?

A

Blister and bite cells (burst cells)

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21
Q

What kind of inheritance is G6PD deficiency?

A

X linked

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22
Q

What does G6PD deficiency confer a selective survival advantage against?

A

Malaria

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23
Q

What is the clinical presentation of G6PD deficiency?

A

Neonatal jaundice
Splenomegaly
Pigmented gallstones
TRIGGER that tends to cause symptoms

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24
Q

Intravascular haemolysis in G6PD deficiency can lead to what?

A

Haemoglobinuria which means haemoglobin leaks through the kidneys

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25
Q

What can trigger symptoms in G6PD deficiency?

A 
Infection
Acute illness, e.g. DKA
Broad beans
Antimalarials
Antibacterials
Aspirin (at high doses) 
Others
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26
Q

What does pyruvate kinase deficiency lead to?

A

Reduced ATP –> increased 2, 3-DPG –> cells become rigid and more liable to be haemolysed in the circulation

27
Q

What is the presentation of pyruvate kinase?

A

Anaemia
Gallstones
Jaundice

28
Q

What is the structure of haemoglobin?

A

4 globin chains
Haem

Relaxed when carrying oxygen 2, 3-DPG makes it tighter when giving away oxygen

29
Q

What factors shift the Hb-Oxygen binding chart to the right (i.e. make Hb more likely to let go of its oxygen)?

A 
Acidosis
Hyperthermia
Increased DPG 
Increased CO2
I.e. when you need oxygen
30
Q

What is the function of haemoglobin?

A

Carry carbon dioxide to the lungs and oxygen to the tissues

31
Q

How many genes code for alpha globin chains?

A

4 (2 x each parent)

32
Q

How many genes code for beta globin chains?

A

2 (1 x each parent)

33
Q

Which chromosome is the alpha gene on?

A

16

34
Q

Which chromosome is the beta gene on?

A

11

35
Q

What is HbA composed of and what % of blood does it make up?

A

2 alpha and 2 beta

97%

36
Q

What is HbA2 composed of and what % of blood does it make up?

A

2 alpha and 2 delta

2%

37
Q

What is HbF composed of and what % of blood does it make up?

A

2 alpha and 2 gamma

1%

38
Q

If you have no functioning alpha genes how will you present?

A

No alpha genes incompatible with life

39
Q

If you have no functioning beta genes what will happen?

A

Delta and gamma genes will compensate

40
Q

Define thalassaemia

A

Reduced/absent globin chain production

41
Q

What is the most common thalassaemia?

A

Sickle cell disease

42
Q

What type of inheritance is sickle cell disease?

A

Autosomal recessive

43
Q

What is the Hb like in sickle cell disease?

A

2 normal alpha chains
2 beta sickle chains (GLUTAMINE replaced by VALINE) –>
HbS

44
Q

What is the problem with HbS?

A

HbS doesn’t respond well to hypoxia and crystallises (all the HbS’s stick together) and this forms a sickle shaped cell (this is irreversible)

45
Q

What happens to the sickle cells in the vasculature?

A

Abnormal cells have a weak cell membrane and undergo intravascular haemolysis –> endothelial activation, promotion of inflammation, cogulation activation, dysregulation of vasomotor tone by vasodilator mediators (NO) –> vaso-occulsions

46
Q

What is the clinical presentation of sickle cell disease?

A

PAIN - requiring opiates (due to vaso-occlusive crises, esp in bone)
Strokes
Chest crisis
Increased infection risk (infarcts of spleen/spleen atrophy –> increased infection)
Chronic haemolytic anaemia (gallstones, ,aplastic crisis)
Sequestration crises

47
Q

What is an aplastic crisis?

A

When reticulocyte is reduced, e.g. during infection with Parovirus

In individuals with sickle cell disease, they rely on a high turn over of blood cells and can become very ill when not enough reticulocytes are being produced & present with acute severe anaemia

48
Q

What are sequestration crises?

A

Blood pools due to occlusion of vessels

Occurs in liver and spleen

49
Q

How do you manage a painful crisis of sickle cell disease?

A

Opiates (within 30m)
Hydration
Oxygenation
Consider antibiotics

Don’t transfuse
Find trigger

50
Q

What occurs in sickle cell chest crisis?

A

Sickling in lung leads to hypoxia –> more sickling –> more hypoxia and so on

Can be lifethreatening

51
Q

What are the symptoms/signs of sickle cell chest crisis?

A

Chest pain
Fever
Worsening hypoxia
Infiltrates on XRay

52
Q

How do you treat sickle cell chest crisis?

A 
Respiratory support
Antibiotics
IV fluids
Analgesia
Transfusion - get HbS <30%
53
Q

What is involved in long term prophylaxis of sickle cell disease?

A

Vaccination
Penicillin and malarial prophylaxis
Folic acid

54
Q

How do you treat acute events in sickle cell disease?

A 
Hydration 
Oxygenation 
Prompt treatment of infection 
Analgesia (opiates, NSAIDs) 
?Blood transfusion
55
Q

What is the only disease modifying drug for sickle cell disease?

A

Hydroxycarbamide - increases Hb

56
Q

What are last resort treatments for sickle cell disease?

A

Bone marrow transplantation and gene therapy - for high risk patients only

57
Q

What is the name of the condition that results from homozygous alpha zero thalassaemia?

A

Hydrops fetalis

58
Q

What is beta thalassaemia major?

A

Homozygous beta thalassaemia
No beta chains
Transfusion dependent

59
Q

What are the non-transfusion dependent thalassaemias?

A

Smaller mutations of beta gene

may still require transfusions at time of stress

60
Q

What is thalassaemia minor?

A

Trait/carrier state

May get hypochromic microcytic red cells (small red cells, mild anaemia)

61
Q

What is the clinical presentation of beta thalassaemia minor?

A 
Severe anaemia (present at 3-6 months) 
Expansion of ineffective bone marrow 
Bony deformities 
Splenomegaly (as spleen tries to make red cells and take over) 
Growth retardation
62
Q

If beta thalassaemia isn’t treated what will occur?

A

Death

63
Q

How do you treat beta thalassaemia major?

A

Chronic transfusion support every 4-6 weeks

BEWARE of iron overloading - so also require iron chelation therapy (s/c desferrioxamine until able to take oral deferasirox)

Bone marrow transplantation curative

64
Q

What are sideroblastic anaemias?

A

Defects in mitochondrial steps of haem synthesis

Haematology (14 decks)

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