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MCD Y2: Haematology > Hb and Thalassaemia > Flashcards

Hb and Thalassaemia Flashcards

1
Q

What is on the x and y axis of the Hb dissociation curve?

A 
x = ppO2
y = HbO2(%)
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2
Q

How does a left/ right shift of the O2 dissociation curve describe a change in affinity for oxygen?

A 
Left = higher affinity
Right = lower affinity
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3
Q

Recall 5 factors that affect the position of the O2 dissociation curve

A 
[2,3-DPG]
pH
[CO2]
%HbS
%HbF
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4
Q

Which direction does the O2 dissociation curve move in when the concentration of 2,3-DPG increases?

A

right

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5
Q

Describe the effect of HbS/ HbF on the position of the oxygen dissociation curve

A

HbS increase –> right

HbF increase –> left

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6
Q

What is the normal concentration of Hb in adults?

A

120-165g/L

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7
Q

What mass of iron is contained within one gram of Hb?

A

3.4mg

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8
Q

Recall the structure of haem

A

Protoporphyrin ring + central iron (usually ferrous)

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9
Q

Where is haem synthesised and what enzyme is used?

A

Mitochondria - ALAS

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10
Q

How many amino acids are in an alpha globin chain?

A

141

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11
Q

How many amino acids are in a non-alpha globin chain?

A

146

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12
Q

Recall the location and arrangement of the globin genes

A

Arrangement: 2 clusters - alpha = 2 x alpha and an epsilon gene, beta = beta, gamma and delta globin genes
Location: alpha = c16, beta = c11

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13
Q

What globin chains make up foetal Hb?

A

alpha and gamma

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14
Q

What is the normal adult concentration of erythrocytes?

A

3.5-5x10^12/ L

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15
Q

When is Hb synthesised?

A

During development of erythrocyte: begins in pro-erythroblast stage and completed in reticulocyte stage

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16
Q

Where are globin chains synthesised?

A

ribosomes

17
Q

Which globin chains make up HbA2?

A

2 alpha and 2 delta

18
Q

Recall the aetiology of beta thalassaemia

A

Defective/ absent beta globin chains

19
Q

Recall the inheritance of beta thalassaemia

A

recessive

20
Q

What is required to cause beta thalassaemia major?

A

2 copies of thalassaemia gene

21
Q

Which 3 tests can be done in the laboratory for beta thalassaemia

A

FBC
Blood film
HPLC

22
Q

Recall 2 findings in an FBC of someone with beta thalassaemia

A
  1. Microcytic hypochromic indices

2. Increased RBC: Hb ratio

23
Q

Recall 3 features of a blood film in beta thalassaemia

A

Target cells
Poikilocytosis
NO anisocytosis

24
Q

How do beta and alpha thalassaemia differ when subjected to HPLC

A 
Beta = raised hbA2 and HbF
Alpha = fairly inconspicuous
25
Q

What causes severe alpha thalassaemia?

A

Defect in 3 out of 4 alpha genes (4 is fatal in utero)

26
Q

What is the MAIN clinical presentation of thalassaemia?

A

severe anaemia

27
Q

What is the cause of hepatosplenomegaly in thalassaemia?

A

extramedullary haematopoiesis

28
Q

Describe the blood film in SEVERE thalassaemia

A

Gross hypochromia
Poikiliocytosis
Many nucleated erythrocytes

29
Q

How are iron levels affected by thalassaemia major?

A

Iron OVERLOAD

30
Q

Recall 3 possible effects of iron overload

A

Cholelithiasis
Cardiac failure
Endocrinopathies

31
Q

What are the first-line treatments for thalassaemia?

A

Blood transfusions

Iron chelation

32
Q

When should iron chelation be started?

A

When serum ferritin is >1000mcg/L

As early as poss to avoid iron overload

33
Q

Recall the 3 available drugs for iron chelation

A

Desferrioxamine
Deferprone
Deferasirox

34
Q

Compare the administration methods of each available iron chelator drug

A

Desferrioxamine is parenteral but deferiprone and defasirox are administered orally

35
Q

Compare the toxicity of each available iron chelator drug

A

Deferrioxamine: toxic to eyes, ears and bones
Deferiprone: causes agranulocytosis, arthropathy and Zn deficiency
Deferasirox has limited toxicity

MCD Y2: Haematology (11 decks)

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