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2=Haematology > 3. Haemoglobinopathies and Thalassaemia > Flashcards

3. Haemoglobinopathies and Thalassaemia Flashcards

1
Q

how many types of Hb are found in human blood?

A

3

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2
Q

what are the 3 types of Hb found in human blood?

A

HbA
HbA(2)
HbF (foetal)

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3
Q

on which Ch is the alpha globin gene?

A

16

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4
Q

on which Ch is the beta, gamma, delta globin gene?

A

11

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5
Q

how many copies of the alpha gene do we have?

A

2 on each chromosome - 4 in total

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6
Q

how many copies of the beta, gamma, delta globin gene do we have?

A

2 of each

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7
Q

after 3-6 of birth, what does HbF change into?

A

HbA

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8
Q

what occurs in terms of genes in the transfer of HbF into HbA?

A

gamma is replaced by beta

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9
Q

what is a haemoglobinopathy?

A

a mutation in the globin genes which give rise to different types and amounts of Hb

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10
Q

2 types of haemoglobinopathy

A

thalassaemia and structural variant

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11
Q

what does the mutation in thalassaemia result in?

A

functional but reduced/no synthesis of globin genes

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12
Q

what does the mutation in the structural variant result in?

A

non-functional globin genes

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13
Q

is the defect in thalassaemia quantitative or qualitative?

A

quantitative

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14
Q

is the defect in structural variant quantitative or qualitative?

A

qualitative

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15
Q

name the 4 most common structural variants of Hb?

A

SCED

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16
Q

what type of mutation occurs in SVHb?

A

point mutation within globin genes - usually AA substitution

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17
Q

which SVHb is most prevalent in punjab?

A

HbD

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18
Q

which SVHb is most prevalent in south east asia?

A

HbE

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19
Q

which SVHb is most prevalent in west + central africa?

A

HbC

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20
Q

which 4 places is HbS most prevalent?

A
  1. tropical africa
  2. afro-caribbean
  3. south mediterranean
  4. central india
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21
Q

which disease is caused by HbS?

A

sickle cell disease

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22
Q

what is glutamic acid replaced with in HbC, and at what position?

A

lysine - position 6

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23
Q

what is glutamic acid replaced with in HbE, and at what position?

A

lysine - position 26

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24
Q

what is glutamic acid replaced with in HbD, and at what position?

A

glutamine - position121

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25
Q

which 2 SVHb cause mild haemolytic anaemia?

A

D and C

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26
Q

which SVHb results in an enlarged spleen?

A

HbC

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27
Q

what type of anaemia is caused by HbE?

A

mild microcytic hypochromic

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28
Q

what disease does the Hb trait protect against?

A

malaria

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29
Q

which is the most frequent SVHb?

A

HbS

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30
Q

where does the mutation occur in Sickle cell disease - at what point - what occurs?

A

in one or both of the beta genes. glutamic acid is replaced by valine in position 6.

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31
Q

what causes the change in shape to sickle in HbS?

A

HbS is less soluble when deoxygenated compared to HbA

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32
Q

3 predispositioning factors of SCD?

A
  1. hypoxia
  2. acidosis
  3. increased body temperature
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33
Q

when can sickling be reversed?

A

after reoxygenation

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34
Q

when is sickling irreverssible?

A

after repeated cycles of oxygenation and deoxygenation

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35
Q

describe genes in heterozygous SCD. how many beta genes are affected?

A

Hb A + Hb S - only 1 affected

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36
Q

describe Hb and RBC levels in heterozyous SCD

A

normal

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37
Q

describe 3 sxs in heterozyous SCD

A
  1. asymptomatic
  2. haematuria
  3. renal papillary necrosis
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38
Q

in what 3 conditions must patients with heterozyous SCD be carefully observed?

A
  1. high altitude
  2. pregnancy
  3. anaetheesia

<40% oxygen

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39
Q

what type of anaemia is caused by homozygous SCD?

A

severe haemolytic

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40
Q

the clinical expression of homozygous SCD is variable and can lead to one of three outcomes; which are

A
  1. shortened lifespan
  2. normal life
  3. severe crises
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41
Q

name 5 clinical features of homozygous SCD

A
  1. priapism
  2. kidney infections
  3. pulmonary hypertension
  4. susceptability to infections
  5. retinopathy
  6. ulcers of lower leg
  7. dactylitis
  8. enlarged spleen
  9. liver damage
  10. gallstones
  11. severe crises
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42
Q

why do gallstones form in homozygous SCD?

A

haemolysis causes breakdown of RBC and build up of bilirubin

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43
Q

name 4 types of crises

A
  1. haemolytic
  2. vaso-occlusive
  3. visceral sequestration
  4. aplastic
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44
Q

what 3 things precipitate vaso-occlusive crises?

A
  1. deoxygenation
  2. dehydration
  3. infection
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45
Q

which 4 places do vaso-occlusive crises occur?

A

brain, spleen, lungs, bones

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46
Q

what is visercal sequestration crises caused by?

A

accumulation of sickle cells in an organ

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47
Q

what syndrome does visercal sequestration crises lead to?

A

sickle chest syndrome

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48
Q

3 types of visercal sequestration crises

A

splenic, hepatic, girdle

49
Q

which type of visercal sequestration crises occurs in infants?

A

splenic

50
Q

2 causes of aplastic crises?

A

parvo virus

folic acid deficiency

51
Q

characteristics of aplastic crises?

A

sudden drop in Hb

fall in reticulocytes

52
Q

how to differentiate aplastic and haemolytic crises?

A

aplastic - fall in reticulocytes

haemolytic - rise

53
Q

characteristics of haemolytic crises

A
  1. fall in HB
  2. rise in reticulocytes
  3. pain
54
Q

lab findings of SCD

A
  1. low Hb 60-90g/l
  2. howell-jolly bodies
  3. screening shows sickle +ve
  4. Hb electrophoresis shows prescence of HbS (no HbA)
  5. raised HbF
55
Q

what are howell-jolly bodies?

A

remnants of DNA

56
Q

which test differentiates between homozgous and heterozygous SCD; i) sickle solubility test ii) Hb electrophoresis iii) both

A

ii) Hb electrophoresis

57
Q

what would show SCD in the sickle solubility test?

A

cloudy tube - shows HbS

58
Q

prophylactic treatment of SCD

A
  1. vaccination
  2. folic acid
  3. AB to reduce infection risk
59
Q

why is folic acid given as a prophylactic treatment of SCD?

A

increase DNA and Hb production

60
Q

treatment after crises of SCD

A
  1. rest
  2. rehydration
  3. warmth
  4. pain relief
61
Q

what is the only cure to SCD?

A

transplantation

62
Q

why is transfusion given in SCD?

A

RBC low

63
Q

why is hydroxyurea given in SCD?

A

raise HbF

64
Q

which 2 things have reduced the mortality rate of SCD

A
  1. vaccination

2. awareness of acute splenic sequestratation syndrome to parents

65
Q

what clinical features would arise from a combination o HbS and HbC genes?

A

same as homozygous HbS

66
Q

what clinical features would arise from a combination o HbS and beta genes?

A

thalasseamia

67
Q

2 causes of thalassaemia (T)

A
  1. ineffective erythropoiesis

2. shortened RBC lifespan

68
Q

what are the 3 classification criteria of T?

A
  1. affected globin gene - alpha or beta
  2. reduction in rate of synthesis of globin - total or partial
  3. genotype - heterozygos or homozygous
69
Q

where is T common?

A

malaria endemic areas

70
Q

which continent is alpha T most common?

A

east asia

71
Q

where is beta T most prevalent?

A
  1. mediterraen
  2. africa
  3. greece
  4. india
72
Q

what type of mutation causes 95% of a-thalassaemias?

A

deletion - in 1 or both pairs of genes

73
Q

what type of mutation causes 5% of a-thalassaemias?

A

point mutations

74
Q

name 6 possible genotypes of alpha T mutation

A
  1. normal
  2. a+ heterozygote
  3. a+ homozygote
  4. a0 heterozygote
  5. a0 homozygote
  6. a+ a0 double heterozygote
75
Q

genetic makeup of a+ heterozygote

A

a-/aa

76
Q

what is the main ruling for a+

A

only affecting one of the chromosome on one gene

77
Q

genetic makeup of a+ homozygote

A

a-/a-

78
Q

genetic makeup of a0 heterozygote

A

–/aa

79
Q

what is the main ruling for a0

A

affects both chromosomes on both genes

80
Q

genetic makeup of a0 homozygote

A

–/–

81
Q

a+ a0 double heterozygote

A

–/a-

82
Q

which a-T genotype is incompatible with life?

A

–/– a0 homozygote

83
Q

which a-T genotype is a silent carrier?

A

a+ heterozygote a-/aa

84
Q

which 2 a-T genotypes code for the A thalassaemia trait?

A

a+ homo a-/a-

a0 hetero –/aa

85
Q

which a-T genotype codes for the Barts hydrops foetalis disease ?

A

a0 homozygote –/–

86
Q

what disease does the a0a+double heterozygote code for?

A

Hb H disease

87
Q

which process will differentiate between a+ and a0 for alpha-T?

i) gel electrophoresis
ii) DNA analysis
iii) both

A

DNA analysis

88
Q

which type of anaemia does alpha-T cause?

A

mild microcytic hypochromic

89
Q

how to differentiate between a+ and a0 a-T?

A

mean cell Hb is lower in a0 than a+

90
Q

which type and severity of anaemia does Hb H disease cause?

A

moderate-severe microcytic, hypochromasia anaemia

91
Q

other clinical features of Hb H disease

A

hepatosplenomegaly

92
Q

what does hypochromasia mean?

A

increase in central pallor of RBC

93
Q

what does polychromasia mean?

A

high number of immature RBC

94
Q

why is Hb H disease a problem?

A

it produces Hb H which is functionally useless

95
Q

what is Hb Barts Hydrops Foetalis?

A

when only functionally usefull Hb barts and Hb H is formed - no normal is formed

96
Q

what can prevent BHF?

A

genetic counselling

97
Q

where is the mutation in b-T?

A

b globin gene

98
Q

what type of mutation in b-T?

A

point

99
Q

how are the types of b-T classified?

A

by severity of sxs

100
Q

3 types of b-T

A
  1. b-T trait
  2. b-T major
  3. b-T intermedia
101
Q

describe where the mutation is in b-T trait and b-T major

A 
trait = heterozygous = 1 beta globin gene 
major = homozygous = 2 beta globin genes
102
Q

which type of anaemia does b-T trait cause?

A

mild microcytic hypochromic

103
Q

which type of anaemia does b-T major cause?

A

severe microcytic hypochromatic anaemia

104
Q

describe the characteristics of RBC in b-T major

A

raised RBC count - nucleated RBC

105
Q

skeletal deformities in b-T major are caused by.. (2)

A
  • erythroid hyperplasia

- expansion of BM volume

106
Q

what does Hb electrophoresis show for b-T major?

A

increase in HbF and no HbA

107
Q

Name 6 other diagnostic tests for b-T major

A
  1. quantification of HbF
  2. Column chromotography
  3. Immunoassay
  4. HPLC
  5. Isoelectric focusing
  6. DNA analysis
108
Q

8 treatments for b-T major

A
  1. Regular blood transfusions
  2. Chelation therapy
  3. AB
  4. immunisation
  5. Vit C
  6. Splenectomy
  7. Folic acid
  8. BM transplant
109
Q

why are regular blood transfusions offered for b-T major?

A

to maintain Hb levels ar 100-120 g/l - to suppress erythropoieses and prevent skeletal changes

110
Q

what is a disadvantage of regular blood transfusions?

A

iron can build up - toxic

111
Q

what can solve the problem of iron build up in the body?

A

chelation therapy

112
Q

is b-T intermedia homozygous or heterozygous?

A

homozygous

113
Q

what is the difference between b-T intermedia and major?

A

less severe sxs, diseases, - does not require blood transfusions

114
Q

3 causes of BT intermedia?

A
  1. inheritance of BT mutations
  2. co-inheritance with a gene which increases the rate of gamma globin synthesis
  3. co-inheritance with a-T
115
Q

in what disease is hypersplenism prevalent?

A

bT intermedia

116
Q

if sickle cells were detected in a blood film - what furhter tests would be conducted?

A

sickledex/sickle solubility test

Hb electrophoressis

117
Q

what does a cloudly sickle test tube indicate?

A

prescence of HbS

118
Q

why does Hb electrophoresis need to be done after sickledex?

A

to find out if it is hetero or homozygous

2=Haematology (9 decks)

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