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Y3 Haematology > Haemoglobinopathies > Flashcards

Haemoglobinopathies Flashcards

1
Q

describe the structure of Hb

A

a tetramer made of two alpha globin chains and two beta globin chains, with one haem group attached to each globin

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2
Q

describe the structure of haem

A

a porphyrin ring with an iron at the centre

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3
Q

what causes the development of haemoglobinopathies?

A

problems with the globin chains

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4
Q

what is HbA?

A

adult haemoglobin

two alpha and two beta chains

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5
Q

what is HbA2?

A

2 alpha chains and 2 delta chains

a functional but rare form of Hb

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6
Q

what is HbF?

A

fetal haemoglobin

two alpha and two gamma chains

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7
Q

where are the genes for alpha globin chains found and how many are there per cell?

A

chromosome 16

two per chromosome = four per cell

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8
Q

where are the genes for beta globin chains found and how many are there per cell?

A

chromosome 11

one per chromosome = two per cell

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9
Q

when are levels of adult hemoglobin reached and what implication does this have for globin problems?

A

6-12 months of age

means problems with the beta chain wont manifest til this time, as beta globin is only found in HbA

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10
Q

what are haemoglobinopathies?

A

hereditary conditions affecting globin chain synthesis

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11
Q

what is the inheritance pattern seen in haemoglobinopathies?

A

autosomal recessive

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12
Q

what are the two main groups of haemoglobinopathies?

A

thalassaemia

structure Hb variants

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13
Q

what infection has been associated with increased rates of haemoglobinopathies in certain areas?

A

malaria

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14
Q

what are the two types of thalassaemia?

A

alpha thalassaemia

beta thalassaemia

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15
Q

what type of anaemia is seen in thalassaemia and why?

A

inadequate Hb production causes a microcytic hypochromic anaemia

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16
Q

what causes alpha thalassaemia?

A

mutations affecting alpha globin chain synthesis

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17
Q

what genotype is seen in individuals unaffected by alpha thalassaemia?

A

four normal alpha genes = (aa/aa)

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18
Q

what types of haemoglobin can be affected by alpha thalassaemia?

A

all as they all contain alpha globin (HbA, HbA2 and HbF)

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19
Q

what are the three types of alpha thalassaemia?

A

alpha thalassaemia trait
HbH disease
Hb Bart’s hydrops fetalis

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20
Q

what is the genotype of someone with alpha thalassaemia trait?

A

one or two alpha genes missing i.e. (-a/aa) or (–/aa)

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21
Q

how does alpha thalassaemia trait present?

A

asymptomatic carrier state

microcytic hypochromic red cells with normal ferritin

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22
Q

what genotype is seen in people with HbH disease?

A

only one alpha gene left (–/-a)

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23
Q

how does HbH disease present?

A

moderate to severe anaemia with very low MCV and MCH

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24
Q

what is a+ thalassaemia?

A

one alpha gene deleted from a chromosome (-a/aa)

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25
Q

what is a0 thalassamia?

A

both alpha genes deleted from a chromosome (–/aa)

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26
Q

why is HbH disease called that?

A

excess beta globin chains form tetramers

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27
Q

in which area is there a higher prevalence of HbH disease?

A

south east asia

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28
Q

what is the genotype seen in Hb Bart’s?

A

no functional alpha genes (–/–)

29
Q

how does Hb Bart’s usually present?

A

intrauterine death as not compatible with life

30
Q

what causes beta thalassaemia?

A

point mutations in the beta globin chain resulting in disordered beta chain synthesis

31
Q

what type of Hb is affected by beta thalassaemia?

A

only HbA as this is the only type that contains beta chains

32
Q

what does B+ mean?

A

reduced beta chain production

33
Q

what does B0 mean?

A

absent beta chain production

34
Q

what are the three types of beta thalassaemia?

A

beta thalassaemia trait
beta thalassaemia intermedia
beta thalassaemia major

35
Q

what genotypes can be seen in beta thalassaemia trait?

A

B+/B or B0/B

36
Q

how does beta thalassaemia trait present?

A

asymptomatic
may have a mild anaemia
low MCV/MCH

37
Q

what is diagnostic of beta thalassaemia trait?

A

raised HbA2 levels

38
Q

what genotypes can be seen in beta thalassaemia intermedia?

A

B+/B+ or B0/B+

39
Q

what do patients with beta thalassaemia intermedia need?

A

occasional transfusions

40
Q

what genotype is seen in beta thalassaemia major?

A

B0/B0

41
Q

what do patients with beta thalassaemia major need?

A

lifelong transfusions

42
Q

when does beta thalassaemia major present and why?

A

6-24 months old as HbF falls

43
Q

how does beta thalassaemia major present?

A

pallor

failure to thrive

44
Q

what is the Hb target in beta thalassaemia major?

A

95-105

45
Q

what is a possible management option for beta thalassaemia major if done early?

A

bone marrow transplant

46
Q

what three systems can be impacted by iron overload?

A

endocrine
cardiac
liver

47
Q

what effects can iron overload have on the endocrine system?

A

impaired growth + development
diabetes
osteoporosis

48
Q

what effects can iron overload have on the heart?

A

cardiomyopathy

arrythmias

49
Q

what effects can iron overload have on liver disease?

A

cirrhosis

HCC

50
Q

how should iron overload be managed in an anaemic patient?

A

iron chelating drugs

51
Q

name an iron chelating drug

A

desferrioxamine

52
Q

what causes sickling disorders?

A

point mutation in codon 6 of the beta globin chain, producing Bs

alters the structure of Hb

53
Q

what type of Hb is seen in sickling disorders?

A

HbS

54
Q

what are the three types of sickling disorders?

A

sickle cell trait
sickle cell anaemia
sickle cell disease

55
Q

what haemoglobin is seen in sickle cell trait?

A

HbAS

majority is HbA

56
Q

what genotype is seen in sickle cell trait?

A

B/Bs (one normal one abnormal)

57
Q

how does sickle cell trait present?

A

asymptomatic carrier state

may sickle in severe hypoxia

58
Q

describe the appearance of the blood film in sickle cell trait

A

normal

59
Q

what haemoglobin is seen in sickle cell anaemia?

A

HbSS

60
Q

what genotype is seen in sickle cell anaemia?

A

Bs/Bs

two abnormal B genes

61
Q

how does sickle cell anaemia present?

A

episodes of sickle crisis causing severe pain

62
Q

what causes sickle crisis?

A

altered shape of RBCs resulting in vascular occlusion and tissue infarction

63
Q

what happens to the RBC lifespan in sickle cell anaemia?

A

reduced due to chronic haemolysis

64
Q

where are sickled RBCs removed in sickle cell anaemia and what effect can this have?

A

liver and spleen

hyposplenism

65
Q

name some possible precipitants of sickle crisis

A

hypoxia
dehydration
infection
stress

66
Q

how is sickle crisis managed?

A

opiate analgesia
hydration
rest
oxygen

67
Q

what needs to be given to patients with sickle cell anaemia due to hyposplenism?

A

prophylactic penicillin

regular immunisations

68
Q

what is sickle cell disease?

A

when patients have compound heterozygosity for HbS and another B chain mutation

69
Q

what investigations can be used to diagnose haemoglobinopathies?

A

HPLC

electrophoresis (less common)

Y3 Haematology (23 decks)

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