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Haematology > Haemoglobinopathies > Flashcards

Haemoglobinopathies Flashcards

1
Q

three major forms of Hb

A

HbA
HbA2
HbF

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2
Q

structure of HbA

A

2 alpha and 2 beta chains

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3
Q

structure of HbA2

A

2 alpha and 2 delta chains

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4
Q

structure of HbF

A

2 alpha and 2 gamma chains

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5
Q

which chromosome controls alpha chain production?

A

16 (2 genes per chromosome, 4 per cell)

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6
Q

which chromosome controls beta chain production?

A

chromosome 11 (1 gene per chromosome, 2 per cell)

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7
Q

define haemoglobinopathies

A

hereditary conditions affecting globin chain synthesis

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8
Q

two main groups of haemoglobinopathies

A
  1. thalassaemias

2. structural Hb variants

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9
Q

define thalassaemia’s

A

decreased rate of globin chain synthesis

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10
Q

define structural Hb variants

A

normal production of abnormal globin chains e.g. HbS

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11
Q

two types of thalassaemia’s

A
  1. alpha thalassaemia

2. beta thalassaemia

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12
Q

what is alpha thalassaemia?

A

deletion of alpha genes in chromosome 16 causing reduced/ absent alpha chain synthesis (all Hb forms affected)

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13
Q

classification of alpha thalassaemia

A
  1. alpha thalassaemia trait
  2. HbH disease
  3. Hb Barts hydrops fetalis
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14
Q

define alpha thalassaemia trait

A

one or two alpha genes are missing
asymptomatic carrier state
mild anaemia 105-110

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15
Q

difference between thalassaemia and iron deficiency anaemia?

A

ferritin is normal in thalassaemia trait

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16
Q

define HbH disease?

A

only one alpha gene left so the excess beta chains form tetramers (beta4) called HbH

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17
Q

blood results of HbH disease

A

anaemia 50-90
low MCV
low MCH

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18
Q

diagnosis of HbH disease

A

red cell inclusions of HbH seen on staining

FBC

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19
Q

presentation of HbH disease

A

jaundice
splenomegaly
anaemia

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20
Q

where is HbH disease common

A

SE Asia

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21
Q

management of HbH disease

A

transfusion

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22
Q

define Hb Barts hydrops fetalis

A

no functional alpha genes so no HbF or HbA causing tetramers of Hb Barts (gamma4) and HbH (beta4)

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23
Q

presentation of Hb Barts hydrops fetalis

A 
profound anaemia
cardiac failure
growth retardation
severe hepatosplenomegaly
skeletal abnormalities
most die in-utero
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24
Q

diagnosis of Hb Barts hydrops fetalis

A

antenatal screening

risk increased if both parents from SE Asia

25
Q

common cause of beta thalassaemia

A

point mutations

26
Q

which Hb is affected in beta thalassaemia?

A

only HbA

27
Q

classification of beta thalassaemia

A
  1. beta thalassaemia trait
  2. beta thalassaemia intermedia
  3. beta thalassaemia major
28
Q

presentation of beta thalassaemia trait

A

asymptomatic
no/mild anaemia
low MCV/MCH

29
Q

what is diagnostic of beta thalassaemia trait?

A

raised HbA2

30
Q

presentation of beta thalassaemia major

A 
6-24 months
pallor
failure to thrive
hepatosplenomegaly
skeletal changes
organ damage
31
Q

how are beta thalassaemia intermedia and beta trait different?

A 
trait= one reduced/ absent
intermedia= both reduced or one reduced, one absent
32
Q

what causes hepatosplenomegaly, skeletal changes and organ damage in beta thalassaemia major

A

extramedullary haematopoiesis

33
Q

complication of extramedullary haematopoiesis

A

spinal cord compression

34
Q

diagnosis of beta thalassaemia major

A

mainly HbF and no HbA

hair on end skull XR

35
Q

management of beta thalassaemia major

A

regular transfusions

bone marrow transplant

36
Q

why are regular transfusions carried out in beta thalassaemia major?

A

maintain Hb 95-105g/l
suppress ineffective erythropoiesis
inhibit overabsorption of iron

37
Q

endocrine complications of iron overload

A

impaired growth
hypogonadism
diabetes
OP

38
Q

cardiac disease complications of iron overload

A

cardiomyopathy

arrhythmias

39
Q

liver disease complications of iron overload

A

cirrhosis

hepatocellular carcinoma

40
Q

why can iron overload cause sepsis?

A

bacteria likes iron

41
Q

management of iron overload in haemoglobinopathies

A

iron chelating drugs e.g. desferrioxamine

not venesection as already anaemic

42
Q

cause of sickling disorders

A

point mutation in codon 6 of the beta globin chain that substitutes glutamine to valine producing Bs.
altered structure resulting in HbS

43
Q

what does HbS do when exposed to low oxygen levels?

A

polymerises

44
Q

classification of sickling disorders

A
  • sickle cell trait (HbAS)
  • sickle cell anaemia
  • sickle cell disease
45
Q

what is sickle cell trait?

A

one normal and one abnormal beta gene

46
Q

presentation of sickle cell trait

A

asymptomatic as HbS level too low to polymerise

47
Q

diagnosis of sickle cell trait

A

blood film mainly HbA and HbS <50%

48
Q

what is sickle cell anaemia?

A

two abnormal beta cells

49
Q

diagnosis of sickle cell anaemia

A

HbS >80% and no HbA

50
Q

what is sickle crisis?

A

episode of tissue infarction due to vascular occlusion

51
Q

why is there chronic haemolysis in sickle cell anaemia?

A

shortened RBC lifespan

52
Q

why is there hyposplenism in sickle cell anaemia?

A

splenic infarcts

53
Q

what is sickle cell disease?

A

compound heterozygosity for HbS and another beta chain mutation e.g. HbS/ beta thalassaemia or HbSC disease (two types of B variants)

54
Q

precipitants of sickle crisis

A 
hypoxis
dehydration
infection
cold exposure
stress
fatigue
55
Q

management of sickle crisis

A

opiate analgesia for severe pain
hydration, rest, oxygen, antibiotics if infection
red cell exchange in severe crisis (venesect > transufse > venesect > transfuse)

56
Q

diagnosis of sickling disorders

A 
FBC, Hb, red cell indices, blood film
ethnic origin
HPLC or electrophoresis for abnormal HbS
raised HbA2 in beta trait
antenatal screening
57
Q

management of hyposplenism

A

prophylactic antibiotics

vaccines

58
Q

management of sickling disorders

A

hyposplenism management
folic acid supplements (increased RBC turnover increases demand)
hydroxycarbamide induces HbF production
regular transfusions

Haematology (34 decks)

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