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Haemoglobinopathies Flashcards

(58 cards)

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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

Study These Flashcards
A

antenatal screening

risk increased if both parents from SE Asia

25
common cause of beta thalassaemia
point mutations
26
which Hb is affected in beta thalassaemia?
only HbA
27
classification of beta thalassaemia
1. beta thalassaemia trait 2. beta thalassaemia intermedia 3. beta thalassaemia major
28
presentation of beta thalassaemia trait
asymptomatic no/mild anaemia low MCV/MCH
29
what is diagnostic of beta thalassaemia trait?
raised HbA2
30
presentation of beta thalassaemia major
``` 6-24 months pallor failure to thrive hepatosplenomegaly skeletal changes organ damage ```
31
how are beta thalassaemia intermedia and beta trait different?
``` trait= one reduced/ absent intermedia= both reduced or one reduced, one absent ```
32
what causes hepatosplenomegaly, skeletal changes and organ damage in beta thalassaemia major
extramedullary haematopoiesis
33
complication of extramedullary haematopoiesis
spinal cord compression
34
diagnosis of beta thalassaemia major
mainly HbF and no HbA | hair on end skull XR
35
management of beta thalassaemia major
regular transfusions | bone marrow transplant
36
why are regular transfusions carried out in beta thalassaemia major?
maintain Hb 95-105g/l suppress ineffective erythropoiesis inhibit overabsorption of iron
37
endocrine complications of iron overload
impaired growth hypogonadism diabetes OP
38
cardiac disease complications of iron overload
cardiomyopathy | arrhythmias
39
liver disease complications of iron overload
cirrhosis | hepatocellular carcinoma
40
why can iron overload cause sepsis?
bacteria likes iron
41
management of iron overload in haemoglobinopathies
iron chelating drugs e.g. desferrioxamine not venesection as already anaemic
42
cause of sickling disorders
point mutation in codon 6 of the beta globin chain that substitutes glutamine to valine producing Bs. altered structure resulting in HbS
43
what does HbS do when exposed to low oxygen levels?
polymerises
44
classification of sickling disorders
- sickle cell trait (HbAS) - sickle cell anaemia - sickle cell disease
45
what is sickle cell trait?
one normal and one abnormal beta gene
46
presentation of sickle cell trait
asymptomatic as HbS level too low to polymerise
47
diagnosis of sickle cell trait
blood film mainly HbA and HbS <50%
48
what is sickle cell anaemia?
two abnormal beta cells
49
diagnosis of sickle cell anaemia
HbS >80% and no HbA
50
what is sickle crisis?
episode of tissue infarction due to vascular occlusion
51
why is there chronic haemolysis in sickle cell anaemia?
shortened RBC lifespan
52
why is there hyposplenism in sickle cell anaemia?
splenic infarcts
53
what is sickle cell disease?
compound heterozygosity for HbS and another beta chain mutation e.g. HbS/ beta thalassaemia or HbSC disease (two types of B variants)
54
precipitants of sickle crisis
``` hypoxis dehydration infection cold exposure stress fatigue ```
55
management of sickle crisis
opiate analgesia for severe pain hydration, rest, oxygen, antibiotics if infection red cell exchange in severe crisis (venesect > transufse > venesect > transfuse)
56
diagnosis of sickling disorders
``` FBC, Hb, red cell indices, blood film ethnic origin HPLC or electrophoresis for abnormal HbS raised HbA2 in beta trait antenatal screening ```
57
management of hyposplenism
prophylactic antibiotics | vaccines
58
management of sickling disorders
hyposplenism management folic acid supplements (increased RBC turnover increases demand) hydroxycarbamide induces HbF production regular transfusions

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