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KB - Haematology > Haemoglobinopathies > Flashcards

Haemoglobinopathies Flashcards

1
Q

What is the structure of haemoglobin?

A

tetramer of 2 alpha and 2 beta globin chains
1 haem group attached to each globin chain
each contains an Fe2+ ion

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2
Q

What are the major forms of Hb?

A

HbA - 2 alpha, 2 beta
HbA2 - 2 alpha, 2 delta
HbF - 2 alpha, 2 gamma

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3
Q

What are the thalassaemias?

A

genetic diseases with under production or no production of one globin chain

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4
Q

What does unbalanced accumulation of globin chains cause?

A

It is toxic

Ineffective erythropoiesis and haemolysis

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5
Q

What kind of anaemia do you get in thalassaemias?

A

microcytic and hypo chromic (as inadequate Hb production)

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6
Q

What are the classifications of alpha thalassaemias?

A

unaffected
a thalassaemia trait
HbH disease
Hb Barts hydrops fetalis

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7
Q

What are a thalassaemias?

A

deletion of one (-a) or both (–) a genes from chromosome 16

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8
Q

What is Hb Barts hydrops fetalis?

A 
death occurs in utero 
all 4 a genes are deleted 
--/--  
(should be aa/aa)
HbA can't be made
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9
Q

What is HbH disease?

A

3 genes deleted

–/-a

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10
Q

What is a thalassaemia trait?

A 
1 or 2 genes missing 
(aa/-a) 
(--/aa) 
(a-/a-) 
asymptomatic, no treatment
decreased MCV
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11
Q

What are the clinical features of HbH disease?

A

moderate anaemia, features of haemolysis
hepatosplenomegaly
leg ulcers
jaundice

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12
Q

What is HbH in HbH disease?

A 
excess B chains form tetramers (B4) 
called HbH (can't carry oxygen)
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13
Q

What are B thalassaemias?

A

disorder of B chain synthesis

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14
Q

What are the classifications of B thalassaemias?

A

B thalassaemia trait
B thalassaemia intermedia
B thalassaemia major

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15
Q

What is B thalassaemia trait?

A

B-/BB
asymptomatic, no or mild anaemia
decreased MCV

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16
Q

What is B thalassaemia intermedia?

A

B-/B-
moderate anaemia
splenomegaly

17
Q

What usually causes B thalassaemias?

A

point mutations in B globin genes on chromosome 11

18
Q

What Hb is affected in B thalassaemia?

A

only HbA

19
Q

What Hb is affected in a thalassaemia?

A

HbA
HbA2
HbF
(all)

20
Q

What is B thalassaemia major?

A

(–/–) - no B genes

lifelong transfusion dependency

21
Q

What is the management of B thalassaemia major?

A

regular transfusion

watch for iron overload (give iron chelating drugs e.g. desferroxamine)

22
Q

How is reduced B or a written?

A

B+

a+

23
Q

How is absent B or a written?

A

B0
a0
(small zero)

24
Q

How does B thalassaemia major present?

A

first year of life

severe anaemia and failure to thrive

25
Q

What is sickle cell anaemia?

A

autosomal recessive disorder

production of abnormal B chains

26
Q

What is the mutation in sickle cell anaemia?

A

point mutation - codon 6 of B globin gene
substitutes glutamine for valine
produces HbS not HbA

27
Q

What is the pathogenesis of sickle cell anaemia?

A

HbS polymerises when deoxygenated
RBCs deform producing sickle cells
fragile and haemolyse
also block small vessels

28
Q

What is sickle trait?

A

one normal, one abnormal B gene (B/Bs)

asymptomatic carrier state

29
Q

When may someone with sickle trait experience symptoms of sickling?

A

in severe hypoxia e.g. anaesthesia, high altitude

30
Q

What is a sickle crisis?

A

episodes of tissue infarction due to vascular occlusion

31
Q

What are the symptoms of a sickle crisis?

A

depends on site and severity
severe pain
e.g. CNS, lung, spleen, bone marrow

32
Q

Why is there hyposplenism in sickle cell anaemia?

A

repeated splenic infarcts

sequestration of sickled RBC in liver and spleen

33
Q

What can trigger a sickle crisis?

A

cold
dehydration
infection
hypoxia

34
Q

What is it called when hands/feet are affected in a sickle crisis?

A

dactylitis

35
Q

What is the long term management of sickle cell anaemia?

A

hydroxycarbimide - if frequent crises
prophylactic penicillin and vaccination - for hyposplenism
folic acid supplements

KB - Haematology (11 decks)

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