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Haematology > Haemaglobinopathy > Flashcards

Haemaglobinopathy Flashcards

1
Q

what is tetramer made up of

A

2 alpha global like chains and 2 beta global like chains

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2
Q

how many haem groups attach to a global chain

A

1:1

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3
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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4
Q

what are the commonest forms of hb

A

HbA - 97%
HbA2 2.5%
HbF 0.5%

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5
Q

genetic control of alpha like genes

A

on chromosome 16

2 alpha genes per chromosome and 4 per cell

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6
Q

genetic control of beta like genes

A

chromosome 11

one beta gene per chromosome - 2/cell

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7
Q

when does expression of global genes change

A

through embryonic life and childhood

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8
Q

how are genes arranged

A

in order of expression

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9
Q

which genes in embryo

A

chromosome 16 - gower1, portland, gower 2

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10
Q

foetal hb

A

hbf

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11
Q

adults hb

A

hba2

hba

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12
Q

when are adult levels reached

A

by 6-12 months of age

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13
Q

what are haemoglobinopathies

A

heredity conditions affecting global chain synthesis

autosomal recessive

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14
Q

what are the two main groups pf hbp

A

thalassaemia - decreased rate of global chain synthesis

structural hb varients - normla production of structural abnormal global chain leading to variant hb such as HbS

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15
Q

types of thalassaemias

A

alpha thalassaemia - alpha chains affected

beta - beta chains affected

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16
Q

what does thalassaemia lead to

A

inadequate hb procuditon leading to microcytic hypochromin anaemia

unbalanced accumulation of global chains leading to ineffective erythropoiesis and haemolysis

17
Q

why are thalassaemias important

A

commonest monogenic disorders
major cause of morbidity
becoming more common in the uk

18
Q

why is thalassaemia more prevalent in certain areas

A

selective pressure in malaria endemic areas has allowed these mutations to flourish

19
Q

what happens during alpha thalassaemia

why

which hb is affected

A

reduced of absence of synthesis of alpha chain

deletion of one or both alpha genes from chromosome 16

alpha chains present in all adult forms of hb are effected - hba, hba2, hbf

20
Q

classification of alpha thalaaaemia

A

unaffected have 4 normal alpha genes

alpha thal trait - one of two genes missing

HbH disease - only one alpha left

Hb Barts hydrops fetales - no functional alpha genes

21
Q 
alpha trait 
symp
rx
signs
why is it important
A

–/aa or -a/-a
asymp

no rx needed

microcytic hypo chromic red cells with mild anaemia

important as can be mistaken for iron defic but ferratin normal and red blood cell count raised

22
Q 
HbH dx
what is it 
chain production 
outcome 
what can be seen on a stain
A

severe form of alpha thalaeeaemia

only one alpha gene per cell so –/-a

alpha chain production is <30% than normal

anaemia with low MCV and MCH
excess beta chains form tetramers beta4 called HbH which can’t carry oxygen

red cell inclusions (HbH bodies) can be seen w special stains

23
Q

clinical features of HbH dx

A

mild anaemia -> transfusion dependant
splenomegaly due to extramedullary haemtopoiesis
jaundice due to haemolytic and inffecetive erythropoiesis
growth retardation
gallstones
iron overload
severe cases - splenectomy+/- transfusion

24
Q

where is HbH common

A

middle east
SE asia
mediterranaean

25
Q

Hb Barts hydrops fetales synd

A

severest form of alpha thallassaemia
no a genes inherited (–/–)
minimal or no alpha chain production -? HbA can’t be made

26
Q

clinical features of Barts

A 
severe anaemia 
cardiac failure, oedema
growth retardation 
severe hepatosplenomegaly
skeletal and cardiovascular abnormalities
most die in utero
27
Q

b thalassaemia is what
caused by what
how many mutations have been identified so far

A

reduced or absent beta chain production
only beta chains so only HbA affected
usually caused by point mutations
over 200 so far

28
Q

classification of BT

A

beta thalassaemia trait - asymp, no or mild anaemia, low MCV and MCH

betal thallasaemia intermdiate - mod serverity requiring occasional transfusion

beta thalassaemia major- severe life long transfusion dependency

29
Q

lab features of beta thal major

A

severe anaemia
reticulocytosis, very low MCV/MCH
film: microcytosis, hypochromia, anisopoikilocytosis and target cells

HPLC: mainly HbF present small amounts of HbA

30
Q

clinical features of beta thal major

A

presents aged 6-24 months
failure to thrive
pallor
extra medullary haemopoiesis causing: hepatosplenomegaly, skeletal damage, organ damage, cord compression

31
Q

management of beta thal major

A

regular transfusion programme to maintain Hb at 95-105g/l to suppress ineffective erythropoiesis and inhibit over absorption of iron

allows for relatively normal growth and development

iron overload from transfusion then becomes the main cause of mortality

bone marrow transplant can be an option if carried out before complications develop

32
Q

clinical features of beta thal major

A

presents aged 6-24 months
failure to thrive
pallor
extra medullary haemopoiesis causing: hepatosplenomegaly, skeletal damage, organ damage, cord compression

33
Q

management of beta thal major

A

regular transfusion programme to maintain Hb at 95-105g/l to suppress ineffective erythropoiesis and inhibit over absorption of iron

allows for relatively normal growth and development

iron overload from transfusion then becomes the main cause of mortality

bone marrow transplant can be an option if carried out before complications develop

34
Q

consequences of iron overload

A

endocrine dysfunction - impaired growth and pubertal development, DM, osteoporosis

cardiac - cardiomyopathy, arrhythmias

liver dx - cirrhosis, herpatocellular cancer

35
Q

management of iron overload

A

250mg of iron per unit of red cells
chronic anaemia -> increased absorption of iron from gut
venesection not feasible as already anaemic
chelators bind to iron, complexes formed excreted in urine or stool

36
Q

what is the natural mechanism for iron excretion

A

there is none

37
Q

other transfusion related complications

A

viral infection - HIV, hep B and C
alloantibodies - hard to crossmatch suitable blood
transfusion reactions

increased risk of bacterial sepsis as bacteria like iron

38
Q

diagnosis of thalassaemia

A

thal trait usually suspected form red cell indices and ethnic origin - exclude iron defic first
blood film: hypochromia, target cells, anisopoikilocytosis

HPLC: Hba, Hba2, Hbf, abnormal hb, raised Hba2 diagnostic for beta thal - will be normal in alpha thal so DNA testing needed to confirm

39
Q

screening for haemoglobinopathies

A

antenatal screening to identify carriers

newborn screening programme for couple at risk

Haematology (26 decks)

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