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haematology > haemoglobinopathies > Flashcards

haemoglobinopathies Flashcards

1
Q

How many haem groups on each globin chain?

A

1

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2
Q

Hb is a tetramer made up of how many aloha and beta chains?

A

2 alpha 2 beta

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3
Q

what is the major form of haemoglobin present in adults?

A

HbA

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4
Q

what types of chain are in HbA2?

A

a2d2

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5
Q

which chromosome are alpha genes on?

A

16

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6
Q

how may alpha genes are there per cell?

A

2 per chromosome (4 per cell)

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7
Q

beta like genes are on chromosome?

A

11 (believe)

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8
Q

what age are is adult haemoglobin present?

A

6-12 months of age

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9
Q

what are haemoglobinopathies?

A

hereditary conditions affecting globin chain synthesis

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10
Q

What is the difference between thalassaemias and structural haemoglobin variants?

A

thalassaemias are decreased rate of globin chain synthesis. structural haemoglobin variants are normal production of structurally abnormal globin chain e.g.. HbS

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11
Q

two types of thalassaemia?

A

alpha and beta

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12
Q

what type of anaemia do you get in thalassaemia?

A

microcytic hypochromic

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13
Q

why would you get ineffective erythropoiesis and haemolysis?

A

you get unbalanced accumulation of globin chains which is toxic.

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14
Q

(αα/αα). If someone has four normal a genes, will they be normal?

A

unaffected

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15
Q

what mutations can you get on chromosome 16 to cause alpha thalassaemia?

A

deletion of one or both alpha genes from chromosome 16

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16
Q

why is losing ability to produce alpha chains so important?

A

they are present in all forms of Hb

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17
Q

what is alpha thalassaemia trait?

A

having one or two genes missing from the 4

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18
Q

how many alpha genes do you have in HbH disease?

A

only 1 left

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19
Q

how many functional alpha genes do you have left in Hb barts hydrous fettles?

A

none (no functional alpha genes) (–/–)

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20
Q

In alpha thalasaemia trait, patient is asymptomatic with microcytic hypo chromic red cells. is any treatment needed?

A

no

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21
Q

In which disease do beta chains form tetramers which can’t carry oxygen?

A

HbH disease

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22
Q

red cell inclusions of what can be seen with special stains?

A

HbH

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23
Q

what are MCV and MCH levels like in HbH?

A

very low

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24
Q

why do you get jaundice in HbH?

A

haemolysis and ineffective erythropoiesis

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25
Q

what do severe cases of HbH need?

A

splenectomy and transfusion

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26
Q

what is the severest for of alpha thalassaemia?

A

Hb barts hydrops fetalis (no alpha gene inherited from either parent (–/–)

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27
Q

what happens to HbA in parts hydrous fetalis?

A

it can’t be made

28
Q

clinical features of hb barts hydrops fetalis?

A

severe anaemia, cardiac failure, growth retardation, severe hepatosplenomegaly, skeletal and cardiovascular abnormalities

29
Q

what is the outcome of hb barts hypos fetalis?

A

almost all die in utero

30
Q

Beta thalassaemias are usually casued by?

A

point mutations

31
Q

what is the only type of haemoglobin affected in beta thalassaemia?

A

HbA (a2b2)

32
Q

why would you get a raised HbA2 in beta thalassaemia trait?

A

can’t produce beta chains so can’t produce HbA

33
Q

3 classifications of beta thalassaemia?

A

trait, intermedia and major

34
Q

when do patients with b thalassaemia major present?

A

6-24 months old (as HbF falls off)

35
Q

on hb analysis in b thalassaemia major, what would you see?

A

mainly HbF, minimal HbA

36
Q

in b thal major, you get extra medullary haematopoesis causing?

A

hepatosplenomegaly, skeletal changes and organ damage

37
Q

management of b thalassaemia major?

A

regular transfusion programme to maintain Hb at 95-105

38
Q

what is the main cuase of mortality in b thal major?

A

iron overload from transfusion

39
Q

what are the consequences of iron overload?

A

endocrine dysfunction, cardiac disease, liver disease

40
Q

why do you get iron overload in transfusion?

A

250mg of iron per unit of red cells. chronic anaemia drives increased iron absorption.

41
Q

what are iron chelating drugs. example of one?

A

they bind to iron and form complexes which are excreted in urine or stool

42
Q

why do you get increased risk of sepsis with iron?

A

bacteria like iron

43
Q

why do you get sickling disorders?

A

point mutation in b globin gene that substitutes glutamine to valine producing Bs

44
Q

what haemoglobin do you get in sickle cells ?

A

A2Bs2

45
Q

what happens to HbS if its exposed to low oxygen concentrations for long periods?

A

polymerises. This distorts the red cell, damaging the rbc membrane

46
Q

sickle cell trait is an asymptomatic carrier state. when would they sickle?

A

in severe hypoxia e.g. high altitude or under anaesthesia

47
Q

The blood film is normal. what is the percentage of HbS?

A

less than 50%

48
Q

in sickle cell anaemia (HbSS) you have 2 abnormal beta genes. what inheritance is this?

A

autosomal recessive

49
Q

mode of inheritance of von willebrands disease?

A

autosomal dominant

50
Q

levels of HbS?

A

> 80%

51
Q

what is sickle cell crisis?

A

Episodes of tissue infarction due to vascular occlusion

52
Q

levels of HbA in sickle cell?

A

0

53
Q

what happens to sickled red blood cells?

A

they are sequestrated in liver and spleen

54
Q

why do you get hyposplenism ?

A

repeated splenic infarcts

55
Q

why would you get tissue infarction and extreme pain?

A

sickle cell vaso occlusion

56
Q

precipitants of sickle cell crisis?

A 
hypoxia
dehydration
infection 
cold exposure 
stress/fatigue
57
Q

treatment of painful crisis

A 
Opiate analgesia 
Hydration 
Rest
Oxygen 
Antibiotics if evidence of infection 
Red cell exchange transfusion in severe crises eg chest crisis or neurological symptoms
58
Q

why do you need folic acid supplementation in sickle cell?

A

increased cell turnover so increased demand

59
Q

what does hyposplenism do to risk of infection?

A

increases risk of infection

60
Q

what tests can you do to quantify haemoglobin present?

A

High performance liquid chromatography (HPLC) or gel electrophoresis

61
Q

Raised HbA2 diagnostic of?

A

b thalassaemia trait

62
Q

HPLC normal in?

A

alpha thal trait so DNA testing needed to confirm

63
Q

Microcytic hypochromic RBCs not always due to iron deficiency

A

y

64
Q

what is the pathophysiology of G6PD deficiency?

A

Reduced G6PD reduced glutathione increased red cell susceptibility to oxidative stress

65
Q

what can cause G6PD?

A

drugs such as ciprofloxacin, anti malarial and sulph group drugs such as SUs

66
Q

what is the sign seen on blood film in G6PD deficiency?

A

heinz bodies

haematology (20 decks)

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