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Haematology Week 1 > Haemoglobinopathy > Flashcards

Haemoglobinopathy Flashcards

1
Q

What type of globin chains make up each of the following types of Hb: a) HbA? b) HbA2? c) HbF?

A

a) 2x alpha and 2x beta b) 2x alpha and 2x delta c) 2x alpha and 2x gamma

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2
Q

On which chromosome are the genes for alpha globin chains? How many of these genes are in 1 chromosome?

A

Chromosome 16 / 2 genes per chromosome (making 4 per cell)

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3
Q

On which chromosome are the genes for beta globin chains? How many of these genes are in 1 chromosome?

A

Chromosome 11 / 1 gene per chromosome (making 2 per cell)

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4
Q

When are adult levels of Hb usually reached?

A

By 6-12 months of age

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5
Q

What are haemoglobinopathies?

A

Hereditary conditions affecting globin chain synthesis

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6
Q

How are haemoglobinopathies usually inherited?

A

Autosomal recessive

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7
Q

What are the two main groups of haemoglobinopathies and what do each of these cause?

A

Thalassaemias, where the amount of globin chain produced is decreased / structural Hb variants, where structurally abnormal globin chains are produced

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8
Q

What defines a thalassaemia?

A

Decreased globin chain production resulting in impaired Hb production

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9
Q

What are the two main types of thalassaemia?

A

Alpha and beta

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10
Q

Inadequate Hb production in thalassaemias leads to what type of anaemia?

A

Microcytic, hypochromic

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11
Q

In thalassaemias, there is an unbalanced accumulation of one type of globin chain (due to decreased production of the other) - what does this lead to?

A

Ineffective erythropoiesis which is toxic, causing haemolysis

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12
Q

Where are cells haemolysed in thalassaemias?

A

In the bone marrow, before they even enter the circulation

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13
Q

In what areas of the world are thalassaemias more common?

A

Southern Europe, Southern Asia and Africa

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14
Q

What causes alpha thalassaemia?

A

Mutations affecting alpha globin chain synthesis

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15
Q

Unaffected individuals should have how many normal alpha genes? Alpha thalassaemia results from what?

A

4 / having a deletion of one or both alpha genes from chromosome 16

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16
Q

What forms of Hb are affected by alpha thalassaemia?

A

All forms (HbA, HbA2, HbF)

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17
Q

How many alpha genes are deleted to cause a) alpha thalassaemia trait? b) HbH disease? c) Hb Bart’s hydrops foetalis?

A

a) 1 or 2 b) 3 c) 4

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18
Q

How many functional alpha genes must there be in the cell to have alpha thalassaemia trait?

A

2 or 3

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19
Q

How does alpha thalassaemia trait present? How is it treated?

A

Usually asymptomatic, potentially mild anaemia - no treatment needed

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20
Q

If alpha thalassaemia trait was to cause anaemia, what type would it cause?

A

Microcytic, hypochromic

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21
Q

How is anaemia from alpha thalassaemia trait differentiated from iron deficiency?

A

In ATT, the ferritin will be normal

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22
Q

How many functional alpha genes are there is HbH disease?

A

One

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23
Q

In HbH disease, there are excess beta chains. What do these do?

A

They form tetramers known as HbH which cannot carry oxygen

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24
Q

How can HbH be visualised? What does it look like?

A

On special stains, look like golf balls

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25
Q

What is the range of clinical presentation of HbH disease?

A

Moderate anaemia - transfusion dependent

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26
Q

What feature of HbH disease may arise as a result of a) extramedullary haemopoiesis? b) haemolysis and ineffective haemopoiesis?

A

a) splenomegaly b) jaundice

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27
Q

Apart from splenomegaly and jaundice, what are some other features which may occur in HbH disease?

A

Growth retardation, gallstones and iron overload

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28
Q

What are the treatment options for severe causes of HbH disease?

A

Splenectomy +/- tranfusion

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29
Q

What type of globin chains make up each of the following types of Hb seen in bart’s hydrops foetalis: a) Hb Barts’? b) HbH?

A

a) 4 x delta chains, b) 4 x beta chains

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30
Q

What will a blood film of Bart’s hydrops foetalis show?

A

Numerous nucleated red cells in the peripheral blood

31
Q

What happens to most sufferer’s of Bart’s hydrops foetalis?

A

Die in utero (pretty much incompatible with life)

32
Q

If a baby does survive with Bart’s hydrops foetalis, what are some potential clinical features?

A

Severe anaemia, cardiac failure, growth retardation, hepatosplenomegaly

33
Q

What type of Hb is affected by beta thalassaemia?

A

HbA

34
Q

What defects in the beta chains causes beta thalassaemia trait?

A

1 reduced or 1 absent beta chain with 1 normal beta chain

35
Q

What defects in the beta chains causes beta thalassaemia intermedia?

A

2 reduced beta chains or 1 absent and 1 reduced beta chain

36
Q

What defects in the beta chains causes beta thalassaemia major?

A

2 absent beta chains

37
Q

What is the clinical picture of beta thalassaemia trait?

A

Asymptomatic, may be mild anaemia

38
Q

What is the clinical picture of beta thalassaemia intermedia?

A

Moderate severity anaemia, requiring occasional transfusions

39
Q

What is the clinical picture of beta thalassaemia major?

A

Severe, lifelong transfusion dependency

40
Q

When and how does beta thalassaemia major usually present?

A

Aged 6-24 months (as HbF falls) with failure to thrive and pallor

41
Q

As beta thalassaemia major progresses, it can cause extramedullary haemopoiesis which can lead to what clinical features?

A

Hepatosplenomegaly, skeletal changes (potential spinal cord compression), end organ damage

42
Q

What will Hb analysis of someone with beta thalassaemia major show?

A

Mainly HbF, minimal MbA

43
Q

What is the treatment for beta thalassaemia major? What is the main complication of this?

A

Blood transfusions / iron overload

44
Q

What can be a treatment for beta thalassaemia major if detected before major complications develop?

A

Bone marrow transplant

45
Q

What are some endocrine consequences of iron overload?

A

Impaired growth and puberty, diabetes, osteoporosis

46
Q

What are some cardiac consequences of iron overload?

A

Cardiomyopathy and arrhythmias

47
Q

What are some liver consequences of iron overload?

A

Cirrhosis and hepatocellular carcinoma

48
Q

Why is venesection not a feasible treatment of iron overload as a result of transfusions for beta thalassaemia major?

A

These inidviduals are already anaemic

49
Q

What is the treatment for iron overload as a result of transfusions for beta thalassaemia major?

A

Iron chelating drugs (IV/SC)

50
Q

Apart from iron overload, what are some other complications of transfusions given in beta thalassaemia major?

A

Infections, alloantibodies, transfusion reactions, increased risk of sepsis

51
Q

How do sickling disorders come about?

A

They are caused by a point mutation at codon 6 on the beta globin gene

52
Q

What substitution occurs as a result of the mutation causing sickling disorders? What does this produce?

A

Glutamine - valine / Beta S

53
Q

In sickling disease, the structure of Hb changes to HbS - what chains make up HbS?

A

2 x alpha, 2 x beta S

54
Q

What happens if HbS is exposed to low oxygen levels for a prolonged period?

A

It polymerises, which distorts the red cell and damages the membrane

55
Q

What is the genotype of individuals with sickle trait (HbAS)?

A

1 normal beta chain, 1 abnormal beta S chain

56
Q

When may sickle trait cause problems?

A

At times of low oxygen e.g. high altitude, under anaesthesia

57
Q

Describe the blood film seen in sickle trait? What type of Hb predominantes?

A

Normal / HbA (formed from the normal beta chain)

58
Q

What is the genotype of individuals with sickle cell anaemia (HbSS)?

A

Two abnormal beta S chains

59
Q

What type of Hb predominates in sickle cell anaemia?

A

HbS

60
Q

What is a sickle crisis?

A

Episodes tissue infarction due to vascular occlusion because the distorted cell gets trapped

61
Q

Where are some sites which may be affected by a sickle crisis?

A

Digits, bone marrow, lung, spleen, CNS

62
Q

What are some potential precipitants of a sickle crisis?

A

Hypoxia, dehydration, infection, cold exposure, stress

63
Q

How should a sickle crisis be treated?

A

Opiate analgesia, hydration, oxygen, rest

64
Q

What is a treatment option for a severe sickle crisis?

A

Red cell transfusion

65
Q

What effect does sickle cell anaemia have on the spleen?

A

Causes hyposplenism due to repeated infarcts

66
Q

What are some long term effects of sickle cell anaemia?

A

Impaired growth and risk of end organ damage e.g. leg ulcers, AVN, stroke

67
Q

How should the hyposplenism in sickle cell anaemia be treated?

A

Prophylactic penicillin and vaccination for pneumococcus, meningococcus and haemophilus

68
Q

What are some long term treatments for sickle cell anaemia?

A

Folic acid supplements and hydroxycarbamide

69
Q

What is sickle cell disease?

A

Essentially sickle cell anaemia with another beta chain mutation e.g. beta thalassaemia

70
Q

What investigations can be used to identify the types of Hb present in an individual?

A

High performance liquid chromatography or gel electrophoresis

71
Q

A raised HbA2 is diagnostic of what?

A

Beta thalassaemia trait

72
Q

HPLC is normal in alpha thalassaemia trait - what is needed to confirm this diagnosis?

A

DNA testing

73
Q

If a woman is pregnant, she will get tested to see if she is a carrier of thalassaemia. Does the father ever need to get tested?

A

Only if the mother comes back to be a carrier

Haematology Week 1 (11 decks)

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