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Haematology > Haemaglobinopathies > Flashcards

Haemaglobinopathies Flashcards

1
Q

Name the three types of haemoglobin

A

HbA - two alpha two beta
HbA2 - two alpha two delta
HbF - two alpha two gamma

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2
Q

Where are the alpha globin genes found and how many are there?

A

Chromosome 16 - two per chromosome and four per cell

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3
Q

Where are the beta globulin genes found and how many are there?

A

Chromosome 11 - one per chromosome and two per cell

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4
Q

When does globulin expression reach adult levels?

A

6-12 months

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5
Q

Define haemoglobinopathy

A

Hereditary conditions that affect globulin chain synthesis

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6
Q

What mode of inheritance do haemoglobulinopathies follow?

A

Autosomal recessive

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7
Q

What disease is linked to haemoglobinopathies?

A

Malaria

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8
Q

Name the two groups of haemoglobinopathies

A

Thalassaemias

Structural Hb variants

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9
Q

What is thalassaemia?

A

Reduced globulin chain synthesis and Hb production

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10
Q

What do thalassaemias cause?

A

Microcytic hypochromic anaemia

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11
Q

Name the three variations of alpha thalassaemia

A

Trait
HbH disease
Hb Barts hydrops fetalis

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12
Q

Describe alpha thalassaemia trait

A

One or two missing genes, asymptomatic carrier with microcytic hypochromic red cells but normal ferritin

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13
Q

How does HbH disease arise?

A

Loss of three alpha genes
Moderate to severe anaemia
Excess beta chains form HbH

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14
Q

Where is HbH disease most common?

A

SE asia due to alpha nought endemic

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15
Q

How will HbH present?

A

Jaundice, severe anaemia, splenomegaly

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16
Q

When may patients with HbH require a transfusion?

A

During acute illness

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17
Q

What genetic issues leads to Hb Barts hydrops fetalis?

A

No functional genes - incompatible with life
Excess beta chains form HbH
Excess gamma chains form Hb Barts

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18
Q

How will Hb Barts hydros fetalis present?

A

Profound anaemia, cardiac failure, hepatosplenomegaly, growth retardation, skeletal abnormalities

19
Q

What types of Hb are beta chains present?

20
Q

Name three beta thalamassamias

A

Trait
Intermedia
Major

21
Q

Describe beta thalassaemia trait

A

Asymptomatic, no/mild anaemia due to one abnormal copy of the gene

22
Q

What is the genetic cause of beta thalassaemia intermedia?

A

Two defective genes

One defective gene and one deletion

23
Q

How will beta thalassaemia intermedia present?

A

Moderate severity - microcytic hypochromic anaemia need regular monitoring and may need transfusion

24
Q

What is the genetic cause of beta thalassaemia major?

A

Two deletion genes

25
Q

How does beta thalassaemia major present?

A 
Severe microcytic hypochromic anaemia 
Hepatosplenomegaly 
Skeletal deformity 
Failure to thrive 
Palor
26
Q

At what age does beta thalassaemia major commonly present?

A

6-24 months

27
Q

What happens to the Hb in beta thalassaemia major?

A

No HbA, mainly HbF

28
Q

Why do you see skeletal deformity in beta thalassaemia major?

A

Extramedullary haematopoiesis

29
Q

What skeletal changes are classical of beta thalassaemia major?

A

Frontal bossing

Hair on end skull x-ray

30
Q

How is beta thalassaemia major managed?

A

Regular transfusion

31
Q

What is the major risk of regular transfusion?

A

Iron overload

32
Q

What are the consequences of iron overload?

A

Endocrine dysfunction - diabetes, osteoporosis
Cardiac Disease - arrhythmias, cardiomyopathy
Liver Disease - cirrhosis, cancer
Sepsis

33
Q

What drug can be given with transfusion to prevent overload?

A

Iron chelating drugs

34
Q

How do sickling disorders arise?

A

Point mutations in beta globulin gene cause glutamine to change to valine and produce HbS

35
Q

What happens to HbS?

A

It can polymerise if exposed to low oxygen levels for a prolonged time with distorts the red cell and damages the membrane

36
Q

What is sickle cell trait?

A

Asymptomatic carrier state, generally HbS levels are too low to have an effect

37
Q

What does sickle cell anaemia cause?

A

Episodes of tissue infarction due to microvascular occlusion

38
Q

How does sickle cell crisis present?

A

Severe pain due to ischaemia and inflammation

39
Q

What is the effect of sickle cell on the spleen?

A

Chronic haemolysis due to distorted red cells, shorter life span - sequestered in the spleen causing splenic infarcts and hyposplenism

40
Q

What can precipitate a sickle cell crisis?

A

Hypoxia, dehydration, infection, stress, fatigue

41
Q

How is sickle cell crisis treated?

A

Opiate, hydrate, oxygen, red cell exchange transfusion if severe crisis

42
Q

How is sickle cell anaemia managed long term?

A

Hyposplenism - prophylactic penicillin and vaccination
Folic Acid Supplement
Hydroxycarbamide - induces HbF production
Regular transfusion therapy

43
Q

What is the most common technique for diagnosing thalassaemia?

A

High power liquid chromatography

Haematology (18 decks)

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