Haemoglobinopathy Flashcards Preview

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Flashcards in Haemoglobinopathy Deck (33)
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1

Describe the structure of haemoglobin

Tetramer
4 globin chains
One haem group attached to each globin chain

2

What are the 3 main forms of haemoglobin?

HbA: (2-alpha, 2-beta)
HbA2: (2-alpha, 2-delta)
HbF: (2-alpha, 2-gamma)

3

The genes making the alpha protein for haemoglobin are located on which chromosome? How many alpha genes are on each chromosome?

Chromosome 16
2 alpha genes per chromosome

4

The genes making the beta protein for haemoglobin are located on which chromosome? How many beta genes are on each chromosome?

Chromosome 11
1 beta gene per chromosome

5

Which type of haemoglobin - HbA, HbA2 or HbF - is found in a foetus?

HbF

6

When does foetal haemoglobin typically reach adult level following birth?

6-12 months

7

What are haemoglobinopathies?

Hereditary conditions affecting globin chain synthesis

8

What inheritance pattern do haemoglobinopathies generally follow?

Autosomal recessive

9

What are the 2 main groups of haemoglobinopathies?

Thalassaemias
Structural variant

10

What is the problem in thalassaemias?

Decreased rate of globin chain synthesis, resulting in less haemoglobin

11

What is the problem in structural variant haemoglobinopathy?

Normal production of structurally abnormal globin chains, resulting in variant haemoglobin

12

Alpha thalassaemia (affecting alpha-chain synthesis) results from deletion of how many - one or both - alpha genes from chromosome 16?

Either! Can arise due to deletion of one alpha gene or both alpha genes

13

What are the 3 classifications of alpha thalassaemia?

Trait: 1 or 2 genes missing
HbH: 1 alpha gene left
Bart's hydrops fetalis: no alpha genes

14

Alpha thalassaemia trait is usually asymptomatic. True/False?

True
Mild anaemia and may be mistaken for iron deficiency

15

Describe the clinical features of HbH alpha thalassaemia

Anaemia
Very low MCV
Splenomegaly
Jaundice
Growth retardation

16

What can be seen on special staining of red cells in HbH alpha thalassaemia?

Red cell inclusions (HbH bodies)

17

Describe the clinical features of Bart's hydrops fetalis alpha thalassaemia

Severe anaemia (can't make Hb)
Cardiac failure
Oedema
Growth retardation
Hepatosplenomegaly
Skeletal abnormality
Death in utero

18

Beta thalassamia only affects beta chains, thus which type of haemoglobin production is affected?

Only affects HbA production

19

What type of mutations are typical in alpha and beta thalassaemias respectively?

Alpha thalassaemia typically due to deletions
Beta thalassaemia typically due to point mutations

20

What are the 3 classifications of beta thalassaemia?

Trait: no or 1 gene missing
Intermedia: 1 gene missing
Major: 2 genes missing

21

What are the laboratory features of beta thalassaemia major?

Very low MCV
Microcytosis, hypochromia
Anisopoikilocytosis
Target cells

22

Beta thalassaemia major is transfusion dependent. True/False?

True

23

Severe thalassaemia can cause extramedullary haematopoiesis. What are the consequences of this?

Hepatosplenomegaly
Skeletal changes
Organ damage
Cord compression

24

What becomes the main cause of mortality from transfusion treatment for beta thalassaemia major?

Iron overload

25

How can iron overload secondary to transfusion be managed?

250mg of iron per unit of red cells
Iron-chelating drug (desferrioxamine)

26

What is the best method of diagnosing thalassaemia? What does it show?

High performance liquid chromatography (HPLC)
Quantifies Hb present and identifies abnormal Hb

27

What is the pathophysiology of sickle cell disorder?

Point mutation in codon 6 of beta-globin gene, causing valine production instead of glutamine, altering the structure of Hb to produce HbS

28

What is the genetic makeup of sickle-cell trait?

One normal beta gene, one abnormal beta gene

29

Is sickle cell anaemia autosomal dominant or recessive?

Autosomal recessive
Requires 2 abnormal beta genes

30

What is a sickle crisis?

Episodes of tissue infarction due to vascular occlusion by sickle cells