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3MB Haematology > Haemoglobinopathy > Flashcards

Haemoglobinopathy Flashcards

1
Q

Describe the structure of haemoglobin

A

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

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2
Q

What are the 3 main forms of haemoglobin?

A

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

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3
Q

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

A

Chromosome 16

2 alpha genes per chromosome

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4
Q

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

A

Chromosome 11

1 beta gene per chromosome

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5
Q

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

A

HbF

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6
Q

When does foetal haemoglobin typically reach adult level following birth?

A

6-12 months

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7
Q

What are haemoglobinopathies?

A

Hereditary conditions affecting globin chain synthesis

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8
Q

What inheritance pattern do haemoglobinopathies generally follow?

A

Autosomal recessive

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9
Q

What are the 2 main groups of haemoglobinopathies?

A

Thalassaemias

Structural variant

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10
Q

What is the problem in thalassaemias?

A

Decreased rate of globin chain synthesis, resulting in less haemoglobin

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11
Q

What is the problem in structural variant haemoglobinopathy?

A

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

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12
Q

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

A

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

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13
Q

What are the 3 classifications of alpha thalassaemia?

A

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

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14
Q

Alpha thalassaemia trait is usually asymptomatic. True/False?

A

True

Mild anaemia and may be mistaken for iron deficiency

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15
Q

Describe the clinical features of HbH alpha thalassaemia

A 
Anaemia
Very low MCV
Splenomegaly
Jaundice
Growth retardation
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16
Q

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

A

Red cell inclusions (HbH bodies)

17
Q

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

A 
Severe anaemia (can't make Hb)
Cardiac failure
Oedema
Growth retardation
Hepatosplenomegaly
Skeletal abnormality
Death in utero
18
Q

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

A

Only affects HbA production

19
Q

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

A

Alpha thalassaemia typically due to deletions

Beta thalassaemia typically due to point mutations

20
Q

What are the 3 classifications of beta thalassaemia?

A

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

21
Q

What are the laboratory features of beta thalassaemia major?

A

Very low MCV
Microcytosis, hypochromia
Anisopoikilocytosis
Target cells

22
Q

Beta thalassaemia major is transfusion dependent. True/False?

A

True

23
Q

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

A

Hepatosplenomegaly
Skeletal changes
Organ damage
Cord compression

24
Q

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

A

Iron overload

25
Q

How can iron overload secondary to transfusion be managed?

A

250mg of iron per unit of red cells

Iron-chelating drug (desferrioxamine)

26
Q

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

A

High performance liquid chromatography (HPLC)

Quantifies Hb present and identifies abnormal Hb

27
Q

What is the pathophysiology of sickle cell disorder?

A

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

28
Q

What is the genetic makeup of sickle-cell trait?

A

One normal beta gene, one abnormal beta gene

29
Q

Is sickle cell anaemia autosomal dominant or recessive?

A

Autosomal recessive

Requires 2 abnormal beta genes

30
Q

What is a sickle crisis?

A

Episodes of tissue infarction due to vascular occlusion by sickle cells

31
Q

List some precipitants of a sickle crisis

A 
Hypoxia
Dehydration
Infection
Cold exposure
Stress
Fatigue
32
Q

Outline treatment of a sickle crisis

A 
Opiate analgesia
Hydration
Rest
Oxygen
Antibiotic if infection
Red cell transfusion if severe
33
Q

What long-term treatment may be given for sickle cell disorder?

A

Penicillin if hyposplenism
Folic acid (increase RBC turnover)
Hydroxycarbamide (induce HbF production)

3MB Haematology (12 decks)

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