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Haematology > Haemoglobinopathy > Flashcards

Haemoglobinopathy Flashcards

1
Q

What are the major forms of haemoglobin?

A

HbA
HbA2
HbF

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2
Q

HbA2 contains what globin chains?

A

2 x alpha

2 x delta

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3
Q

Control of alpha globin chain production occurs on which chromosome?

A

16

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4
Q

How many alpha genes are present per chromosome?

A

2

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5
Q

Control of beta globin chain production occurs on which chromosome?

A

11

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6
Q

How many beta genes are present per chromosome?

A

1

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7
Q

At what age does one reach adult levels of haemoglobin?

A

6-12 months

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8
Q

What are the two main groups of haemoglobinopathies?

A

Thalassaemia

Structural haemoglobin variants

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9
Q

What occurs in thalassaemia?

A

There is decreased rate of globin chain synthesis

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10
Q

Inadequate haemoglobin production due to thalassaemia will cause what type of anaemia?

A

Microcytic (hypochromic)

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11
Q

The accumulation of globin chains can be toxic to what?

A

Bone marrow - causes ineffective erythropoeisis

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12
Q

How many alpha genes have been deleted in an alpha + thalassaemia?

A

One

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13
Q

How many alpha genes have been deleted in an alpha 0 thalassaemia?

A

Both

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14
Q

How many genes are missing if a patient has an alpha thal trait?

A

One or two (alpha + / alpha; alpha 0 / alpha; alpha + / alpha +)

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15
Q

Having only one alpha gene present results in what condition?

A

HbH disease

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16
Q

What occurs in Hb Bart’s hydrops fetalis?

A

When there are no functional alpha genes present

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17
Q

Do patients with the alpha thal trait need treated?

A

No - asymptomatic

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18
Q

What are haemoglobin, MCV and MCH levels like in HbH disease?

A

Low - very low MCV and MCH

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19
Q

What happens to the excess beta chains in HbH disease?

A

They form HbH tetramers which cannot carry oxygen

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20
Q

Give some clinical features of HbH disease

A

Moderate anaemia
Splenomegaly
Jaundice

21
Q

Where is HbH disease particularly common?

A

SE Asia
Middle East
Mediterranean

22
Q

Why is it so significant to have no alpha genes present?

A

As neither HbA or HbF can be made

23
Q

Give some clinical features of Hb Bart’s hydrops fetalis

A

Severe anaemia
Cardiac failure
Hepatosplenomegaly
Skeletal/CV abnormalities

24
Q

Is Hb Bart’s hydrops fetalis compatible with life?

A

No

25
Q

What type of mutations will cause beta thalassaemia?

A

Point

26
Q

What are the classifications of beta thalassaemia?

A

Beta thalassaemia trait
Beta thalassaemia intermedia
Beta thalassaemia major

27
Q

Are patients with the beta thalassaemia trait symptomatic?

A

No

28
Q

What is the diagnostic feature of beta thalassaemia trait?

A

Raised HbA2

29
Q

When does beta thalassaemia major present? Why?

A

6-24 months - level of HbF falls

30
Q

Give some clinical features of beta thalassaemia major

A

Pallor
Failure to thrive
Hepatosplenomegaly
Bone deformities

31
Q

How is beta thalassaemia major managed?

A

Regular transfusion

32
Q

What is the main danger of regular transfusion in beta thalassaemia patients?

A

Iron overload - main cause of death

33
Q

Give some effects of iron overload in transfused patients

A 
Endocrine dysfunction (diabetes/osteoporosis)
Cardiac disease (cardiomyopathy)
Liver disease (cirrhosis)
34
Q

What is used to manage iron overload?

A

Iron chelating drugs (desferrioxamine)

35
Q

How do iron chelators work?

A

They bind to the iron and form complexes which are excreted in urine/stool

36
Q

What genetic change occurs in sickling disorders?

A

A point mutation in the beta globin gene substituting glutamine to valine

37
Q

What effect does the point mutation have on haemoglobin?

A

It alters the structure of Hb to HbS

38
Q

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

A

It polymerises and damages the RBC membrane

39
Q

Are people with sickle trait symptomatic?

A

No - unless exposed to severe hypoxia (high altitude etc.)

40
Q

Patients with sickle cell anaemia have two faulty beta chains. True/false?

A

True - HbSS

41
Q

What occurs in a sickle cell crisis?

A

There are episodes of tissue infarction due to vascular occlusion

42
Q

Give some features of sickle cell anaemia

A

Chronic haemolysis
Hyposplenism
Pain (sickle crisis)

43
Q

Give some causes of sickle crisis

A 
Hypoxia
Dehydration
Infection
Cold exposure
Stress
44
Q

How is sickle crisis treated?

A 
Opiate analgesia
Hydration
Rest
Oxygen
Red cell exchange transfusion (severe crises)
45
Q

What is involved in the long-term management of sickle cell anaemia?

A

Prophylactic penicillin/vaccination (hyposplenism)
Folate supplementation
Hydroxycarbamide
Transfusion

46
Q

How does hydroxycarbamide work?

A

It induces HbF production

47
Q

What technique is used to diagnose haemoglobinopathy?

A

HPLC

48
Q

What can HPLC identify?

A 
Abnormal haemoglobin (Hbs)
Raised HbA2 (beta thal trait)

Haematology (19 decks)

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