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Haematology > Haemoglobinopathy > Flashcards

Haemoglobinopathy Flashcards

1
Q

HbA?

A

2 alpha

2 beta

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2
Q

HbA2?

A

2 alpha

2 delta

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3
Q

HbF?

A

2 alpha

2 gamma

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4
Q

What chromosome are alpha genes on?

A

16

2 genes per chromosome

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5
Q

What chromosome are beta genes on?

A

11

One gene per chromosome

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6
Q

What is the pattern of inheritance for haemoglobinopathies?

A

Autosomal recessive

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7
Q

What is a thalassaemia?

A

Reduced glob in chain synthesis, leads to impaired haemoglobin production

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8
Q

Two types of thalassaemia?

A

Alpha

Beta

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9
Q

Alpha thalassaemia is a result of what?

A

Mutations affecting alpha globin chain synthesis

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10
Q

The 3 types of alpha thalassaemia?

A

Trait
HbH disease
Hb Barts hyrops fetalis

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11
Q

Gene situ in alpha thalassaemia trait?

A

One or two genes missing

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12
Q

Gene situ in HbH disease ?

A

Only one alpha gene left

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13
Q

Gene situ in Hb Barts hydrops fetalis ?

A

No functional alpha genes

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14
Q

How do you distinguish alpha thalassaemia trait from iron deficiency?

A

Normal ferritin

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15
Q

What happens to the excess beta chains in HbH disease?

A

The form tetramers which cannot carry oxygen

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16
Q

Treatment of severe HbH disease?

A

Maybe need splenectomy +/- transfusion

17
Q

Can any HbA be made in Hb Barts hydrops fetalis?

A

No

18
Q

Beta thalassaemia is the result of what?

A

Disorder of beta chain synthesis

19
Q

What types of haemoglobin are affected in beta thalassaemia?

A

Only HbA as it is the only Hb that contains beta chains

20
Q

Which is the worst thalassaemia to have?

A

Alpha because it affects all types of haemoglobin - cannot substitute loss of HbA by making more of another

21
Q

When does beta thalassaemia major tend to present?

A

6-24 months old

22
Q

Why does beta thalassaemia major present at 6-24 months old?

A

Reduction in HbF so when trying to make HbA, realises there is a disorder in making the beta chains

23
Q

Haemoglobin analysis in beta thalassaemia major?

A

Mainly HbF

Minimal HbA

24
Q

Management of beta thalassaemia major?

A

Regular transfusion

Bone marrow transplant if be for complications develop

25
Q

Features of extramedullary haematopoiesis?

A

Hepatosplenomegaly
Skeletal changes
Organ damage

26
Q

Consequences of iron overload - endocrine

A

Impaired growth and pubertal development
Diabetes
Osteoporosis

27
Q

Consequences of iron overload - cardiac

A

Cardiomyopathy

Arrhythmias

28
Q

Consequences of iron overload - liver

A

Cirrhosis

Hepatocellular cancer

29
Q

Management of iron overload?

A

250mg of iron per unit of red cells

Iron chelating drugs - eg desferrioxamine

30
Q

How do iron chelating drugs manage iron overload?

A

Chelators bind to iron -> complexes form -> excreted in urine or stool

31
Q

What is the pathophysiology of sickling disorder?

A

Point mutation in codon 6 of beta globin gene - substitutes glutamine to valine -> Bs
Alters Hb -> HbS
HbS polymerises if exposed to low O2 -> distorts red cell, damaging RBC membrane

32
Q

Types of sickling disorder?

A 
Sickle trait (HbAS)
Sickle cell anaemia (HbSS)
33
Q

What happens in sickle cell trait?

A

One normal and one abnormal beta gene
Asymptomatic
Mainly HbA / <50% HbS

34
Q

What happens in sickle cell anaemia?

A 
Two abnormal beta genes 
No HbA
Sickle crisis 
Chronic haemolysis 
Hypospelnism due to repeated infarcts
35
Q

What happens in sickle crisis?

A

Sickle cell vaso-occlusion -> tissue ischaemia and sever pain

36
Q

Precipitants of sickle crisis?

A 
Hypoxia 
Dehydration 
Infection 
Cold exposure 
Stress/fatigue
37
Q

Treatment of sickle crisis?

A 
Opiate analgesia 
Hydration 
Rest 
Oxygen 
Antibiotics if evidence of infection 
Red cell exchange transfusion if severe
38
Q

Long term management of sickle crisis?

A

If hyposplenism- prophylactic penicillin and vaccinations to reduce risk of infection
Folic acid supplementation
Hydroxycarbamide can reduce severity of disease by inducing HbF production

Haematology (25 decks)

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