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Haematology > Haemoglobinopathies > Flashcards

Haemoglobinopathies Flashcards

1
Q

What are haemoglobinopathies?

A

Disorders of globin - there is no issue with haem.

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2
Q

What are the 3 types of haemoglobin?

A

HbA (2 alpha and 2 beta)
HbA2 (2 alpha and 2 delta)
HbF (2 alpha and 2 gamma)

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3
Q

How many alpha genes are there in each cell?

A

There are 4 of these per cell - 2 found on each chromosome.

Will be found on chromosome 16.

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4
Q

Which chromosome are the beta genes found on?

A

Chromosome 11

Only 2 genes are found per cell.

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5
Q

What pattern of inheritance is typically seen in haemoglobinopathies?

A

Autosomal recessive

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6
Q

How long does it take from birth for beta chains to begin production?

A

6-12 months.

Will produce Hbf before this point.

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7
Q

What is the problem in thalassaemias?

A

There is a decreased rate of globin synthesis.

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8
Q

What form of anaemia is caused by thalassaemia?

A

Microcytic hypochromic anaemia

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9
Q

What is alpha thalassaemia trait?

A

When there is 1 or 2 missing alpha genes (out of the 4 total).

Patient will be asymptomatic or only suffer from mild anaemic symptoms.

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10
Q

What is HbH disease?

A

When 3 alpha genes are missing - only one remains.

This is the most severe form of alpha thalassaemia that is compatible with life.

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11
Q

What is Hb Barts hydrops fetalis?

A

The absence of any functional alpha genes.

This is incompatible with life.

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12
Q

What is beta thalassaemia?

A

A disorder of beta chain synthesis.

This is caused by point mutations.

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13
Q

What type of mutation brings about alpha thalassaemia?

A

A deletion

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14
Q

What is the only form of haemoglobin affected by beta thalassaemia?

A

HbA

This is due to B-globins only being involved in this form of haemoglobin.

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15
Q

What is beta thalassaemia trait?

A

An asymptomatic carrier state that may only cause mild anaemia.

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16
Q

How is beta thalassaemia trait diagnosed?

A

Perform blood testing to detect raised HbA2 levels within the blood.

17
Q

What is beta thalassaemia intermedia?

A

A moderate severity disorder that requires occasional transfusions.

18
Q

What is beta thalassaemia major?

A

A severe condition, with patients requiring lifelong transfusions.

19
Q

What should be ruled out in alpha thalassaemia trait?

A

Iron deficiency

Achieved by measuring ferritin levels (these are normal in alpha thalassaemia trait but low in iron-deficiency).

20
Q

How are beta globins found in those with HbH disease?

A

Within abnormal tetramers, called HbH.

21
Q

How long does it take for beta thalassaemia major to present?

A

6-12 months - as the body attempts to switch to HbA production.

Will cause progressive anaemia, pallor and a failure to thrive.

22
Q

What is ‘frontal bossing’ characteristic of?

A

Extramedullary haematopoiesis

Seen as body attempts to compensate for an anaemia.

23
Q

How is beta thalassaemia major treated?

A

Life-long transfusion.

Aim to maintain Hb between 95-105g/L.

24
Q

What is a complication of regular transfusions?

A

Iron overload

Main cause of death in beta thalassaemia major.

25
Q

How is iron overload treated?

A

Iron chelating agents.

These bind to iron, aiding its secretion.

26
Q

Why is venesection not appropriate in beta thalassaemia major?

A

As these patients are already anaemic, meaning this would only make the problem at hand worse.

27
Q

What are sickle cell disorders?

A

Disorders caused by point mutation of the beta globulin gene, resulting in production of HbS

28
Q

What is the consequence of HbS?

A

These RBCs are stickier, meaning they can adhere to vascular endothelium more easily.

29
Q

What is sickle cell trait?

A

The presence of an affected gene and an unaffected gene.

Essentially asymptomatic - features only present in severe hypoxia.

HbS will be seen on blood film.

30
Q

What is sickle cell anaemia?

A

A condition caused by the inheritance of 2 abnormal genes, meaning only HbS is produced - patient has no HbA.

31
Q

What is a sickle cell crisis?

A

Episodic tissue infarction caused by microvascular occlusion.

Patient will present with very severe pain.

32
Q

What factors can precipitate a sickle cell crisis?

A

Hypoxia
Dehydration
Infection
Stress/Fatigue

33
Q

How is sickle cell crisis treated?

A

Opiate analgesia (e.g. IV/SC morphine)
Hydration
Oxygen
Rest

Treat infection if present.

34
Q

What is carried out if patient has severe sickle cell crisis affecting a major organ?

A

Red cell exchange transfusion.

35
Q

Why is hydroxycarbimide given in sickle cell anaemia?

A

To induce HbF production.

36
Q

What prophylactic steps should be taken in sickle cell anaemia?

A

Vaccinations
Prophylactic penicillin
Folic acid supplements

Haematology (20 decks)

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