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3MB Haematology > Thalassaemia & SCA > Flashcards

Thalassaemia & SCA Flashcards

1
Q

Define Thalassaemia

A

Genetic defect in the protein chains that make up haemoglobin

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2
Q

Defects in alpha-globin chains lead to..

A

Alpha thalassaemia

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3
Q

Defects in the beta-globin chains lead to..

A

Beta thalassaemia

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4
Q

Both thalassaemia conditions are autosomal dominant/ recessive

A

Recessive

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5
Q

Explain the pathophysiology of thalassaemia

A

The RBCs are more fragile and break down easily, causing haemolytic anaemia. The spleen acts as a sieve, filtering the blood and removing older cells, it collects all the destroyed red blood cells, resulting in splenomegaly

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6
Q

Microcytic anaemia (low mean corpuscular volume)

A

Thalassaemia

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7
Q

Raised ferritin on Thalassaemia suggests..

A

Iron overload

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8
Q

Ix for Thalassaemia

A

FBC
Haemoglobin electrophoresis for globin abnormalities
DNA testing for genetic abnormality

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9
Q

Iron overload may occur in thalassaemia due to..

A

Increased iron absorption in the gastrointestinal tract
Blood transfusions

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10
Q

Iron overload in thalassaemia can cause symptoms and complications of..

A

Liver cirrhosis
Hypogonadism
Hypothyroidism
Heart failure
Diabetes
Osteoporosis

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11
Q

For iron overload, serum _____ levels are monitored. Management involves __________ and __________

A

For iron overload, serum ferritin levels are monitored. Management involves limiting transfusions and iron chelation

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12
Q

The genes that code for alpha-globin are found on chromosome..

A

16

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13
Q

The severity of symptoms in thalassaemia varies depending on the type and number of genetic defects. What are these?

A

Carrier
Moderate anaemia (haemoglobin H disease)
Intrauterine death due to severe fetal anaemia (alpha thalassemia major)

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14
Q

Mx for alpha thalassaemia

A

Monitoring
Blood transfusions
Splenectomy may be performed
Bone marrow transplant can be curative

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15
Q

If 1 or 2 alpha globulin alleles in alpha-thalassaemia are affected then the blood picture would be…

A

Hypochromic and microcytic, but the Hb level would be typically normal

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16
Q

If there are 3 alpha globulin alleles affected in alpha-thalassaemia it results in..

A

Hypochromic microcytic anaemia with splenomegaly. This is known as Hb H disease

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17
Q

f all 4 alpha globulin alleles are affected in alpha-thalassaemia (i.e. homozygote) then it results in..

A

Death in utero (hydrops fetalis, Bart’s hydrops)

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18
Q

The gene coding for protein chains in beta-thalassaemia is on chromosome..

A

11

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19
Q

In beta-thalassaemia, the gene defects can either consist of..

A

Abnormal copies that retain some function or deletion genes with no function in the beta-globin

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20
Q

Beta-thalassaemia can be split into three types..

A

Thalassaemia minor
Thalassaemia intermedia
Thalassaemia major

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21
Q

What is Thalassaemia Minor?

A

Carriers of an abnormally functioning beta-globin gene. They have one abnormal and one normal gene. Causes mild microcytic anaemia and usually only requires monitoring

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22
Q

What is Thalassaemia Intermedia?

A

Two abnormal copies of the beta-globin gene. This can be either:

Two defective genes
One defective gene and one deletion gene

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23
Q

Mx for Thalassaemia Intermedia

A

Significant microcytic anaemia so require monitoring and may need occasional blood transfusions. May require iron chelation to prevent iron overload

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24
Q

What is Thalassaemia Major?

A

Most severe form. Homozygous for the deletion genes. They have no functioning beta-globin genes

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25
Q

Why does Thalassaemia Major causes fractures?

A

The bone marrow is under so much strain to produce extra red blood cells to compensate for the chronic anaemia that it expands enough to increase the risk of fractures and change the patient’s appearance

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26
Q

Abnormal features relating to bone changes in Thalassaemia Major include..

A

Frontal bossing (prominent forehead)
Enlarged maxilla (prominent cheekbones)
Depressed nasal bridge (flat nose)
Protruding upper teeth

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27
Q

Mx for Thalassaemia Major

A

Repeated transfusions and splenectomy. A bone marrow transplant can be curative

Transfusion can lead to iron overload → organ failure. So iron chelation therapy is important (e.g. desferrioxamine)

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28
Q

Mild hypochromic, microcytic anaemia. It is usually asymptomatic
HbA2 raised (> 3.5%)

A

Beta thalassaemia trait

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29
Q

What is sickle cell anaemia?

A

Genetic condition that causes sickle (crescent) shaped red blood cells. This makes it more fragile and easily destroyed leading to haemolytic anaemia

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30
Q

Patients with sickle cell anaemia are prone to..

A

Various sickle cell crises

31
Q

Patients with sickle-cell disease have an abnormal variant called..

A

Haemoglobin S (HbS)

32
Q

Sickle cell disease is more common in patients from areas traditionally affected by..

A

Malaria, such as Africa, India, the Middle East and the Caribbean

33
Q

T or F: Having one copy of the gene (sickle cell trait) reduces the severity of malaria

A

True - patients with sickle cell trait are more likely to survive malaria and pass on their genes. Therefore, there is a selective advantage to having the sickle cell gene in areas of malaria, making it more common.

34
Q

Screening for Sca

A

Newborn blood spot screening test at around five days of age

Pregnant women at high risk of being carriers of the sickle cell gene are offered testing

35
Q

What is Sickle cell crisis?

A

Spectrum of acute exacerbations caused by sickle cell disease. These range from mild to life-threatening. They can occur spontaneously or triggered by dehydration, infection, stress or cold weather

36
Q

Symptoms in homozygotes SCA don’t tend to develop until..

A

4-6 months when the abnormal HbSS molecules take over from fetal haemoglobin

37
Q

Some patients inherit one HbS and another abnormal haemoglobin (HbC) resulting in..

A

Milder form of sickle cell disease (HbSC)

38
Q

Pathophysiology of SCA

A

Polar amino acid glutamate is substituted by non-polar valine in each of the two beta chains (codon 6). This decreases the water solubility of deoxy-Hb

In the deoxygenated state the HbS molecules polymerise and cause RBCs to sickle

39
Q

Definitive diagnosis of sickle cell disease is by..

A

Haemoglobin electrophoresis

40
Q

Long term mx for SCA

A

Hydroxyurea - increases the HbF levels and is used in the prophylactic management of sickle cell anaemia to prevent painful episodes

Sickle cell patients should receive the pneumococcal polysaccharide vaccine every 5 years

41
Q

Type of sickle cell crises

A

Thrombotic, ‘vaso-occlusive’, ‘painful crises’
Acute chest syndrome
Anaemic - aplastic, sequestration
Infection

42
Q

What causes thrombotic crises?

A

Infection, dehydration, deoxygenation (e.g. high altitude)

43
Q

Ix for thrombotic crises

A

Diagnosed clinically

44
Q

What is acute chest syndrome?

A

Vaso-occlusion within the pulmonary microvasculature → infarction in the lung parenchyma

45
Q

Dyspnoea, chest pain, pulmonary infiltrates on chest x-ray, low pO2

A

Acute chest syndrome

46
Q

Mx of acute chest syndrome

A

Pain relief
Respiratory support e.g. oxygen therapy
Antibiotics: infection may precipitate acute chest syndrome and the clinical findings (respiratory symptoms with pulmonary infiltrates) can be difficult to distinguish from pneumonia
Transfusion: improves oxygenation

47
Q

The most common cause of death after childhood

A

Acute chest syndrome

48
Q

What causes aplastic crises?

A

Caused by infection with parvovirus

49
Q

Sudden fall in haemoglobin

A

Aplastic crises

50
Q

In an aplastic crises, ______________ causes a reduced reticulocyte count

A

Bone marrow suppression

51
Q

What is Sequestration crises?

A

Sickling within organs such as the spleen or lungs causes pooling of blood with worsening of the anaemia

52
Q

Sequestration crises is associated with a decreased/increased reticulocyte count

A

Increased

53
Q

Mx for sickle-cell crises

A

Analgesia e.g. opiates
Rehydrate
Oxygen
Consider antibiotics if evidence of infection
Blood transfusion

54
Q

When is exchange transfusion indicated in sickle cell crises?

A

Acute vaso-occlusive crisis (stroke, acute chest syndrome, multiorgan failure, splenic sequestration crisis)

It rapidly reduce the percentage of Hb S containing cells

55
Q

When is blood perfusion indicated in sickle cell crises?

A

Severe or symptomatic anaemia, pregnancy, pre-operative

Do not rapidly reduce the percentage of Hb S containing cells
exchange transfusion

56
Q

Pain and swelling in the hands or feet but can affect the chest, back, or other body areas. It can be associated with fever

It can cause priapism in men by trapping blood in the penis, causing a painful and persistent erection

A

Vaso-occlusive Crisis

57
Q

Hypovolaemic shock occurs secondary to which type of SCA crises?

A

Splenic Sequestration Crisis

58
Q

A vaso-occlusive crisis, fat embolism or infection can trigger..

A

Acute Chest Syndrome

59
Q

Which medications are used in Acute Chest Syndrome?

A

Hydroxycarbamide (stimulates HbF)
Crizanlizumab (targets P-selectin)

60
Q

T or F: In alpha thalassaemia, α chains are present in HbA, HbA2
and HbF therefore all are affected

A

True

61
Q

Excess β chains form tetramers (β4) called..

A

HbH

62
Q

One or two alpha genes missing

A

α thalassaemia trait

63
Q

Only one alpha gene left

A

HbH disease

64
Q

No functional α genes

A

Hb Barts hydrops fetalis

65
Q

β+/β or β0/β

A

β thalassaemia trait

66
Q

β+/β+ or β0/β+

A

β thalassaemia intermedia

67
Q

β0/β0

A

β thalassaemia major

68
Q

β thalassaemia major leads to Extramedullary haematopoiesis which can cause..

A

Cord compression

69
Q

Mx of iron overload

A

Iron chelating drugs (eg desferrioxamine)

70
Q

Hb→ HbS (α2βs2)

A

Sickling disorder

71
Q

β/βs

A

Sick cell trait

72
Q

βs/βs

A

SCA

73
Q

Chronic haemolysis + hyposplenism

A

SCA

3MB Haematology (23 decks)

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