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Haematology > Iron and thalassaemia > Flashcards

Iron and thalassaemia Flashcards

1
Q

How many binding sites for iron does transferrin have?

A

2

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2
Q

% saturation of transferring measures what?

A

Measures iron supply.

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3
Q

What is the major negative regulator of iron?

A

Hepcidin.

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4
Q

What is the function of DMT-1

A

Transports iron into the duodenal enterocyte.

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5
Q

What is the role of ferroportin?

A

Facilitates iron export from the enterocyte.

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6
Q

What is the role of hepcidin?

A

To down regulate ferroportin in response to iron overload.

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7
Q

Skins changes in low iron? (2)

A

1) Koiloncychia.

2) Angular stomatitis

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8
Q

Anaemia of chronic disease e.g. iron malutilisation

A

Increased plasma hepcidin blocks ferroportin mediated release of iron.

Results in impaired iron supply to marrow erythroblastosis and eventually hypochromic red cells.

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9
Q

Iron overload with what amount of iron?

A

Usually with >5g

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10
Q

Clinical features of hereditary haemochromoatosis?

A 
Weakness/fatigue 
Joint pains 
Impotence. 
Arthritis 
Cirrhosis 
Diabetes 
Cardiomyopathy
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11
Q

Largest parenchymal store of iron?

Largest total iron store?

A

Liver = largest parenchymal store.

Haemoglobin = largest total store.

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12
Q

The causative mutations for haemochromoatosis are what?

A

C282Y

H63D

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13
Q

Management of haemochromoatosis?

A

Regular venesection is 1st line.

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14
Q

Typical presentation of haemochromatosis?

A

Typical patient is middle aged man.

Early: asymptomatic then fatigue, arthralgia, weakness.

Late: Slate grey skin, liver failure, diabetes&raquo_space; bronzed diabetes

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15
Q

What is defined as anaemia for an:

1) Adult male
2) Adult female non pregnant
3) Adult female pregnant

A

1) <130
2) <120
3) <110

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16
Q

At what level of Hb do you transfuse people?

A

<70

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17
Q

Treatment of hereditary haemochromoatosis?

A

Weekly phlebotomy (450-500ml)

Initial aim to exhaust iron stores (ferritin < 20ug/l)

Thereafter, keep ferritin below 50ug/l

Note: hereditary haemochromatosis may be asymptomatic until irreversible organ damage has occurred, this underlines the importance of family studies.

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18
Q

Causes of secondary iron overload?

A

Iron loading anaemias; repeated red cell transfusions (in thalassaemia and myelodysplastic syndromes)

Each unit of blood contains around 200-250mg iron, patients with thalassaemia required transfusion every 2-3 weeks.

Increased iron absorption can also cause an iron loading anaemia (over active erythropoiesis)

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19
Q

Treatment of secondary iron overload:

A

Venesection not usually an option in already anaemia patients

Therefore iron cheleasting agents are used:
- Desferrioxamine (SC or IV infusion)

New oral agents e.g. deferiprone are v expensive.

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20
Q

What is a thalassaemia?

A

A genetic defect of globin chain synthesis.

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21
Q

What is HbA composed of?

A

Alpha 2. Beta 2

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22
Q

What is HbA2 made of?

A

Alpha 2, delta 2

23
Q

What is HbF composed of?

A

Alpha 2 Gamma 2

24
Q

Where are alpha like genes located?

How many per chromosome?

A

Alpha genes occur on chromosome 16, Two alpha genes per chromosome (4 per cell)

25
Q

What chromosome are beta genes found on?

How many?

A

Beta genes are on chromosome 11, one beta per chromosome (2 per cell

26
Q

What are 2 main groups of haemoglobinopathies?

A

Thalassaemias (decreased rate of globin chain production)

Structural haemoglobin variants e.g. HbS

27
Q

Thalassaemias result in which type of anaemia?

A

Result in a hypochromic, microcytic anaemia

28
Q

In alpha thalassaemia, which types of haemoglobin will be affected?

A

All types due to alpha chains being present in all forms.

29
Q

Unaffected individuals have 4 normal a genes (aa/aa)

What does silent a thalassaemia trait look like?

A

Only one copy missing

(-a/aa). = clinically asymptomatic

30
Q

Alpha thalassaemia trait? Genotype and symptoms

A

Either (aa/—) or (a-/a-)

Clinically asymptomatic, Fbc will show a mild anaemia.

Red cell inclusions (Heinz bodies) (HbH bodies) can sometimes be seen with special stains.

31
Q

What is HbH disease?

A

Severe form of alpha thalassaemia, only one working alpha gene. (-a/- - )

Anaemia with very low MCV and MCH.

Due to globin chain imbalance, excess B tetramers form called HbH which cannot carry oxygen.

32
Q

How you diagnosis HbH disease (Alpha thalassaemia)

A

High performance liquid chromatography.

33
Q

Clinical features of HbH disease?

A

Splenomegaly due to extramedullary haemtopoesis.

Jaundice due to haemolytic and ineffective erythroporsis.

34
Q

Inheritance of HbH disease?

A

Behaves in an autosomal recessive fashion.

35
Q

Management of alpha thalassaemia?

A

Folic acid supplementation. (Aids erythropoesis)

Mild: intermittent transfusion

Severe: Regular transfusions.

36
Q

What is Hb Barr’s Hydrops Fetalis:

A

Severest form of alpha thalassaemia.

Occurs when patients have no alpha genes. Therefore, the only type of Hb that can be produced in Hb Barts.

Results in hydrops fetalois and uterine death.

37
Q

What is Hb Barts?

A

Gamma 4

38
Q

Diagnosis of alpha thalassaemia?

A

HPLC or haemoglobin electrophoresis.

39
Q

Note: molecular testing is needed to confirm alpha thal trait and determine the mutation involved. PCR used to screen for common mutations guided by patient’s ethnic background.

A

…

40
Q

Beta thalassaemias are usually caused by what?

How are they inherited?

A

Caused by point mutations.

Inherited in an autosomal recessive fashion.

41
Q

B+ means what

B(nought) means what?

A

B+ means reduced

Beta nought means absent .

42
Q

What is diagnostic for Beta thalassaemia trait?

A

A raised HbA2

43
Q

When does beta thalassaemia major occur?

A

Occurs when the patient is homozygous for Beta nought.

44
Q

When does beta thalassaemia present?

A

Usually presents in the first year of life with failure to thrive, severe anaemia.

Extramedullary haemotopoiesis (hepatoslpenogaly, frontal bossing, multiple organ damage)

45
Q

What does the Skull XR show in beta thal major?

A

Hair on end sign.

46
Q

Lab features of B thal major?

A

Moderate to severe anaemia (Hb 30-90)
Reticulocytosis
Film shows: anispoikilocytosis and target cells

HPLC shows mainly HbF present, small amount of HbA and HbA2 often elevated.

47
Q

Management of B thal major?

A

Life long transfusion.
Folate supplentation.

THe main mortality is from iron overload from loads of transfusions.

48
Q

How is sickle cell anaemia inherited?

A

Autosomal recessive.

49
Q

What is the pathophysiology of Sickle Cell anaemia?

A

A point mutation in codon 6 of the Beta globin gene that substitutes glutamine to valine (denoted Beta(s)

This alters the structure of Hb to HBS (alpha 2, Beta(s)2)

50
Q

What happens to HbS if it is exposed to low oxygen?

A

It polymerises, the distorts the red cell damaging the cell membrane.

51
Q

Sickle cell trait = one abnormal beta gene., features?

A

May sickle in severe hypoxia e.g. high altitude, under anaesthesia.

Few clinical features as HbS levels too low to polymerise.

Blood film normal or mild drop in MCV/MCH.

52
Q

What does MCH stand for?

A

Mean Corpuscular Haemoglobin.

Normal value - normochromic.
Low value = hypochromic.

53
Q

Treatment of painful crisis in sickle cell disease?

A 
Opiate analgesia. 
Hydration 
Rest 
Oxygen 
Antibiotics if evidence of infection. 
Red cell exchange transfusion in severe crisis e.g. chest or neuro crisis.
54
Q

What can be used in sickle cell disease to reduce the severity of disease by inducing HbF production?

A

Hydroxycarbamide.

Haematology (12 decks)

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