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CR2 > 33 - Haemoglobinopathies > Flashcards

33 - Haemoglobinopathies Flashcards

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1
Q

What is adult haemoglobin

A

2 alpha
2 beta
(Haemoglobin A)

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2
Q

How many genes are there for the alpha subunit

A

2
(4 genes in a normal diploid)
also a zeta gene

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3
Q

What chromosome is the alpha subunit on

A

16

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4
Q

How many genes are there for the beta subunit and what are they called

A

5

Epsilon, gamma A, gamma G, delta and beta

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5
Q

Where is the first form of hb made

A

Embryonic sac

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6
Q

What is the 1st form of hb called and what is it made up of

A

Hb Gower 1
Zeta x2
Epsilon X2

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7
Q

What other variants of Hb can occur in the early weeks

A

Gower 2 - A2E2

Portland - Z2E2

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8
Q

What is the form of Hb that is produced after 6 weeks and what is it made up of

A

Fetal haemoglobin F
HbG
Alpha x2
Gamma x2

This replaces Hb Gower 1

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9
Q

Where is HbG produced

A

Liver and spleen

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10
Q

After 3-6months of birth what replaces HbG

A

HbA

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11
Q

What is thalassemia

A

Genetic defect resulting in inadequate quantities of one or other of the subunits that make up haemoglobin

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12
Q

What is alpha thalassemia

A

one or more of the alpha genes on chromosome 16 is deleted/faulty

Manifested at birth
Severity depends on no of genes alleles that are defective

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13
Q

One alpha gene defective

A

Alpha thalassemia minima
Minimal effect on Hb synthesis
No clinical symptoms
Slightly reduced MCV and MCHb

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14
Q

Two alpha genes defective

A

Alpha thalassemia Minor

Mild microcytic hypochromatic anaemia

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15
Q

Three alpha genes defective

A

Haemoglobin H disease
2 unstable Hb in blood
Microcytic hypochromatic anaemia
Higher affinity for oxygen so poor release of O2 in tissues

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16
Q

What are the 2 abnormal hb in haemoglobin H disease

A

Hb Barts - G4

Hb H - B4

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17
Q

Four alpha genes defective

A

Fetus cannot live outside the uterus - stillborn
Hydrops fetalis
Little circulating Hb

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18
Q

What is the Hb that is present in thalassemia with 4 alpha genes defective

A

Hb Barts - tetrameric y chain (gamma)

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19
Q

What is beta thalassemia

A

a point mutation on chromosome 11 in Hb B gene

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20
Q

What inheritance is B thalassemia

A

Autosomal recessive inheritance

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21
Q

What is the difference between heterozygous and homozygous thalassemia

Study These Flashcards
A

Beta thalassemia minor

Beta thalassemia major (B0 Cooley’s anaemia)

22
Q

Beta thalassemia intermedia

Study These Flashcards
A

Both beta globin genes are mutated but the body can make some

23
Q

When does B thalassemia manifest

Study These Flashcards
A

When switch from gamma to beta chain after birth

may be compensatory but you get an increase in HbF and A2

24
Q

What are the pathological effects of B thalassemia

Study These Flashcards
A

Excess alpha globins (unstable) which precipitate on erythrocyte membrane
This causes intramedullary destruction of erythroblasts

= SEVERE HYPOCHROMATIC MICROCYTIC ANAEMIA

25
What are untreated effects of B thalassemia major
- Hypochromatic, microcytic anaemia - Bone marrow expansion, splenomegaly - Bone deformity, extramedullary erythropoeitic masses - Failure to thrive from 6 months of age - Pallor, short stature, facial bone abnormalities
26
What are causes of B thalassemia
Mutation in non-coding introns deletion of globin gene mutation in promotor, nonsense mutation
27
Treatment of thalassemia major
Regular transfusions Iron chelation therapy Splenectomy Allogenic bone transplant
28
Why do you need iron chelation therapy
The regular transfusions can cause iron overload
29
How do you distinguish iron deficiency anaemia from thalassaemia
Thalassemia has normal serum iron and ferritin
30
Why is excess iron a bad thing?
Causes excess haemolysis | Free iron can be released into the blood from haem
31
What is the fenton reaction
If hydrogen peroxide is present the fenton reaction occurs hydroxyl radicals are produced = Oxidise and damage biological tissues
32
What diseases are fenton reaction responsible for
Cirrhosis Diabetes glandular dysfunction
33
What do iron chelating compounds do
Bind free iron and prevent the fenton reaction
34
What are some examples of iron chelation therapies
Desferoxamine (desferal) Deferiprone, Ferriprox Desferasirox, exjade
35
Desferoxamine (desferal)
Chelation enhanced with ascorbate | Toxicity with higher doses
36
Deferiprone, Ferriprox
Oral iron chelator | Not to be used in pregnancy
37
Deferasirox, Exjade
A once daily oral iron chelator | Can cause GI bleeding and kidney or liver failure
38
What is sickle cell disease
Mutant form of Beta haemoglobin subunits -red cells to become sickle shaped
39
Why are sickle shaped RBC not good
Obstruct capillaries and restrict blood flow | Causes ischemic pain and organ damage
40
What are signs of SCD
Haemolytic anaemia: haemoglobin levels in the range of 6–8 g/dL (usually 12 -17) Large vessel damage Microvascular occlusion
41
What is the mutation in sickle hb (HbS)
Glutamic aid to valine (GAG-GTG) | Substitution at codon 6 of the B globin chain
42
What is Haemoglobin S made up of
``` Alpha 2 Bs 2 (abnormal B chain) ```
43
When does HbS distort the RBC to sickle shape
When the blood is deoxygenated
44
Clinical consequences of SCD
Anaemia Increased susceptibility to infection Vaso-occlusive crises Chronic tissues damage
45
Management of SCD
``` Infection prophylaxis Analgesics for painful crises Education, lifestyle Transfusions Bone marrow transplants ```
46
Screening
Blood screen | genetic councelling
47
Neonatal
Treat with antibiotic prophylaxis Education Heel-prick sample
48
Haemoglobin C
Abnormal B sub unit Reduced plasticity and flexibility of the erythrocytes (excess haemolysis) Hb C disease
49
Haemoglobin E
``` Abnormal Hb with single point mutation in the B chain Inherited from both parents Mild B-thalassemia symptoms after 3-6 months Mild splenomegaly ```
50
Haemoglobin A2
Minor component of Hb Found in RBC after birth (3%) 2A 2Delta
51
Glucose-6-phosphate dehydrogenase deficiency (G6PD deficiency)
``` X-linked recessive error of metabolism Haemolysis and jaundice in response to triggers Broad beans and oxidative drugs Mediterranean - common protected from malaria ```

CR2 (34 decks)

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