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Haematology > Haemaglobinopathies > Flashcards

Haemaglobinopathies Flashcards

1
Q

What are the three major forms of Haemoglobin?

A

HbA - 2 alpha 2 beta
HbA2 - 2 alpha 2 delta
HbF - 2 alpha 2 gamma

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2
Q

What form of Hb is the most common in adults?

A

HbA

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3
Q

What chromosome carries the gene for alpha chains?

A

C16

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4
Q

What chromosome carries the gene for beta chains?

A

c11

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5
Q

What are haemoglobinopathies?

A

Hereditary conditions affecting the globin chain synthesis

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6
Q

What are the two main groups of haemoglobinopathies?

A

Thalassaemia’s

Structure haemoglobin variants

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7
Q

What form of anaemia do thalassaemia’s cause?

A

Microcytic hypochromic anaemia

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8
Q

Why do thalassaemia’s lead to inadequate Hb production?

A

Unbalanced accumulation of globin chains (i.e. too many or too little of specific chains) means there is ineffective erythropoiesis and haemolysis

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9
Q

Mutations affecting the ___ chain production will lead to alpha thalassaemia:

A

Alpha chains

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10
Q

What is the name for alpha thalassaemia where only one or two genes are missing?
How would they present?

A

Alpha trait
Basically a carrier form. Patients tend to be asymptomatic and may have minor hematological changes e.g. low MCV and MCH
Ferritin will be normal

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11
Q

When 3 alpha genes are deleted it is called?

A

HbH disease

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12
Q

What findings are seen in HbH disease?

A

Severe form of the disease
Mild - moderate anaemia
Low MCV / MCH
Staining will show “golf ball” appearance

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13
Q

What is HbH

A

This is a tetrameter molecule formed with 4 beta chains.
These form due to the lack of alpha chains, meaning there is an excess in Beta chains.
This molecule is extremely unstable and cannot carry oxygen

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14
Q

Where in the world is HbH more prevalent?

A

S.E Asia
Middle East
Mediterranean

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15
Q

What clinical findings may be seen in a patietn with HbH

A

Symptoms of anaemia
Splenomegaly
Jaundice

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16
Q

How do you treat HbH

A

Most patients will require transfusions

May need splenectomy

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17
Q

Why is splenomegaly seen in HbH disease?

A

Extramedullary haematopoeisis occurs as a corrective measure

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18
Q

What is the name of the severest form of alpha thalassaemia?

A

Hb Barts Hydrops Fetalis Syndrome

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19
Q

What is Hb Barts Hydrops Fetalis Syndrome?

A

No alpha genes inherited from either parent
No alpha chains can be made - no functional Hb made
Most die in utero

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20
Q

What are the clinical features of Hb Barts Hydrops Fetalis Syndrome?

A 
Severe anaemia
Cardiac failure
Growth retardation
Severe hepatosplenomegaly
Skeletal and CV abnormalities
Usually die in utero
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21
Q

Beta thalassaemia is caused by a disorder with what?

A

Beta chain synthesis

22
Q

What causes Beta thalassaemia?

A

Point mutations leading to reduced or absent beta chain production

23
Q

What form of Hb is affected in Beta thalassaemia?

24
Q

What might be seen in a patient with B-thalassaemia trait?

A

Asymptomatic
No (mild anaemia)
Low MCH / MCV
Raised HbA2

25
What haemaglobinopathy is similar to HbH disease?
Beta thalassaemia intermedia
26
When will patients with beta thalassaemia intermedia require transfusions?
At times of additional physiological stress e.g. during inter current infections
27
When will beta thalassaemia major present?
Aged 6 - 24 months
28
What is the presenting symptoms/signs of beta thalassaemia major?
Pallor Failure to thrive Anaemia Signs of extramedullary erythropoeisis e.g. skeletal changes, organ damage and hepatosplenomegaly
29
What will be seen on a Hb analysis in beta thalassaemia major?
Hb is mainly HbF type | Minimal HbA will be seen
30
What is a serious complication of extramedullary erythropoeisis?
Spinal cord compression
31
How do you manage beta thalassaemia major?
Regular transfusions Monitor iron levels - avoid iron overload Bone marrow transplant
32
What range should Hb be kept in for beta thalassaemia major?
95-105 g/L
33
What are some consequences of iron overload?
``` Endocrine: - diabetes - osteoporosis - pubertal and growth delay Cardiac: - cardiomyopathy - arrhythmia Liver: - Cirrhosis - Hepatocellular cancer ```
34
What medication can be used to manage iron overload?
Iron Chelating drugs | e.g. desferrioxamine
35
How do Iron Chelating drugs work?
Chelators bind to iron and form complexes which can be excreted in the urine and stools
36
What is the consequence of the point mutation in sickling disorders?
Glutamine changes to valine producing BetaS | This forms the Hb structure HbS
37
What causes the HbS molecule to polymerize?
Exposure to low oxygen levels for a long time
38
What happens when HbS polymerizes?
The shape of the RBC membrane changes to form a sickle like shape
39
Sickle cell anaemia is an autosomal ______ disorder?
Recessive
40
What is a sickle crisis?
Vascular occlusion causing tissue infarction | EXTREMELY painful
41
Where are common areas for a sickle crisis to affect?
``` Digits bone marrow Lungs Spleen CNS ```
42
What are some other outcomes of sickle cell anaemia?
Chronic haemolysis due to shortened lifespan of RBC | Hyposplenism due to repeated infarcts
43
What are some precipitating risk factors of a sickle crisis?
``` Hypoxia Dehydration Infection Cold exposure Stress/fatigue ```
44
What is the management for a painful sickle crisis?
``` Opiate analgesia Hydration rest Oxygen therapy Antibiotics for infection Venesect and transfuse ```
45
What are some long term effects of sickle cell anaemia?
``` Growth impairment End organ damage Renal disease Pulmonary hypertension Avascular necrosis Leg ulcers Stroke ```
46
What is a consequence of hyposplenism and how is it managed?
Increased risk of infection Prophylaxis penicillin V Vaccinations - pneumococcus, pneumococcus and haemophilus
47
Why are sickle anaemia patients given folic acid supplements?
There is an increased RBC turnover rate, so there is an increased demand for folate
48
What drug is given to reduce severity of the disease and how does it work?
Hydroxycarbamide | induces HbF production
49
What blood test results will be seen in sickle cell anaemia?
Decreased Hb Increased Reticulocytes Increased Bilirubin
50
What will be seen on a blood film in sickle cell anaemia?
Target cells | Sickle cells
51
What is the diagnostic test for sickle cell anaemia?
Sickle solubility test confirms sickle cell anaemia | Hb electrophoresis confirms the type of Hb's present

Haematology (13 decks)

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