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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?

A

HbA

24
Q

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

A

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

25
Q

What haemaglobinopathy is similar to HbH disease?

A

Beta thalassaemia intermedia

26
Q

When will patients with beta thalassaemia intermedia require transfusions?

A

At times of additional physiological stress e.g. during inter current infections

27
Q

When will beta thalassaemia major present?

A

Aged 6 - 24 months

28
Q

What is the presenting symptoms/signs of beta thalassaemia major?

A

Pallor
Failure to thrive
Anaemia
Signs of extramedullary erythropoeisis e.g. skeletal changes, organ damage and hepatosplenomegaly

29
Q

What will be seen on a Hb analysis in beta thalassaemia major?

A

Hb is mainly HbF type

Minimal HbA will be seen

30
Q

What is a serious complication of extramedullary erythropoeisis?

A

Spinal cord compression

31
Q

How do you manage beta thalassaemia major?

A

Regular transfusions
Monitor iron levels - avoid iron overload
Bone marrow transplant

32
Q

What range should Hb be kept in for beta thalassaemia major?

A

95-105 g/L

33
Q

What are some consequences of iron overload?

A 
Endocrine: 
 - diabetes
 - osteoporosis
 - pubertal and growth delay
Cardiac:
 - cardiomyopathy
 - arrhythmia
Liver:
 - Cirrhosis
 - Hepatocellular cancer
34
Q

What medication can be used to manage iron overload?

A

Iron Chelating drugs

e.g. desferrioxamine

35
Q

How do Iron Chelating drugs work?

A

Chelators bind to iron and form complexes which can be excreted in the urine and stools

36
Q

What is the consequence of the point mutation in sickling disorders?

A

Glutamine changes to valine producing BetaS

This forms the Hb structure HbS

37
Q

What causes the HbS molecule to polymerize?

A

Exposure to low oxygen levels for a long time

38
Q

What happens when HbS polymerizes?

A

The shape of the RBC membrane changes to form a sickle like shape

39
Q

Sickle cell anaemia is an autosomal ______ disorder?

A

Recessive

40
Q

What is a sickle crisis?

A

Vascular occlusion causing tissue infarction

EXTREMELY painful

41
Q

Where are common areas for a sickle crisis to affect?

A 
Digits
bone marrow
Lungs
Spleen
CNS
42
Q

What are some other outcomes of sickle cell anaemia?

A

Chronic haemolysis due to shortened lifespan of RBC

Hyposplenism due to repeated infarcts

43
Q

What are some precipitating risk factors of a sickle crisis?

A 
Hypoxia
Dehydration
Infection
Cold exposure
Stress/fatigue
44
Q

What is the management for a painful sickle crisis?

A 
Opiate analgesia
Hydration
rest
Oxygen therapy
Antibiotics for infection
Venesect and transfuse
45
Q

What are some long term effects of sickle cell anaemia?

A 
Growth impairment 
End organ damage
Renal disease
Pulmonary hypertension
Avascular necrosis
Leg ulcers
Stroke
46
Q

What is a consequence of hyposplenism and how is it managed?

A

Increased risk of infection
Prophylaxis penicillin V
Vaccinations - pneumococcus, pneumococcus and haemophilus

47
Q

Why are sickle anaemia patients given folic acid supplements?

A

There is an increased RBC turnover rate, so there is an increased demand for folate

48
Q

What drug is given to reduce severity of the disease and how does it work?

A

Hydroxycarbamide

induces HbF production

49
Q

What blood test results will be seen in sickle cell anaemia?

A

Decreased Hb
Increased Reticulocytes
Increased Bilirubin

50
Q

What will be seen on a blood film in sickle cell anaemia?

A

Target cells

Sickle cells

51
Q

What is the diagnostic test for sickle cell anaemia?

A

Sickle solubility test confirms sickle cell anaemia

Hb electrophoresis confirms the type of Hb’s present

Haematology (13 decks)

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