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Sickle Cell and Haemoglobinopathies Flashcards

1
Q

What is normal Hb?

A

HbA

Adult haemoglobin

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2
Q

What is adult Hb made up of?

A

4 globin chains

  • 2 alpha
  • 2 beta

4 haem molecules, one bound to each chain

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3
Q

Define haemoglobinopathies

A

Structural Abnormalities affecting globin chains in Hb molecules

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4
Q

Example of haemoglobinopathy

A

Sickle cell disease

Presence of HbS in beta chain due to mutation

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5
Q

Causes of thalassaemia?

A
  • reduced/absent production of beta or alpha chain = ineffective erythropoiesis
  • effects of anaemia
  • effects of iron overload in transfused patients
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6
Q

Cause of sickle cell

A

HbS

Glutamate substituted by valine in position 6 of beta gene

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7
Q

Inheritance of sickle cell

A
  • autosomal recessive
  • mendelian mode of inheritance
  • carries = asymptomatic
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8
Q

Pathophys of sickle cell

A
  • polymerisation = sickling
  • this results in vaso-occlusion/infarction AND haemolysis
  • precipitated by hypoxia, HbS conc/dehydration, acidosis
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9
Q

Clinical diagnosis of sickle cell

A

FH

Recurrent pain

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10
Q

Lab diagnosis of sickle cell

A
  • anaemia
  • haemolysis (high bilirubin, high LDH, raised reticulocytes, undetectable haptoglobin)
  • blood film
  • haemoglobin electrophoresis/sickle solubility test
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11
Q

Sickle solubility test

A
  • negative = can see lines behind tube

- positive = cannot see lines behind tube

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12
Q

Emergency presentations/complications of sickle cell

A

1) pain/acute painful crisis
2) splenic sequestration
3) aplastic crisis
4) overwhelming sepsis
5) acute chest syndrome
6) fat embolism syndrome/mutli organ failure
7) priapism (splenic sequestration mechanism)
8) acute infarct

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13
Q

What can an acute infarct cause?

A

Stroke
MI
Acute visual loss
Acute renal failure

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14
Q

Presentation of painful sickle cell crisis

A
  • rapid onset
  • bone pain
  • bone marrow infarction
  • hours-weeks variable
  • fever, bone tenderness, swelling, hypertension, tachycardic, tachypnoea
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15
Q

Precipitating factors of painful sickle cell crisis

A
  • infections
  • skin cooling
  • dehydration
  • deoxygenation
  • stress
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16
Q

Analgesia procedures for sickle cell crisis

A
  • within 30min of presentation
  • parenteral opiates
  • re-assess and repeat as necessary
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17
Q

What to monitor in sickle cell crisis?

A
  • vital signs
  • temp
  • fluid intake
  • analgesia use and pain score
  • sedation/urinary retention/restlessness
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18
Q

Investigations in sickle cell crisis

A
  • FBC and reticulocytes
  • U&E/LFT
  • LDH
  • CRP
  • Blood cultures
  • CXR
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19
Q

What is acute chest syndrome?

A
  • acute illness
  • new infiltrate on CXR
  • respiratory syndromes
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20
Q

Triggers of acute chest syndrome

A
  • surgery/anesthesia
  • pregnancy
  • increased risk of chronic lung disease
  • increased risk of death
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21
Q

Sickle cell positive feedback symptoms

A

hypoxi, inflammation and acidosis = vaso-occlusion within pulmonary microvasculature = fat embolism and pulmonary thrombi

BUT vaso-occlusion causes more hypoxia/inflammation/acidosis

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22
Q

Management of sickle cell crisis

A
  • analgesia
  • incentive spirometry = reduces ACS
  • O2 therapy
  • fluids
  • AB
  • transfusion
23
Q

Which transfusion to give in sickle cell crisis

A
  • TUT = mild ACS

- ExTx gen = moderate/severe ACS

24
Q

Overwhelming hyposplenic sepsis cause

A

Pneumococcal
Meningococcal
Haemophilus influenzae

25
Overwhelming hyposplenic sepsis symptoms
Febrile Coma Altered sensorium Seizures
26
Overwhelming Hyposplenic sepsis treatment
Urgent AB treatment Prophylactic Pen V Vaccination
27
Overwhelming Hyposplenic sepsis who?
<3 years | splenic auto-infarction from very young age = functional asplenia
28
Sequestration define
- acute deterioration of anaemia - painful enlargement of spleen - drop in Hb>2g/L
29
Sequestration who?
- children | - <2years
30
Sequestration management
- early detection - parental education - urgent blood transfusion - splenectomy
31
Sequestration prognosis
- recurrence = 50% | - mortality = 12%
32
Aplastic crisis cause
infection with HPV B19 - infection of red cell precursors in bone marrow = pure red cell aplasia = low reticulocytes - Hb nadir 15 days post infection
33
Aplastic crisis who
- childhood illness common | - slapped cheek disease
34
Aplastic crisis management
Urgent blood treatment
35
Inheritance of thalassaemia
- autosomal recessive - mutations = deletion of alpha globin or beta globin genes - carries asymptomatic = thalassaemia minors
36
What anaemia do you get with thalassaemia?
microcytic hypochromic | with haemolysis
37
Beta thalassaemia major define
- deletion of beta globin gene - lack of production of beta chains - homozygous
38
How to treat beta thalassaemia major?
- transfusion dependent | - get secondary iron overload
39
Clinical features of beta thalassaemia major?
- severe anaemia - growth failure - HF as high output - bone marrow expansion - death in 1st and 2nd decade without transfusion - regular transfusions from early to maintain Hb>10
40
Consequences of bone marrow expansion in beta thalassaemia major?
- thalassaemic facies - poor dentition - interdental separation - hair on end appearance on skull x-ray - bone disease - extramedullary haemopoiesis
41
Haemosiderosis
- tranfusional iron overall - without chelation - effects appear by end of first decade
42
Clinical features of iron overload
- impaired growth - infertility - hypoparathyroidism - cardiomyopathy - cardiac failure - hepatic cirrhosis - diabetes mellitus - hypogonadism - sudden arrhythmia = death in teens/early 20s
43
How to assess iron status?
- liver biopsy (invasive) - serum ferritin (non specific) - cardiac/liver MRI
44
Gold standard to assess iron status for iron overload
cardiac/liver MRI
45
Iron chelating agents
- desferoxamine (continuous infusion) - deferiprone (oral) - deferassirox (oral) - combination
46
Which thalassaemia is worse
Beta worse than alpha
47
Alpha thalassaemia prevalent areas
China SE Asia Eastern Mediterranean Middle East
48
Inheritance of alpha thalassaemia
2 sets of genes located on chromosome 16 | 2 inherited from each parent
49
Alpha thalassaemia minor
- asymptomtic - mild microcytic anaemia - 2 from 1 parent or 1 from both
50
Hb H disease
- symptomatic - haemolytic and microcytic anaemia - splenomegaly - 3, 2 from 1 parent, 1 from other
51
Alpha thalassaemia major
- 2 from each parents - incompatible with life - hydrops fetalis
52
Thalassaemia Intermedia
- anaemia - not transfusion dependent - risk of iron overload as increased absorption - Beta thalssaemia major with alpha thalassaemia trait - beta thalssaemia trait with triplicate alpha chains - e.g. delta-beta thalassaemia - e.g. HbE beta thalassaemia
53
Antenatal Screening
Heel Prick test - identify all pregnancies with haemoglobinopathy risk - offer partner screening - genetic counselling to affected
54
Children at birth with sickle cell management?
- pencillin prophylaxis - immunisation - parent education

CR3 (30 decks)

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