Condition- SCD

Question 1

At what age does sickle cell anaemia tend to present and why?

Answer 1

3-6 months, when gamma globin production is switched off and Beta globin is switched on

Question 2

Describe the inheritance of SCD

Answer 2

Autosomal Recessive

Question 3

Describe the genetics of sickle cell disease, sickle cell trait and sickle cell anaemia

Answer 3

• Sickle Cell Anaemia = HbSS
• Sickle Cell Trait = HbSA
• Sickle Cell Disease = HbSC or HbS/Bthal (HbS with other B-globinopathies)

Question 4

Which mutation causes Sickle cell disease? (type of mutation and which chromosome and gene?)

Answer 4

Point mutation, codon 6 on the Beta-globin gene of Chr11

Question 5

The point mutation causing sickle cell disease causes what amino acid substition?

Answer 5

Glutamic Acid (polar) => Valine (non-polar)

Question 6

Sickle Cell trait provides protection against which disease?

Answer 6

Plasmodium Falciparum Malaria

Question 7

What causes the sickling of RBCs in SCD?

Answer 7

• Deoxygenation of HbS causes it to change shape
• This leads to polymerisation of multiple HbS molecules
• => Sickling of RBC

Question 8

List 4 factors promoting the sickling of RBCs in SCD

Answer 8

I HAD

• Infection
• Hypoxia
• Acidosis
• Dehydration

Question 9

Symptoms of SCD are caused by which processes?

Answer 9

• Symptoms of Vaso-occlusion
• Symptoms of Sequestration
• Symptoms of haematopoeisis: chipmunk fascies, hepatomegaly
• Symptoms of Haemolytic Anaemia: jaundice

Question 10

List some of the complications of a vaso-occlusive crisis in SCD

Answer 10

• Joints - dactylitis, avascular necrosis
• Retina- retinal ischaemia= visual disturbance
• CNS - strokes, convulsions, cognitive impairment
• Lungs - acute chest syndrome= SOB, cough,
• Spleen - auto-splenecomy + atrophy, infections
• Abdo - mesenteric ishchaemia + abdo pain
• Lungs- acute chest syndrome- SOB, cough, pain
• Renal necrosis = haematuria, proteinuria
• Penis - priapism

Question 11

State a complication of splenic sequestration and atrophy in SCD

Answer 11

Vulnerable to encapsulated bacteria: S. pneumonia, N. meningitiides, salmonella, H. influenza

Question 12

What can be seen in a blood film of someone with SCD?

Answer 12

Sickle cells

Howell Jolly bodies (nuclear remnants caused by hyposplenism)

Question 13

What test can confirm a diagnosis of SCD?

Answer 13

Electrophoresis

Would see HbS, low HbA and higher HbF and A2

Question 14

How would you manage a patient presenting with an acute painful crisis?

Answer 14

Sickle Acute Painful Crisis

• Saturations- O2
• Antibiotics- if crisis was precipitated by infection
• Pain relief- analgesia
• Cannulation- IV fluids

Question 15

Describe the conservative, medical and surgical management of someone with SCD

Answer 15

• Conservative:
  
  • avoid triggers
• Medical:
  
  • Blood transfusion if severe
  • Hydroxyurea
  • Prophylactic antibiotics
  • Vaccination against encapsulated bacteria (meningits and pneumococcal vaccine)
• Surgical:
  
  • Bone Marrow Transplant which is potentiall curative

Question 16

Explain how hydroxyurea provides relief for people with SCD

Answer 16

Hydroxyurea activates gamma globin production

This increases the production of HbF > HbS