Sickle Cell Anaemia

Question 1

What is sickle cell anaemia and what is its inheritance pattern?

Answer 1

1. Production of abnormal haemoglobin results in vaso-occlusive crises. Common in those of African origin.
2. Autosomal recessive - AA substitution causing HbS instead of HbA

Question 2

What is the difference between homozygous and heterozygous sickle cell anaemia?

Answer 2

1. Homozygous - HbSS

2. Heterozygous - HbAS, no disability.

Question 3

What is the pathogenesis of sickle cell anaemia?

Answer 3

HbS polymerises when deoxygenated, causing RBCs to deform, producing sickle cell, which are fragile and haemolyse. They also block small vessel.

Question 4

What are the tests done to confirm sickle cell anaemia?

Answer 4

1. Haemolysis is variable
2. Low Hb, high reticulocytes, high bilirubin
3. Film - sickle cell and target cells
4. Hb electrophoresis confirms diagnosis and distinguishes from SS/AS.
5. Diagnosis at birth using skin prick heel test.

Question 5

What can trigger a sickle cell crisis?

Answer 5

Dehydration, infection, cold, damp, unaccustomed exercise, stress, pregnancy, operations.

Question 6

What specific things should you examine in someone with sickle cell anaemia?

Answer 6

Obs, auscultate heart and lungs, palpate liver and spleen, pallor, jaundice, skin ulcers, bony pain, oedema.

Question 7

What is this describing?
Sickle cell, severe bone pain, hands and feet affected in <3yrs. Mesenteric ischaemia mimics acute abdomen. CNS infarction can cause stroke/seizures. Avascular necrosis of femoral head/shoulder. Priapism.

Answer 7

Vaso-occlusive crisis

Question 8

What is this describing?

Sickle cell, parvovirus B19, sudden RBC production drop. Self-limiting <2wks, few need transfusion.

Answer 8

Aplastic crisis

Question 9

What is this describing?
Sickle cell, mainly affects children. Pooling of blood in spleen +/- liver, organomegaly, severe anaemia and shock. Urgent transfusion needed.

Answer 9

Sequestration crisis

Question 10

What is this describing and how is it treated?
Sickle cell. Pain, fever, tachypnoea, wheeze, cough, pleuritic pain, hypoxia, SOB. Caused by pulmonary infiltrates from fat embolism originating from bone marrow or infection.

Answer 10

1. Acute chest crisis

2. Oxygen, analgesia, antibiotics, bronchodilators.

Question 11

How do you manage crisis in sickle cell anaemia?

Answer 11

1. Prompt, generous analgesia (IV opiates), most will have personalised plan.
2. Crossmatch blood, check FBC and reticulocyte count.
3. Septic screen, blood cultures, MSU, CXR, if fever or chest signs.
4. IVF, oxygen
5. Blood transfusion of Hb drops
6. Empirical Abx if fever or chest signs
7. PCA if oral analgesia does not control pain.

Question 12

How is chronic sickle cell anaemia managed?

Answer 12

1. Hydroxyurea if frequent crises (increases HbF)
2. Splenic infarction leads to hyposplenism and immunocompromised: daily penicillin V and immunisation.
3. Bone marrow transplant can be curative.

Question 13

What are the complications of sickle cell anaemia?

Answer 13

1. Splenic infarction due to vascular occlusion.
2. Stroke
3. Poor growth
4. Chronic renal failure
5. Gallstones
6. Retinal disease
7. Iron overload from transfusions
8. Pulmonary hypertension