Sickle cell anaemia

Question 1

Overview of sickle cell anaemia

Answer 1

Genetic condition - causes sickle shaped RBCs
- Autosomal recessive

Makes RBCs more fragile and easily destroyed - leading to haemolytic anaemia

Patientss with sickle cell are prone to various sickle cell crises

Question 2

Pathophysiology of sickle cell

Answer 2

Patients with sickle cell have abnormal variant of haemoglobin called haemoglobin S (HbS) - gives RBC sickle shape

Autosomal recessive condition where there is an abnormal gene for beta-globin on chromosome 11

One copy of the gene results in sickle cell trait
- These patients are usually asymptomatic

2 abnormal copies required for sickle cell disease

Question 3

Relation to malaria (sickle cell)

Answer 3

More common in patients from areas traditionally associated with malaria:
– Africa, India, ME, Caribbean

Sickle cell trait (1 copy of gene) reduces severity of malaria (selective advantage)

Question 4

Diagnosis and testing:

Answer 4

Pregnant women at risk of being carriers or the gene are offered testing during pregnancy

Tested for on newborn heel prick test at 5 days

Question 5

Complications of sickle cell:

Answer 5

Anaemia

Increased risk of infection

Stroke

Avascular necrosis in large joints (e.g. hip)

Pulmonary hypertension

Painful and persistent penile erection (priapism)

CKD

Sickle cell crises

Acute chest syndrome

Question 6

General management of sickle cell:

Answer 6

Avoid dehydration - and other triggers of crisis

Up to date vaccination

Antibiotic prophylaxis - penicillin V (phenoxymethypenicillin)

Hydroxycarbamide - used to stimulate production of foetal haemoglobin (HbF)

• HbF does not lead to sickling of RBCs)
• Has protective effect against sickle cell crises and acute chest syndrome

Blood transfusion - for severe anaemia

Bone marrow transplant - can be curative

Question 7

Hydroxycarbamide

Answer 7

• used to stimulate production of foetal haemoglobin (HbF)
• HbF does not lead to sickling of RBCs)
• Has protective effect against sickle cell crises and acute chest syndrome

Question 8

Sickle cell crises:

Answer 8

Umbrella term for spectrum of acute crises related to condition

Can be spontaneous or triggered by stresses such as:

• infection
• dehydration
• cold
• significant life events

Question 9

Management of sickle cell crises:

Answer 9

No specific treatment - managed supportively

• Low threshold for hospital admission
• Treat any infection
• Keep warm
• Keep well hydrated - (IV fluids may be required)
• Simple analgesia - such a paracetamol or ibuprofen
• Penile aspiration for priapism

NSAIDs - avoided where there is renal impairment

Question 10

Vaso-occlusive Crisis (AKA painful crisis)

Answer 10

Sickle shaped blood cells clogging capillaries causing distal ischaemia.

Associated with dehydration and raised haematocrit

Symptoms typically are:

• pain
• fever
• symptoms of infection causing it
• Priapism - trapping blood in penis (urological emergency treated with aspiration of blood from the penis)

Question 11

Splenic Sequestration Crisis

Answer 11

Caused by RBCs blocking blood flow within the spleen.

Causes:
- acutely enlarged and painful spleen.

• severe anaemia and circulatory collapse (hypovolaemic shock)
  (From the pooling of blood in spleen )

Splenectomy:

• prevents sequestration crisis
• often done in cases of recurrent crisis
• recurrent crisis can lead to splenic infarction and therefore susceptibility to infections

Question 12

Aplastic Crisis (and what triggers it)

Answer 12

Aplastic crisis describes a situation where there is a temporary loss of the creation of new blood cells.

This is most commonly triggered by infection with parvovirus B19.

Leads to significant anaemia

Question 13

Management of aplastic crisis:

Answer 13

Management is usually supportive - blood transfusions if necessary

Usually resolves spontaneously within a week

Question 14

Diagnosis of Acute Chest Syndrome:

Answer 14

Diagnosis requires both:

• Fever or respiratory symptoms
• New infiltrates seen on CXR

Question 15

Acute chest syndrome

Answer 15

Can be due to:

• infection
  
  • • e.g. pneumonia, bronchiolitis
• non-infective causes
  
  • • e.g. pulmonary vaso-occlusion OR fat emboli

Medical emergency with high mortality
- requires prompt supportive management and treatment of the underlying cause

• Antibiotics or antivirals – for infection
• Blood transfusions – for anaemia
• Inventive spirometry – using a machine that encourages effective and deep breathing
• Artificial ventilation

Question 16

Management of acute chest syndrome:

Answer 16

Medical emergency with high mortality
- requires prompt supportive management and treatment of the underlying cause

Treatment/ supportive management:
- Antibiotics or antivirals – for infection

• Blood transfusions – for anaemia
• Inventive spirometry – using a machine that encourages effective and deep breathing
• Artificial ventilation