Sickle cell disease - emergency medicine revision
Sickle cell disease (SCD) is a group of inherited haemoglobinopathies defined by the presence of sickle haemoglobin (HbS). It produces chronic haemolytic anaemia, episodic vaso‑occlusion with severe pain and organ ischaemia, and progressive end‑organ damage.
Emergency clinicians must recognise time‑sensitive complications, begin immediate stabilisation, and escalate promptly to haematology, paediatrics, obstetrics or critical care when indicated.
Key learning aims
- Understand the genetic basis and pathophysiology that explain common ED presentations.
- Recognise major acute complications and their distinguishing features.
- Know the immediate ED investigations and initial management priorities, including escalation “red flags.”
- Be aware of screening, prevention and specialist curative options relevant to follow‑up.
Pathophysiology and genetics (concise)
- Normal adult haemoglobin (HbA) = α2β2; foetal haemoglobin (HbF) = α2γ2.
- HbS arises from a single β‑globin mutation (glutamic acid → valine on chromosome 11).
- Under deoxygenation, HbS polymerises and deforms erythrocytes into sickled shapes.
- Repeated sickling causes membrane damage, chronic haemolysis (RBC lifespan ≈ 20 days), endothelial dysfunction and microvascular occlusion leading to vaso‑occlusive crises (VOC) and organ infarction.
- Recurrent splenic infarction causes functional hyposplenism with increased susceptibility to encapsulated organisms.
- Common genotypes: HbSS (sickle cell anaemia, typically most severe), compound heterozygotes (e.g., HbSC, HbSβ‑thalassaemia), and HbAS (trait).