Sickle cell disease
Description
- HBB point mutation, chromosome 11: glutamate -> valine at codon 6 -> haemoglobin S
- Deoxygenated HbS is poorly soluble -> polymerises -> rigid sickled cell
Genotypes
| Severity | |
|---|---|
| HbSS (sickle cell anaemia) | Most severe; ~60-70% of disease |
| HbS/beta0-thal | Equivalent to SS |
| HbSC | Milder anaemia but more retinopathy, avascular necrosis, and proliferative eye disease; larger spleen retained |
| HbS/beta+-thal | Mild-moderate |
| HbAS (trait) | *Not a disease* |
Two pathological arms
- Vaso-occlusion - adhesion, inflammation, ischaemia-reperfusion -> pain, acute chest, stroke, organ infarction
- Haemolysis - free plasma Hb scavenges NO -> endothelial dysfunction, pulmonary hypertension, priapism, leg ulcers
- Different complications track with different arms - HbSC sits at the vaso-occlusive end
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