Sickle Cell Disease
An inherited haemoglobinopathy in which abnormal haemoglobin S polymerises when deoxygenated, distorting red cells into rigid sickles that occlude small vessels and haemolyse, so hypoxia, dehydration, cold and infection all precipitate the same vaso-occlusive crisis.
First principles
A single amino acid substitution changes how haemoglobin behaves when oxygen is low
A point mutation in the beta-globin gene produces haemoglobin S, which behaves normally when oxygenated but polymerises into rigid rods when deoxygenated, physically distorting the red cell into a sickle shape. Early sickling is reversible on reoxygenation, but repeated cycles progressively damage the cell membrane until the change becomes permanent. The entire disease follows from this one structural quirk of a single protein.
Educational content pending clinical review. Not medical advice.