People with the inherited bleeding disorder haemophilia lack factors that cause the blood to clot. The disease affects thousands of people around the world and has even played a part in historic events. By Neil Savage.
When damage occurs to blood vessels, exposure of the blood to collagen in the cell walls and material released by the cells triggers the activation of clotting factors. One factor activates the next factor in a series of events (some not depicted here) that eventually produces fibrin. Fibrin forms a mesh to hold together a plug of platelets to form a clot (platelets are a type of cell that circulates in the blood to help coagulation)1,2.
OF ALL THE PEOPLE WITH HAEMOPHILIA...
THE ROYAL DISEASE
The mutations causing haemophilia are carried on the X chromosome. Woman are usually carriers, with a 50% chance of having sons with haemophilia or daughters who are carriers. Men with haemophilia will have no sons who are haemophiliacs, but all their daughters will carry the gene. In rare cases, female carriers or girls with both X chromosomes affected will have haemophilia; fewer than 10% of cases occur in females. Approximately one-third of cases arise from spontaneous mutation5.