Blood cells called platelets are very important for blood clotting. These cells have a sticky surface that allows them to clump together to stop the flow of blood.
Platelets
also need clotting factors. These are proteins that form a "web"
around the platelets, helping them to stay in place.
The
mutated haemophilia gene means a child with the condition doesn't have enough
clotting factors in their blood.
Several
different clotting factors are present in the blood. They are numbered using
roman numerals. For example, in haemophilia A there's not enough clotting
factor VIII (8) in the blood. In haemophilia B, there's not enough clotting
factor IX (9) in the blood.
