Why do people with hemophilia continue to bleed?

Hemophilia means that the fibrin net does not get made properly. Without the fibrin net, the platelet plug falls out and bleeding continues.

Why does this happen? With hemophilia, one of the 14 clotting factors does not work properly. When a blood vessel is torn, usually the blood vessel constricts and the platelets make a plug. The clotting factors start giving each other directions: factor III, for example, directs factor VII. But then something doesn't work right. Somewhere along the way, using the relay race example, one of the factors drops the relay baton - the directions for blood clotting. It does not alert the next factor in line, so the rest of the factors can't continue their work. The relay race is over. The creation of the fibrin net stops and the bleeding continues.

Adapted from Tell Them the Facts! By Laureen A. Kelley, 1995