A bleeding disorder is present when the blood does not clot properly. Blood clotting is a complex process that involves as many as 20 different plasma proteins. All clotting proteins and platelets need to work effectively and in the correct order to form a proper clot that is strong enough to stop bleeding. A bleeding disorder occurs when the body is unable to activate the entire “clotting cascade” correctly.

The body initiates the clotting cascade when an injury occurs. At a high level, coagulation works as follows:

1. Blood vessels constrict – When an injury occurs, the blood vessel at the site of injury contracts to limit the flow of blood to the damaged area.
2. Platelet plug forms – Within seconds of the injury occurring, small cells found in the blood, called platelets, spread on top of the injured vessel and release chemical signals to attract other cells circulating in the blood. Some of the cells attracted are clotting factors. The first factor to be activated during the clotting cascade is the von Willebrand factor. VWF is a glue-like protein that forms a plug that prevents blood from flowing to the site of injury.
3. Fibrin clot is created – Thirteen clotting factors (represented with roman numerals I – XIII) along with calcium, vitamin K and other proteins work together in a series of complex chemical reactions to form a “fibrin clot.” The fibrin clot acts as a net over the wound. Depending on the size of the injury, the fibrin clot strengthens over several days or weeks, and when the wound is healed, the fibrin clot dissolves.

If any of the steps in the clotting cascade don’t work properly or are deficient, the person bleeds longer and, therefore, has a bleeding disorder. The type and severity of the disorder is determined based on the protein that is missing from the blood and how much of it is missing.

*Resources taken from Hemophilia Federation of America