When most people get a cut, the body naturally protects itself. Sticky cells in the blood called platelets go to where the bleeding is and plug the hole. This is the first step in the clotting process. When the platelets plug the hole, they release chemicals that attract more sticky platelets and also activate various proteins in the blood known as clotting factors. These proteins mix with the platelets to form fibers, and these fibers make the clot stronger and stop the bleeding.
Our bodies have 12 clotting factors that work together in this process (numbered using Roman numerals from I through XII). Having too little of factors VIII (8) or IX (9) is what causes hemophilia. A person with hemophilia will lack only one factor, either factor VIII or factor IX, but not both. There are two major kinds of hemophilia: hemophilia A, which is a factor VIII deficiency; and hemophilia B, which is a factor IX deficiency.
People with hemophilia may bruise and bleed easily, and they may bleed a lot or for a long time after an injury. Bleeding can occur anywhere in the body, such as into the joints, muscles, or digestive tract. Some people have mild disease, some moderate, and some more severe.
Hemophilia is a genetic disorder, which means it's the result of a change in genes that was either inherited (passed on from parent to child) or occurred during development in the womb. Hemophilia almost always occurs in males, but in rare cases can affect females.
Decreased factor IX activity may be related to:
- Hemophilia B (a bleeding disorder caused by a lack of blood clotting factor IX)
- Disorder in which the proteins that control blood clotting become over active (disseminated intravascular coagulation)
- Fat malabsorption (not absorbing enough fat from your diet)
- Liver disease (such as cirrhosis)
- Vitamin K deficiency
- Taking blood thinners
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