Words to know: Hemophilia and bleeding disorders
- Hemophilia
- An inherited condition where blood does not clot well because a clotting factor is low or missing.
- Clotting factor
- A protein in the blood that helps form clots to stop bleeding.
- Factor VIII
- The clotting factor that is low in hemophilia A.
- Factor IX
- The clotting factor that is low in hemophilia B.
- Carrier
- A person, usually a woman, who has one copy of the hemophilia gene and can pass it on. Some carriers have bleeding problems.
- X-linked
- A trait carried on the X chromosome. X-linked conditions mostly affect males.
- Von Willebrand disease
- The most common inherited bleeding disorder, caused by a low or poorly working von Willebrand factor.
- Hemarthrosis
- Bleeding into a joint.
- Target joint
- A joint that bleeds again and again.
- Hemophilic arthropathy
- Lasting joint damage caused by repeated bleeding.
- Prophylaxis
- Regular treatment given to prevent bleeds.
- On-demand treatment
- Treatment given only after a bleed starts.
- Recombinant
- Made in a lab using cells, not from human blood.
- Extended half-life
- A medicine changed to last longer in the body, so it is needed less often.
- Inhibitor
- An antibody the body makes against the factor used in treatment, which makes the factor work poorly.
- Bethesda assay
- A blood test that measures how strong an inhibitor is.
- Bypassing agent
- A medicine that helps blood clot by going around the missing factor. Used when inhibitors are present.
- Emicizumab
- A shot for hemophilia A that does the job of factor VIII to prevent bleeds.
- Rebalancing therapy
- A medicine that lowers the body's natural anti-clotting proteins so the blood can clot better.
- Gene therapy
- A treatment that gives the body a working gene so it can make its own clotting factor.
- Desmopressin (DDAVP)
- A medicine that releases stored factor VIII and von Willebrand factor into the blood.
- Tranexamic acid
- A medicine that helps clots hold together, often used for mouth and nose bleeding.
- aPTT
- A blood test that measures how long blood takes to clot. It is often long in hemophilia.
- Hemophilia treatment center
- A specialty clinic with a full team that cares for people with bleeding disorders.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.