Words and Phrases to Know


A condition in which the blood is deficient in red blood cells, in hemoglobin (the iron-carrying component) or in total volume from loss of blood.

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Bethesda Unit
A laboratory measurement of an antibody, called an inhibitor. Values above 5 are considered high; the inhibitor is powerful and weakens the effect of clotting factor.

The escape of blood from vessels.

Bleeding Disorder
Several chronic health disorders in which the body does not clot properly, resulting in excessive or lengthy bleeding. Also called bleeding conditions.

Blood Clot
A coagulated mass produced by clotting of blood.

Blood Vessel
Any of the tubular structures through which blood circulates in the body; a vein, artery or capillary.

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A person who has the gene for a condition, but does not necessarily display the symptoms.

Central Venous Access Device (CVAD)
A small, flexible tube placed in a vein for patients who need regular infusions.

Christmas Disease
A hereditary sex-linked hemorrhagic disorder involving absence of coagulation factor IX in the blood and failure of the clotting mechanism—called also hemophilia B.

Structures in the cell’s nucleus that contain genetic information in the form of DNA.

Clotting Factor
Proteins in the blood that act in sequence to stop bleeding and form a clot.

The process of forming a blood clot.

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The art or act of identifying a disease from its signs and symptoms.

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Extended Half-life Factor
A type of factor that can stay in the bloodstream longer, which may result in a patient needing less frequent prophylaxis to prevent bleeds.

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Factor Replacement Therapy
Treatment that is infused to replace the body’s missing clotting proteins. Factor product is made from plasma or recombinant products.

A white insoluble fibrous protein formed from fibrinogen by the action of thrombin especially in the clotting of blood.

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A sequence of DNA that occupies a specific location on a chromosome and determines a particular characteristic.

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The time taken for half of infused factor activity to disappear from the bloodstream.

Bleeding into a joint.

Hemophilia A or B
A bleeding disorder in which a clotting factor protein, such as factor VIII (hemophilia A) or IX (hemophilia B), is completely or partially lacking or does not function normally.

  • Mild hemophilia—a factor VIII or IX level ranging from 5% up to 50% of normal blood levels.
  • Moderate hemophilia—a factor VIII or IX level ranging from 1% up to 5% of normal blood levels.
  • Severe hemophilia—a factor VIII or IX level below 1% of normal blood levels.

Rapid, uncontrollable bleeding.

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Treatment (as by vaccination) of an organism for the purpose of making it immune to a particular pathogen.

Derived from the biological process of transmitting certain characteristics or conditions from parents to offspring.

Inhibitor (Treatment Inhibitor)
An antibody to infused clotting factor concentrates, making the treatment ineffective.

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Menstrual periods with abnormally heavy or prolonged bleeding. Typically, it’s a period that lasts longer than 7 days, along with heavy bleeding that limits daily activities or passage of blood clots larger than a quarter. It’s a common symptom of von Willebrand disease (vWD) in women.

A change in the DNA of a cell, due to such causes as exposure to radiation or viruses, or during cell division. For instance, Congenital Hemophilia A is caused by a cell mutation.

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An abbreviation for polyethylene glycol molecules, which are synthetic polymers. A chemical modification with PEG, called PEGylation, may prolong the half-life of a drug.

A method for prolonging the half-life of protein products.

Yellow-colored, protein-rich portion of the blood, which carries the red blood cells, white blood cells and platelets.

Tiny plate-like components of blood that help seal injured blood vessels and stop bleeding.

A treatment regimen to prevent bleeds.

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Recombinant Factor
Genetically engineered factor product made without human blood products, decreasing the risk of transmission of bloodborne infections.

Rest, ice, compression, elevation—used especially for the initial treatment of many usually minor sports-related injuries (as sprains).

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The formation of a blood clot.

A measure of the concentration of antibodies, called inhibitors, in the blood.

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Von Willebrand Disease
An inherited bleeding disorder characterized by either decreased or defective von Willebrand factor (VWF).

Von Willebrand Factor
A blood clotting protein that binds clotting protein factor VIII and platelets in blood vessel walls to help form a platelet plug during the clotting process.

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Hemophilia Emergency Care

Before an emergency arises, people with hemophilia and their caregivers can follow these tips to prepare for the emergency room.