National Organization for Rare Disorders, Inc.
- Christmas disease
- Factor IX deficiency
- royal disease
Hemophilia B is a rare genetic bleeding disorder in which affected individuals have insufficient levels of a blood protein called factor IX. Factor IX is a clotting factor. Clotting factors are specialized proteins needed for blood clotting, the process by which blood seals a wound to stop bleeding. Individuals with hemophilia B do not bleed faster than unaffected individuals, they bleed longer. This is because they are missing a protein involved in blood clotting and are unable to effectively stop the flow of blood from the site of a wound. This is sometimes referred to as prolonged bleeding or a bleeding episode.
Hemophilia B is classified as mild, moderate or severe. In mild cases, bleeding symptoms may occur only after surgery, major injury or a dental procedure. In some moderate and most severe cases, bleeding symptoms may occur after a minor injury or spontaneously with no known cause.
Hemophilia B is caused by disruptions, or changes, to the factor IX gene. The factor IX gene is located on one of two sex chromosomes - the X chromosome. Males have one X chromosome and one Y chromosome and thus one altered copy of the factor IX gene in a male is enough to cause him to have hemophilia. Females have two X chromosomes and must have two altered copies of the factor IX gene to have hemophilia. Hemophilia in females is very uncommon and therefore the disorder almost always affects males. It is possible for some females with only one altered copy of the factor IX gene to have bleeding symptoms most often seen in mild hemophilia.
Hemophilia B is the second most common type of hemophilia and is estimated to occur in about 1 in 25,000 male births. It affects all races equally. Hemophilia B is also known as factor IX deficiency or Christmas disease. The disorder was first reported in the medical literature in 1952 in a patient with the name of Stephen Christmas. The most famous family with hemophilia B was that of Queen Victoria of England. Through her descendants, the disorder was passed down to the royal families of Germany, Spain and Russia and thus hemophilia B is also known as the "royal disease."
Although the focus of this report is the genetic, or inherited, form of hemophilia B, it should be noted that another form called acquired hemophilia B can develop later in life (see "Related Disorders" section below). An individual with acquired hemophilia B is not born with the condition. Acquired hemophilia B is caused by the body's production of antibodies against its own factor IX protein. The factor IX antibodies destroy circulating factor IX in the blood causing bleeding symptoms. Acquired hemophilia B is extremely rare; most cases of acquired hemophilia are in those with hemophilia A.
National Hemophilia Foundation
116 West 32nd Street, 11th Floor
New York, NY 10001
Canadian Hemophilia Society
400-1255 University Street
Quebec, H3B 3B6
NIH/National Heart, Lung and Blood Institute
P.O. Box 30105
Bethesda, MD 20892-0105
World Federation of Hemophilia
1425 René Lévesque Blvd. W. Suite 1010
Quebec, H3G 1T7
Hemophilia Federation of America
210 7th St. SE
Washington, DC 20003
MUMS National Parent-to-Parent Network
150 Custer Court
Green Bay, WI 54301-1243
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
PO Box 241956
Los Angeles, CA 90024
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Last Updated: 8/28/2012
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