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Definition: haemophilia from Philip's Encyclopedia

Hereditary blood clotting disorder causing prolonged external or internal bleeding, often without apparent cause. Haemophilia A is caused by inability to synthesize blood factor VIII, a substance essential to clotting. This can be managed with injections of factor VIII. The rarer haemophilia B is caused by a deficiency of blood factor IX. The gene for both types is passed on almost exclusively from mother to son.

Summary Article: Hemophilia
from Encyclopedia of Human Genetics and Disease


Most common in males; Hemophilia A, 1 in 400 to 1 in 5,000 males; Hemophilia B, 1 in 20,000 newborn males worldwide

Other Names

hemophilia, familial; hemophilia, hereditary; Type B Christmas disease or hemophilia B Leyden.

Hemophilia is an old and important disease affecting the welfare of states and kingdoms. Among the first early references was a statement in the Jewish Talmud, written in the second century, that a mother who has had two sons who have died with bleeding disease did not have to have the third one circumcised. Albucasis, an Arab physician, described several families whose males died after minor accidents. Several other allusions to bleeding disease have appeared in historical writings. However, the first account in the nineteenth century was written by Dr. John Otto, a Philadelphia doctor, who described “bleeders” in certain families and then later traced the same condition back to a woman who came to Plymouth in 1720. He implied here a link to women and X-linked genetic conditions.

Sometimes, hemophilia is called “the royal disease” because it was carried in the European royalty. Queen Victoria, who ruled the British Empire throughout most of the nineteenth century, passed the disorder to several of her female descendants. These women became members of the royalty in Spain, Germany, and Russia. Perhaps the most important case was in Russia, where hemophilia played a big part in the Russian Revolution of 1917.

What Is Hemophilia?

Hemophilia is a rare bleeding disorder in which the blood does not clot normally. Following an injury or even a simple cut, the person may bleed profusely. Having surgery or even having a tooth pulled may involve prolonged bleeding. Also, spontaneous bleeding may occur internally without a cut and affect joints, muscles, brain, or other internal organs. A mild form may not involve the profuse and spontaneous bleeding and does not show up unless the person has a tooth pulled or surgery.

A hemophiliac boy in North Carolina, eight years old, prepares his twice-weekly injection of a very expensive medication that his family was able to afford by being enrolled in the Children's Health Insurance Program (CHIP), after being on a waiting list.

(Photo by Steve Liss/Time & Life Pictures/Getty Images) (Steve Liss/Contributor / Time & Life Pictures/Getty Images)

The word “hemophilia” comes from two Greek roots: hemo, meaning “blood,” and philos, meaning “love.” Hence, the condition reflects the inability of the body to stop bleeding. People with hemophilia have little or no blood clotting factors, essential elements for controlling bleeding. These protein factors work with blood platelets to form the clot. There are two main types of hemophilia, which have similar characteristics. Both have the missing factors that are essential for blood clotting. Internal bleeding may occur with either type. Following are the two main types of hemophilia, which are dependent upon two blood factors:

  • Hemophilia A (known as classic hemophilia): People with this most common form of the disorder have a deficiency in clotting factor VIII.

  • Hemophilia B (known as hemophilia B Leyden or Christmas disease): People with this rarer form have a deficiency in clotting factor IX.

Acquired hemophilia is a form of the disease that is not inherited and is characterized by abnormal bleeding in the skin and muscles, and usually begins in adulthood.

What Are the Genetic Causes of Hemophilia?

Two mutated X-linked genes are responsible for hemophilia: F8 and F9. Because it is X-linked, the condition is more common in males. Women who are carriers of the defective gene may experience some mild symptoms. In about one-third of the cases, no family history of hemophilia exists; the disorder appears to be a spontaneous mutation.

F8 Gene

Mutations in the F8 gene, officially called the “coagulation factor VIII, procoagulant component” gene, cause hemophilia A. Normally, F8 provides instructions for the protein coagulation factor VIII that is essential for the formation of blood clots. When one is injured, the clots seal off the damaged blood vessels to prevent loss of blood. Made by the cells in the liver, factor VIII roams around the bloodstream in an inactive form. It is bound to a molecule called the von Willebrand factor. When a cut occurs, factor VIII rushes to the site and interacts with another factor called factor IX. The two initiate a chain reaction to cause a clot.

Most of the approximately 1,300 mutations in F8 involve an exchange of only one base pair of proteins. Other mutations may delete or insert certain base pairs. The change in the gene produces a defective or missing protein, which cannot aid in blood clotting. As a result the symptoms of hemophilia occur. F8 is inherited in an X-linked recessive pattern and is located on the long arm (q) of the X chromosome at position 28.

F9 Gene

Mutations in the F9 gene, officially called the “coagulation factor IX,” lead to Hemophilia B. Normally, F9 instructs for a protein called coagulation factor IX, which is essential for blood clotting. It is also made in the liver and circulated in an inactive form until injury occurs. When an injury happens, the coagulation factor IX interacts with factor VIII and helps form the very important blood clot.

More than 900 mutations in F9 involve changes in a single DNA building block. The abnormal genes cause a disruption in work of the coagulation factor IX protein to enable clotting and evokes the symptoms of hemophilia. F9 is inherited in a recessive X-linked pattern and is located on the long arm (q) of the X chromosome at position 27.1-q27.2.

What Are the Treatments for Hemophilia?

Currently, no cure exists for hemophilia. Treatment is available, but it is costly and requires lifelong infusion or clotting factor that is made from human plasma or recombinant technology. In the 1980s, most of the people with severe hemophilia became infected with HIV/AIDS because of contamination of the blood supply. However, since 1986, the regulations and methods of blood transfusion have improved, and the blood supply is now safe. Ryan White was a young American hemophiliac whose story helped to call attention to the problem of the contamination in the blood supply.

Further Reading
  • F8.” 2010. Genetics Home Reference. National Library of Medicine (U.S.). Accessed 5/18/12.
  • F9.” 2010. Genetics Home Reference. National Library of Medicine (U.S.). Accessed 5/18/12.
  • Hemophilia.” 2010. Genetics Home Reference. National Library of Medicine (U.S.). Accessed 5/18/12.
  • National Hemophilia Foundation. Accessed 5/18/12.
  • What Is Hemophilia?” 2011. National Heart, Lung, and Blood Institute. Accessed 2/2/11.
  • Copyright 2013 by Evelyn B. Kelly

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