Hemophilia is a hereditary bleeding disorder caused by a deficiency in one of two blood clotting factors: factor VIII or factor IX.
- Several different gene abnormalities can cause the disorder.
- Blood tests are needed for diagnosis.
- People bleed unexpectedly or after minor injuries.
- Transfusions are given to replace missing clotting factors.
Clotting factors are proteins that interact to help the blood clot, stopping bleeding.
There are two forms of hemophilia.
- Hemophilia A, which accounts for about 80% of all cases, is a deficiency in clotting factor VIII.
- Hemophilia B is a deficiency in clotting factor IX.
The bleeding patterns and consequences of these two types of hemophilia are similar.
Hemophilia is caused by several different gene abnormalities. They are sex-linked, which means that the gene abnormalities are inherited through the mother and that nearly everyone with hemophilia is male (see also X-Linked Inheritance).
The main symptom is excessive bleeding. The bleeding may be into a joint or muscle, inside the abdomen or head, or from cuts, dental procedures, or surgery. A child who has hemophilia bruises easily.
The severity of the bleeding depends on how a particular gene abnormality affects the blood clotting activity of factor VIII or IX.
- Mild hemophilia: Clotting activity is 5 to 25% of normal
- Moderate hemophilia: Clotting activity 1 to 5% of normal
- Severe hemophilia: Clotting activity less than 1% of normal
- Replace the deficient clotting factor
People who have hemophilia should avoid situations that might provoke bleeding and should avoid drugs (for example, aspirin and probably also nonsteroidal anti-inflammatory drugs) that interfere with the function of platelets. They should be conscientious about dental care so that they will not need to have teeth extracted. If people who have milder forms of hemophilia need to have dental or other surgery, the drugs aminocaproic acid or desmopressin may be given to improve temporarily the body’s ability to control bleeding so that transfusions can be avoided.
Often, treatment involves transfusions to replace the deficient clotting factor. These factors are normally present in the liquid component of blood (plasma). Clotting factors may be obtained from donated blood by concentrating or purifying them from plasma. Clotting factors purified from plasma are treated to inactivate most of the viruses that might be present in the donated plasma. Clotting factors also may be produced in a laboratory using special technological procedures. These manufactured clotting factors are called highly purified recombinant factor concentrates. Recombinant forms of both factor VIII and IX are available. Because recombinant forms are not obtained from human donors, they do not have the slight risk of infection that is present with factors derived from donated blood. The dose, frequency, and duration of therapy are determined by the site and severity of the bleeding problem. Clotting factors may also be used to prevent bleeding before surgery or at the first sign of bleeding.