What Is Hemophilia?
Hemophilia (heem-o-FILL-ee-ah) is a rare, inherited
bleeding disorder in which your blood doesnt clot normally. If you have
hemophilia, you may bleed for a longer time than others after an injury. You
also may bleed internally, especially in your knees, ankles, and elbows. This
bleeding can damage your organs or tissues and, sometimes, be fatal.
People born with hemophilia have little to none of a
protein needed for normal blood clotting. The protein is called a clotting
factor. There are several types of clotting factors, and they work together
with platelets to help the blood clot. Platelets are small pieces of blood
cells that are formed in the bone marrow. They play a major role in blood
When blood vessels are injured, clotting factors
help the platelets stick together to plug cuts and breaks at the site of the
injury to stop the bleeding. Without clotting factors, normal blood clotting
cant take place. Sometimes people with hemophilia need injections of a
clotting factor or factors to stop bleeding.
There are two main types of hemophilia. If you have
hemophilia A, you have little to no clotting factor VIII (8). About 9 out of 10
people with hemophilia have type A. If you have hemophilia B, youre
missing or have low levels of clotting factor IX (9).
Hemophilia can be mild, moderate, or severe,
depending on how much clotting factor is in the blood. About 7 out of 10 people
who have hemophilia A have the severe form of the disorder. People who
dont have hemophilia have a factor VIII activity of 100 percent; people
who have severe hemophilia A have a factor VIII activity of less than 1
In addition to being inherited, hemophilia also can
be acquired, which means that you can develop it during your lifetime. It can
develop if your body forms antibodies to the clotting factors in your
bloodstream. The antibodies can block the clotting factors from working. Only
inherited hemophilia is discussed in this article.
About 18,000 people in the United States have
hemophilia. Each year, about
400 babies are born with the disorder.
Hemophilia usually occurs only in males (with very rare exceptions).