What Is Hemophilia?

 

What Is Hemophilia?

Hemophilia (heem-o-FILL-ee-ah) is a rare bleeding disorder in which your blood doesn't 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 may be life threatening.

 

 

Overview

Hemophilia usually is inherited. This means that the disorder is passed from parents to children through the genes.

People born with hemophilia have little or no clotting factor. Clotting factor is a protein need for normal blood clotting. There are several types of clotting factors. These proteins work with platelets (PLATE-lets) to help the blood clot.

Platelets are small blood cell fragments that form in the bone marrow—a sponge-like tissue in the bones. Platelets play a major role in blood clotting.

When blood vessels are injured, clotting factors help platelets stick together to plug cuts and breaks at the site of the injury and stop bleeding. Without clotting factors, normal blood clotting can't take place. Some people who have 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're missing or have low levels of clotting factor VIII (8). About 9 out of 10 people who have hemophilia have type A. If you have hemophilia B, you're missing or have low levels of clotting factor IX (9).

Rarely, hemophilia can be acquired. This means that you can develop it during your lifetime. This can happen if your body forms antibodies (proteins) to the clotting factors in your bloodstream. The antibodies can prevent the clotting factors from working.

This article focuses on inherited hemophilia.

 

Outlook

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 don't 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 percent.

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).

Revised July 2009