Hemophilia A and B: Similar, Yet Different

Hemophilia A and B: Similar, Yet Different

Hemophilia is caused by a deficiency or absence of a protein in the blood that helps the blood coagulate (clot) after injury or trauma, such as experiencing a blunt blow to part of the body. The key to treating hemophilia is to replace this protein, called a coagulation factor, with a concentrate of a "healthy" (normal) coagulation protein.

Years ago, replacement coagulation factors were derived from the plasma of healthy blood donors. More recently, they have been manufactured in a laboratory using a process called recombinant technology to mimic natural coagulation factors in every aspect. Recombinant coagulation factors are inherently safer and more convenient to store and use than are plasma-derived coagulation factors, but they also are more expensive.

Hemophilia A, caused by a deficiency in coagulation factor VIII, is four times more frequent than hemophilia B, which is caused by a lack of factor IX. The signs and symptoms of hemophilia A and B are almost the same. Both forms of the disease cause bleeding in the joints and changes in blood that prolong bleeding time. However, hemophilia A is associated with more severe genetic mutations than is hemophilia B, so more people with hemophilia A tend to have severe disease.

Just as hemophilia A differs from hemophilia B, replacement therapy for these two types of hemophilia is somewhat different. For example, factor replacement therapy for hemophilia A tends to control bleeding for a shorter time than does treatment for hemophilia B. This explains why joint bleeding and the need for total joint replacement are more common in people with hemophilia A.

What Does This Mean to People With Hemophilia?

Even though there are basic differences between hemophilia A and B, people with these two types of the disease basically are treated the same. Whether individuals have mild, moderate, or severe disease depends upon how much natural clotting factor they have when they are diagnosed. This information is important for doctors to consider when they select what replacement factor to prescribe, what dose should be given, and what treatment schedule to recommend.

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