In a normally functioning hemostatic response to a tear in a blood vessel, a chain reaction of proteins, called clotting factors, act together in a specific order to form a blood clot. There are at least eleven clotting factors in the body. The deficiency of any one of these factors results in a bleeding disorder.

Hemophilia A is an x-linked genetic bleeding disorder which results in prolonged bleeding. It is also known as Factor VIII Deficiency because of the body’s inability to produce enough of the blood clotting factor VIII.

Hemophilia B is also an x-linked genetic bleeding disorder which results in prolonged bleeding. It results from the body’s inability to produce enough blood clotting Factor IX, and is sometimes called Factor IX Deficiency. It may occasionally be referred to as Christmas Disease in reference to the name of the first patient with the disease to be studied.

The severity of symptoms of Hemophilia A or B can range from mild to severe. In addition to prolonged bleeding time, bleeding within joints may lead to swelling, pain, and permanent joint damage.

Hemophilia A is treated by replacing the deficient clotting factor, Factor VIII, and Hemophilia B by replacing the deficient Factor IX. The factor product is infused intravenously. Some patients treat bleeds in an “on demand” fashion, while others maintain a prophylactic treatment regimen to prevent the long-term effects of Hemophilia, particularly the effects of joint bleeds. Prophylaxis is especially utilized in the treatment of children.

Factor products are either derived from human plasma or developed through monoclonal or recombinant technologies. In the 1980’s and early 1990’s, infectious diseases such as AIDS and Hepatitis A were transmitted to Hemophilia patients through infected plasma used in the manufacturing of factor products. Due to the addition of purification processes to ensure a safe product, no cases of viral transmission through the plasma supply have been documented since the mid-1990’s. Although the manufacturing industry has tightened its production standards, viral safety continues to be a concern among the bleeding disorders community.

In addition to the viral safety methods employed to treat or produce a given Factor VIII product, individual brands may differ in regard to storage requirements, shelf life, diluent volume, and the product’s half-life in the body. A chart comparing these products is available here for quick reference. The appropriateness of treatment with specific factor products must be evaluated on an individual basis.

All patients with Hemophilia A are at risk for the development of inhibitors, an immune response to factor products. Inhibitors are antibodies the body mistakenly forms to fight what the immune system perceives to be antigenic proteins, the factor proteins. Although some inhibitors are transient, they are difficult and expensive to treat. Treatment is called “immune tolerance therapy” and involves trying to overwhelm the immune system with excessive levels of Factor VIII. In the event that immune tolerance therapy is ineffective, treatment options are limited to Factor VIIa or a by-passing agent.