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 1980s and
early 1990s, 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-1990s. 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
products 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
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