Clotting factor replacement therapy is the main treatment for children with hemophilia. This treatment, which is given through a vein with intravenous (IV) infusion or with a small butterfly needle, can increase clotting factor levels and reduce the severity and frequency of bleeding episodes and other symptoms, such as pain and swelling. Clotting factor replacement therapy is also commonly used to prevent complications of severe hemophilia, such as recurrent bleeding into the joints.
Children with hemophilia type B, who are missing clotting factor IX, need infusions twice a week. Children with hemophilia A need infusions of factor VIII three times a week, because the protein does not last as long in the body as factor IX. Researchers are working to develop longer-acting clotting factors, which may reduce the frequency of treatment.
Clotting factor replacement therapy is initially done in the doctor’s office and takes only a few minutes. When a family is ready, the NYU Langone team sends visiting nurses to perform these infusions in your home. Doctors and nurse practitioners at NYU Langone and the home nursing staff can teach parents how to give their child infusions, so that the nurse visits are no longer necessary. Eventually, you or a nurse can teach your child how to perform infusions and learn to manage the condition during adolescence and adulthood.
Immune Tolerance Test
Up to 30 percent of people with severe hemophilia type A and less than 3 percent of people with hemophilia type B develop an immune response, or antibodies, to the clotting factors used in replacement therapy. These antibodies, also called inhibitors, recognize the clotting factor as a foreign substance that needs to be destroyed, making treatment less effective. The risk of developing these antibodies decreases after your child has used clotting factor replacement therapy for a long period of time.
Before beginning clotting factor replacement therapy, the doctor may perform a blood test to determine if your child has antibodies to clotting factor replacement therapy. If he or she has these antibodies, the test may be repeated to determine how long the clotting factor replacement survives in the presence of these antibodies.
The doctor sends the blood sample to a laboratory that specializes in testing for clotting factor inhibitors. Results are available within 24 hours. If your child’s immune response is mild—meaning he or she makes some antibodies to the clotting factor—the doctor may increase the dose to overwhelm the immune system, increasing the therapy’s effectiveness. If your child develops a high number of antibodies to the clotting factor, the doctor may prescribe a different type of clotting factor.
Immune Tolerance Therapy
A doctor may use immune tolerance therapy, also known as immune tolerance induction, to eliminate antibodies to a clotting factor. In one approach, a doctor gives large doses of the clotting factor to your child, by itself or in combination with medications such as corticosteroids and rituximab, or Rituxan®, which suppress the immune system, for months. A child may receive immune tolerance therapy for several years.
Immune tolerance therapy is effective for many children who have an immune reaction to clotting factor. It is more likely to succeed in children with fewer antibodies and when treatment begins shortly after an immune response is detected. The main side effects are an increased risk of infections from immunosuppressant medications and pain and bruising at the injection site.