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Inhibitors

Some people with hemophilia develop antibodies after they have received factor VIII concentrate. These antibodies are referred to as inhibitors.

What is an inhibitor?

An inhibitor is an antibody produced by the body’s immune system that identifies factor VIII concentrate as a foreign substance and attacks it, neutralizing its activity and making it ineffective in stopping bleeding.¹ Up to 30% of individuals with severe hemophilia A—those with factor VIII levels less than 1% of normal—develop inhibitors.²

An inhibitor can develop only after a person has been treated with replacement clotting factor. Most inhibitors occur early in life, usually within the first 50 days of treatment with replacement clotting factor.³

What is the impact of an inhibitor?

Patients with inhibitors do not bleed more frequently than other hemophilia patients, but their bleeds are more difficult to manage because they do not always respond to standard treatment.¹ As a result, inhibitor patients may develop serious complications,^4-6 such as bleeding inside a joint, called hemarthrosis. Joint bleeding usually occurs in the knees, elbows, and ankles, and it can be very painful.⁷ Repeated bleeding into a joint may cause permanent joint damage, termed arthropathy, that results in a loss of normal joint function and, often, visible deformity.⁸

Are you at risk?

Anyone with hemophilia can develop an inhibitor. However, there are some factors that may increase your risk. These include:

• Major changes, called mutations, in the factor VIII gene⁹
• A family history of inhibitors¹⁰
• African heritage¹¹

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1. Kasper CK. Diagnosis and management of inhibitors to factors VIII and IX. An introductory discussion for physicians. Treatment of Hemophilia; September 2004, no.34.
2. Brackmann HH, Wallny T. Immune tolerance: high-dose regimen. In: Rodriguez-Merchan E.C. LCA, ed. Inhibitors in Patients With Hemophilia. Oxford, England: Blackwell Science, Ltd.; 2002:45-48.
3. DiMichele D. Inhibitors: resolving diagnostic and therapeutic dilemmas. Haemophilia. 2002;8:280-287.
4. Ingerslev J, Freidman D, Gastineau D, et al. Major surgery in haemophilic patients with inhibitors using recombinant factor VIIa. Haemostasis. 1996;26 Suppl 1:118-123.
5. Brackmann HH, Schwaab R, Effenberger W, Hess L, Hanfland P, Oldenburg J. Antibodies to factor VIII in hemophilia A patients. Vox Sang. 2000;78 Suppl 2:187-190.
6. Lusher JM. Inhibitor antibodies to factor VIII and factor IX: management. Semin Thromb Hemost. 2000;26:179-188.
7. Silva M, Luck JV, Jr., Llinás A. Treatment of Hemophilia Monograph Series [No. 33 Available at: http://www.wfh.org/2/docs/Publications/Musculoskeletal_Physiotherapy/
   TOH-33_English_Synovectomy.pdf. Accessed May 19, 2006.; 2006.
8. Leissinger CA. Use of prothrombin complex concentrates and activated prothrombin complex concentrates as prophylactic therapy in haemophilia patients with inhibitors. Haemophilia. 1999;5(suppl 3):25-32.
9. Oldenburg J. Neutralizing antibodies to FVIII. Risk factors for inhibitor development. Baxter Scientific Series, No. 2; 2004; Westlake Village, Calif: Baxter Healthcare Corp
10. Astermark J, Berntorp E, White GC, Kroner BL. The Malmo International Brother Study (MIBS): further support for genetic predisposition to inhibitor development in hemophilia patients. Haemophilia. 2001;7:267-272.
11. Lusher J, Abildgaard C, Arkin S, et al. Human recombinant DNA-derived antihemophilic factor in the treatment of previously untreated patients with hemophilia A: final report on a hallmark clinical investigation. J Thromb Haemost. 2004;2:574-583.

*Note: thereforyou.com does not recommend a particular treatment for specific individuals and recommends that you consult your treatment center or physician before pursuing any course of treatment.