Understanding Hemophilia Hemophilia with Inhibitors
Some people with hemophilia develop antibodies after they have received factor 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 concentrate as a foreign substance
- Attacks factor
- Neutralizes factor activity
- Makes factor ineffective or less effective in stopping bleeding.1
Approximately 30% of individuals with severe hemophilia A—those with factor VIII levels less than 1% of normal—develop inhibitors.2 Inhibitors are more common in people with severe hemophilia due to the need for more frequent infusions. However, only about 3-5% of people with severe hemophilia B develop an inhibitor, which is a much lower incidence than in severe hemophilia A.3
An inhibitor can develop only after a person with congenital hemophilia 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.4
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 have an increased risk of developing complications such as joint damage.5 Initially, a joint bleed or hemarthrosis occurs. Joint bleeding usually occurs in the knees, elbows, and ankles, and it can be very painful.6 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.6
Who Is At Risk?
Anyone with hemophilia can develop an inhibitor. However, there are some factors that may increase your risk. These include:
- Major genetic changes, called mutations, in the factor VIII or IX gene7
- A family history of inhibitors8
- African heritage8
- Hemophilia severity1
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.
References
- Kasper CK. Diagnosis and management of inhibitors to factors VIII and IX. An introductory discussion for physicians. Treatment of Hemophilia. № 34. Montréal, Canada: World Federation of Hemophilia; Sept. 2004.
- Scharrer I, Bray GL, Neutzling O. Incidence of inhibitors in haemophilia A patients: a review of recent studies of recombinant and plasma-derived factor VIII concentrates. Haemophilia 1999; 5(3): 145-154.
- Factor IX Deficiency. National Hemophilia Foundation website. http://www.hemophilia.org/NHFWeb/MainPgs/MainNHF.aspx?menuid=181&contentid=46&rptname=bleeding. Accessed January 21, 2013
- DiMichele D. Inhibitors: resolving diagnostic and therapeutic dilemmas. Haemophilia. 2002;8:280-287.
- 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.
- Silva M, Luck JV, Jr., Llinás A. Chronic Hemophilic Synovitis: The Role Of Radiosynovectomy. Treatment of Hemophilia. No.33. Montréal, Canada: World Federation of Hemophilia; April. 2004.
- Schwaab R, Brackmann HH, Meyer C, Seehafer J, Kirchgesser M, Haack A, Olek K, Tuddenham EG, Oldenburg J. Haemophilia A: mutation type determines risk of inhibitor formation. Thrombosis and Haemostasis. 1995 Dec; 74 (6): 1402-6.
- 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.
