Haemophilia Patients with Inhibitors

Most patients that have haemophilia A or B are treated by replacing their missing coagulation factor with FVIII or FIX that is either derived from plasma or developed using recombinant technology.  One of the most feared complications of the treatment of haemophilia is the development of ‘inhibitors’.  ‘Inhibitors’ are antibodies to FVIII or FIX that can develop in patients with haemophilia following replacement therapy with the missing coagulation factor. The incidence of inhibitors complicating treatment of haemophilia A and B is approximately 30% in haemophilia A and 3 to 5% in haemophilia B patients. Most of these antibodies develop during childhood. The management of haemophilia patients with inhibitors is difficult. Clinically, most inhibitors are detected when patients fail to respond to standard replacement therapy. Inhibitor levels are measured in Bethesda units (BU).