Current treatment of patients with inhibitors to factor VIII.

The development of inhibitors against factor VIII or IX in hemophilic or nonhemophilic patients is a relatively rare condition, but basic and clinical studies of these inhibitors have been extremely fruitful and have led to the following: a better understanding of the structure-function relationships of the factor VIII and IX molecules; increased knowledge of the genetic defect in classic hemophilia and hemophilia B; newer insights into antibody formation against clotting factors; and an increased number of therapeutic options for the treatment of patients who have inhibitors to factor VIII or IX. The prevalence of inhibitors to factor VIII:C in the hemophiliac population of the U.S. was obtained in the NHLBI multi-center trial using 1500 patients and is estimated to be 14.5%. The vast majority of these inhibitors occurred in severely affected hemophiliacs less than twenty years of age with factor VIII:C levels of less than 0.03 u/ml. However, occasional older patients or those with F. VIII:C greater than 0.03 u/ml did develop inhibitors.