The Malmö International Brother Study (MIBS)

Inhibitory antibodies to factor VIII develop in 10-15% of all patients with hemophilia A and in 25-30% of patients with the severe form of the disease after exposure to factor VIII concentrates. Both genetic and environmental risk factors for inhibitor development have been evaluated, but in most cases without consistent results. Among the genetic factors, an association between large rearrangements of the factor VIII and IX genes and a higher risk for inhibitors has been described. However, a majority of patients with null mutations, including the intron 22 inversion, do not develop inhibitory antibodies. It is obvious that other genetic markers influencing the immune response to replacement therapy in patients with hemophilia remain to be identified and the aim of Malmö International Brother Study (MIBS) is to characterize these factors.