Existing data support the concept that a genetic predisposition for inhibitor development exists. The aim of the Malmö International Brother Study (MIBS) is to evaluate genetic factors associated with the development of inhibitory antibodies in patients with hemophilia.

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.

Inclusion Criteria:

-Mild, moderate or severe hemophilia A or B and one or more brothers with mild, moderate or severe hemophilia A or B

Exclusion Criteria:

-Absence of sufficient information to classify inhibitor status