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Among patients with hemophilia A (factor VIII deficiency), blacks are twice as likely as whites to develop alloantibodies that inhibit factor VIII replacement products. This condition occurs in as many as 25% of patients and is associated with intensive therapy, hemophilia severity, and early exposure to clotting factor concentrates. To determine underlying causes of this racial discrepancy, investigators studied factor VIII protein composition in 78 black patients known to produce these inhibitory antibodies.
Sequencing of the F8 gene revealed four single nucleotide polymorphisms whose haplotypes encoded six distinct factor VIII proteins. Two of these polymorphisms were associated with the nonfunctional B domain of the molecule, which does …