While prophylaxis with factorreplacement improves trough levels of FVIII/FIX, there is ongoing debatewith regard to optimum values, but maintaining these above 3 IU/dl or higherhas been advocated,91 with prophylaxis now likely to include individuals with moderatedisease, particularly if associated with a bleeding phenotype of concern.For patients with hemophilia A, primary prophylaxis via subcutaneousinjection of emicizumab58 will also be an option, where licensed. This evidence concerns the gene F8 and hemophilia A.