Effects of Emicizumab vs. Factor VIII Prophylaxis on Joint and Bone Health in Severe Hemophilia A

The investigators propose to study longitudinal joint and bone density changes in patients with severe Hemophilia A. Per current standard of care, most patients are on prophylactic FVIII replacement therapy intravenously several times weekly with a goal of keeping the trough \>1% FVIII. Recent phase 3 data suggest superior bleed protection with emicizumab prophylaxis every 1-2 weeks. It is the purpose of this study to longitudinally assess joint health and bone density over 3 years and to compare the effect of routine factor VIII prophylaxis with emicizumab prophylaxis.