Emicizumab in Type 3 von Willebrand Disease: Report of a Case with an Alloantibody and Literature Review.

Type 3 von Willebrand disease (VWD), the most severe form of VWD, is an inherited recessive bleeding disorder caused by the complete deficiency of von Willebrand factor (VWF). The reported prevalence is 1 per million but varies worldwide according to the frequency of consanguineous marriages. The clinical phenotype is characterized not only by mucocutaneous bleedings, but also by hemarthroses and muscle hematoma, as in patients with moderate hemophilia. Long-term prophylaxis with factor (F)VIII/VWF concentrates is recommended in patients with a history of severe and frequent bleeds. A rare complication of replacement therapy is the development of alloantibodies against VWF, with the consequences of an ineffective therapy and risk of anaphylactic reactions upon treatment. Emicizumab is the first bispecific monoclonal antibody that mimics FVIII coagulant activity and is approved for prophylaxis of bleeding in patients with inherited hemophilia A with or without inhibitors and recently also for acquired hemophilia. In this manuscript we report and discuss available data in the literature on the use of emicizumab in type 3 VWD and describe the case of a female patient with type 3 VWD with a history of alloantibodies against VWF and posttransfusion anaphylaxis, recently and successfully put on off-label prophylaxis with emicizumab.