Emicizumab for Severe Von Willebrand Disease (VWD) and VWD/Hemophilia A

Inclusion Criteria: * Signed informed consent * Age 0 and older (infants weighing ≥3 kg) * ability to comply with protocol in investigators judgement * diagnosis of: severe VWD type 3, or VWD with VWF antigen, activity or collagen binding \</= 20 U/dl or variant VWD confirmed by genetic mutation and VWF ag, activity or CB \< 50 U/dl based on historical medical records of study site. * diagnosis of VWD/hemophilia A defined as VWF:ag, activity or CB \<50 U/dl, and mild moderate or severe hemophilia A(defined by ISTH criteria) based on historical medical records of the study site. * plan to be adherent to emicizumab prophylaxis during the study * Patient's bleeding phenotype necessitating prophylaxis per treating provider recommendations. * Patient on current prophylaxis for VWD or VWD/hemophilia A may enroll if they are currently on a non-emicizumab agent, and if it has been \> 18 months since last off-label dose of emicizumab, and are willing to discontinue current prophylaxis. * For menstruating individuals: agreement to remain abstinent (refrain from heterosexual intercourse) or use contraceptive methods that result in a failure rate of \< 1% per year during the study period. A menstruating individual is considered to be of childbearing potential if they are post-menarchal, have not reached a postmenopausal state (12 continuous months of amenorrhea with no identified cause other than menopause), and have not undergone surgical sterilization (removal of ovaries and/or uterus…