Inclusion Criteria for patients:  Adult patients who were diagnosed with "low VWF" and have VWF:Ag and/or VWF:RCo between 30-50 IU/dL with a ratio of VWF:RCo/VWF:Ag > 0.6. Subjects who have given informed consent to participate in the study according to the Declaration of Helsinki  Inclusion Criteria for healthy controls:  Healthy subjects with no known bleeding disorders and with negative thrombophilia screening results Subjects who have given informed consent to participate in the study according to the Declaration of Helsinki  Exclusion Criteria:  Pregnant women Patients with acquired von Willebrand disease syndrome