Bleeding Disorder of Unknown Cause

The purpose of the Bleeding Disorder of Unknown Cause in the Netherlands study (BDUC-iN) is to learn more about unexplained bleeding in individuals with a bleeding disorder of unknown cause (BDUC). The study aims to better understand why these individuals have increased bleeding and how it affects their health and daily life. The main questions of this study are: 1. What are the mechanisms underlying the bleeding tendency in BDUC? 2. How do bleeding symptoms affect patients' daily functioning and overall health-related quality of life? 3. How is care delivered to individuals with BDUC, and how can this be improved? Participants with increased bleeding tendency who remain undiagnosed after standard coagulation testing and are consequently classified as having BDUC will be enrolled across the Hemophilia treatment centers in the Netherlands. Participants will undergo blood sampling for advanced hemostasis testing and genetic analysis. In addition, participants will complete validated questionnaires to assess bleeding symptoms and health-related quality of life. Participants will be followed longitudinally to evaluate how bleeding symptoms affect daily activities, medical procedures, and overall health-related quality of life.