Abstract
Recent studies have demonstrated that only 30% of patients referred for assessment of a possible bleeding tendency will eventually be diagnosed with a mild bleeding disorder (MBD) such as von Willebrand disease (VWD) or platelet function defect (PFD). Rather, most of these patients will be diagnosed with bleeding disorder of unknown cause (BDUC). There remains an important unmet need to define consensus regarding the clinical and laboratory criteria necessary for a formal BDUC diagnosis. Accumulating recent data suggest that BDUC is being diagnosed with increasing frequency. Objective assessment of bleeding phenotype using a standardized bleeding assessment tool (BAT) therefore represents a fundamental first step in the diagnosis of BDUC. Because BDUC is a diagnosis by exclusion, accurate quantification of bleeding phenotype is critical because this will be the primary determinant on which a diagnosis of BDUC is reached. Importantly, BAT scores suggest that patients with BDUC display bleeding phenotypes comparable to those seen in patients with VWD or PFD. Despite the prevalence of BDUC, diagnosis and management of these patients commonly pose significant clinical dilemmas. We consider these challenges in the context of a number of typical case studies, discuss the available evidence, and outline our approach to the management of these patients.