The differential diagnosis of impaired primary hemostasis (summarized in Table 2) includes von Willebrand disease, acquired platelet dysfunction (e.g., use of non-steroidal anti-inflammatory drugs), inherited platelet dysfunction [e.g., Glanzmann thrombasthenia (GT), Bernard-Soulier syndrome (BSS), ADP receptor defect, and gray platelet syndrome], and vascular anomaly (e.g., Ehlers-Danlos syndrome) (37). Here, P2RY1 is linked to platelet-type von Willebrand disease.