P2Y12 defect (Orphanet_36355) is a rare hemorrhagic disorder characterized by mild to moderate bleeding diathesis with easy bruising, mucosal bleedings, and excessive post-operative hemorrhage due to defect of the platelet P2Y12 receptor resulting in selective impairment of platelet responses to adenosine diphosphate. Also known as: ADP platelet receptor P2Y12 defect.