Long before the classification of vascular anomalies from the International Society for the Study of Vascular Anomalies (ISSVA) provided a framework to differentiate vascular anomalies, otherwise known as vascular birthmarks, it was recognized that patients with such lesions can present with acute life-threatening
hemostatic and/or thrombotic complications, as well as chronic long-standing
bleeding or thrombotic issues. Scenarios such as a rapidly growing vascular lesion with severe acute
thrombocytopenia, a visceral hemorrhagic lesion, a lesion associated with repetitive and painful superficial
thrombosis, and cases of unprovoked or post-procedural fatal
pulmonary embolism highlight the wide spectrum of manifestations of abnormal coagulation in patients with vascular anomalies. The separation of vascular anomalies into two distinct groups, vascular
tumors and
vascular malformations, was followed by the characterization that their respective coagulopathies were due to either a derangement of platelets or to a disequilibrium of the patient's coagulation/fibrinolytic process. This configuration of coagulopathies will be the foundation for this two-chapter review series. In the initial review, coagulopathies where
thrombocytopenia is the main feature will be characterized, whereas the second review will focus on
vascular malformations that have a coagulation disorder secondary to some degree of coagulation consumption and/or fibrinolytic pathway derangement.