key: cord-0757822-inylhyr7 authors: Long, Brit; Bridwell, Rachel; Gottlieb, Michael title: Vaccine-induced immune thrombotic thrombocytopenia: why, what, who, and how?() date: 2022-04-25 journal: Am J Emerg Med DOI: 10.1016/j.ajem.2022.04.020 sha: c267986758b2f1f2dcd953c395b93d6e191eaa58 doc_id: 757822 cord_uid: inylhyr7 nan thrombosis. 2,3 This causes a consumptive coagulopathy leading to thrombocytopenia, elevated D-dimer levels, and hypofibrinogenemia. Initial reports found high levels of IgG antibodies against platelet factor 4 (PF4) in patients with VITT. [4] [5] [6] [7] Thus, this pathophysiology resembles heparin-induced thrombocytopenia (HIT), but in classic HIT, antibodies recognize the complex formed between PF4 (positively charged) and heparin (negatively charged). 8 The complete pathophysiology of VITT is not completely understood, specifically how adenovirus vector vaccines function as a trigger of the condition, but components of these vector vaccines may interact with PF4 and result in VITT. 2,9,10 These components may include the viral capsid, edetic acid or other human proteins, spike proteins, and others. 9, 10 The clinical characteristics of VITT and HIT overlap significantly. In VITT, thrombosis may include deep vein thrombosis and pulmonary embolism, as well as atypical sites (e.g., splanchnic vein thrombosis, cerebral vein thrombosis, etc.) and arterial thrombosis. 1-3 VITT occurs almost exclusively in those receiving the Oxford-AstraZeneca or Johnson & Pathologic Antibodies to Platelet Factor 4 after ChAdOx1 nCoV-19 Vaccination Thrombotic Thrombocytopenia after ChAdOx1 nCov-19 Vaccination Thrombosis and Thrombocytopenia after ChAdOx1 nCoV-19 Vaccination US Case Reports of Cerebral Venous Sinus Thrombosis With Thrombocytopenia After Ad26.COV2.S Vaccination Spontaneous HIT syndrome: Knee replacement, infection, and parallels with vaccine-induced immune thrombotic thrombocytopenia Insights in ChAdOx1 nCoV-19 vaccineinduced immune thrombotic thrombocytopenia Mechanisms of Immunothrombosis in