Aortic thrombosis and acute limb ischemia after ChAdOx1 nCov-19 (Oxford-AstraZeneca) vaccination: a case of vaccine-induced thrombocytopenia and thrombosis (VITT).

INTRODUCTION: Vaccine-induced thrombocytopenia and thrombosis (VITT) is a rare but devastating adverse event associated with the ChAdOx1 nCoV-19 (Oxford-AstraZeneca) adenoviral vaccine against the Severe Acute Respiratory Syndrome CoronaVirus-2 (SARS-CoV-2). METHODS: A 49-year-old man presented to the emergency department with acute right limb ischemia (Rutherford IIB) nine days after his ChAdOx1 nCoV-19 (Oxford-AstraZeneca) vaccination. CT angiography revealed significant aortic thrombosis and right femoral artery occlusion. Severe thrombocytopenia (platelet count of 23 × 103/µL), promptly elevated D-dimers (37937 ng/mL) and a reduced fibrinogen level (176 mg/dL) were remarkable. ELISA testing for anti-PF4 antibodies confirmed the diagnosis of VITT. RESULTS: An emergency revascularization of the right leg was provided via thrombectomy. High-dose intravenous immunoglobulins were administered whereafter the platelet count restored gradually. Therapeutic anticoagulation was progressively started. The postoperative course was uneventful and follow-up imaging after four weeks showed an almost complete resolution of the significant aortic thrombosis. CONCLUSION: Early recognition and appropriate counseling of VITT is advocated to pursue a good clinical outcome. Our patient presenting with severe aortic thrombosis and acute limb ischemia was successfully treated by a vascular thrombectomy along with intravenous immunoglobulins and anticoagulation therapy as the mainstay therapy.

Detection of Platelet-Activating Antibodies Associated with Vaccine-Induced Thrombotic Thrombocytopenia by Flow Cytometry: An Italian Experience.

Rare cases of thrombocytopenia and thrombosis after anti-COVID-19 adenovirus-associated mRNA vaccines (VITT) due to platelet-activating anti-platelet-factor 4 (PF4)/polyanion antibodies have been reported. VITT laboratory diagnosis, similarly to heparin-induced thrombocytopenia (HIT) diagnosis, requires immunoassays for anti-PF4/polyanion antibodies identification, such as ELISA assays and platelet-activating functional tests, such as heparin-induced platelet activation test (HIPA), to confirm their pathogenicity. We compared the flow cytometry (FC) measurement of platelet p-selectin exposure to the gold standard functional test HIPA for diagnosis confirmation in 13 patients with a clinical VITT syndrome (6M/7F; median age 56 (33-78)) who resulted positive to anti-PF4/polyanion antibodies ELISA assays (12/13). FC and HIPA similarly identified three different patterns: (1) a typical non-heparin-dependent VITT pattern (seven and six patients by FC and HIPA, respectively); (2) low/no platelet activation in patients under IvIg therapy (five out of five and two out of four patients by FC and HIPA, respectively); (3) a HIT pattern. Antibodies investigated by FC became negative after 7, 17, and 24 days of therapy in three patients. FC measurement of P-selectin exposure was as sensitive as HIPA but simpler to detect anti-PF4/polyanion antibodies in VITT patients. FC could reliably discriminate VITT from HIT, thus helping for the choice of the anticoagulant.