A case of an adolescent with antiphospholipid syndrome and persistently high PF4 levels with recurrent late thrombotic complications after mRNA SARS-CoV-2 vaccine

Abstract

Background: Anti-phospholipid syndrome (APS) is an autoimmune disease causing arteriovenous thrombosis in the presence of antiphospholipid antibodies. Pediatric APS develops at less than 18 years of age. Various factors exacerbate pediatric APS. Herein, we report a case of a patient with pediatric APS who developed deep vein thrombosis (DVT) 6 months after second vaccination due to persistent platelet activation caused by exacerbation of APS after administration of the BNT162b2 vaccine. Case presentation: A 17-year-old female developed DVT at the age of 6 years. She had no family history of thrombophilia. The thrombus was found in the right common iliac vein to the inferior vena cava, with concomitant left pulmonary infarction. After treatment with warfarin, the pulmonary infarction resolved, but the thrombus from the right common iliac vein to the inferior vena cava became organized and remained until now. The patient was treated with anticoagulants for 6 years after the onset of DVT and then without treatment for 5 years without recurrence of thrombosis. The first dose of the BNT162b2 vaccine was administered 1 week before a routine outpatient visit. However, PF4 levels were elevated after vaccination and even after 5 months, but without thrombotic symptoms. A second dose of the BNT162b2 vaccine was administered; 6 months later, the patient developed recurrent deep vein thromboembolism in the right common iliac vein and was treated with direct oral anticoagulants. Conclusions: The persistence of high PF4 levels after vaccination in a patient with DVT may indicate an association between the vaccine and DVT due to the exacerbation of APS by the BNT162b2 vaccine. After vaccination of patients with a predisposition to thrombosis, the state of coagulation, including platelet activation markers, should be monitored to prevent the development of DVT.