Abstract
A 73-year-old Japanese man with chronic kidney disease had no history of abnormal clotting or bleeding. Six days after receiving his third dose of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine (BNT162b2; Pfizer/BioNTech), blood tests showed a marked prolongation of the prothrombin time-international normalised ratio and activated partial thromboplastin time, as well as a decrease in factor V (FV) activity. Three months later, he required dialysis owing to worsening heart and renal failure. After supplementation with FV, a flexible double-lumen catheter was inserted, and haemodialysis was initiated without the use of anticoagulants. The patient was found to be positive for FV inhibitors and was diagnosed with autoimmune acquired factor V deficiency (AiFVD). AiFVD is a rare autoimmune disease in which factor V inhibitors decrease FV activity. The patient did not undergo immunosuppressive therapy because he did not have severe bleeding symptoms, and he is currently able to continue dialysis without causing fatal bleeding. FV inhibitors can be induced by bovine thrombin, surgery, and infection, but have also been detected after SARS-CoV-2 infection. The development of various acquired coagulation factor inhibitors has been reported after SARS-CoV-2 infection or vaccination, but there have been no reports of AiFVD due to SARS-CoV-2 vaccination. To the best of our knowledge, this is the first report of AiFVD probably associated with SARS-CoV-2 vaccination. Although AiFVD is rare, physicians should be aware of its possibility after SARS-CoV-2 vaccination.