Acquired Hemophilia A Following a COVID-19 mRNA Vaccine: A Case Report

Abstract

Background: Acquired hemophilia A (AHA) develops due to autoantibodies directed against factor VIII. It can occur spontaneously or be triggered by various factors. Here, we report a case of AHA induced by the Pfizer-BioNTech COVID-19 vaccine in an older patient. Case presentation: The patient presented with multiple spontaneous bruises after receiving the Pfizer-BioNTech COVID-19 vaccine. Laboratory investigations revealed an isolated prolonged activated partial thromboplastin time (APTT) with an uncorrected mixing test. The factor VIII level was found to be low (0.6%). Additionally, the Bethesda assay evidenced the presence of an inhibitor of factor VIII. The patient was administered IV methylprednisolone and recombinant factor VIII. Then, he was maintained with oral azathioprine and prednisolone. However, the patient's condition showed no significant improvement. Thus, rituximab was administered, to which the patient responded well. Discussion and conclusion: AHA is a rare adverse effect of the Pfizer-BioNTech COVID-19 vaccine. Although the exact mechanism underlying the development of this condition following vaccination against COVID-19 remains unclear, a diagnosis of AHA should be considered if a patient without a bleeding history presents with acute-onset bleeding and an isolated prolonged APTT.