Acute-type acquired hemophilia A after COVID-19 mRNA vaccine administration: A new disease entity?

Acquired hemophilia A (AHA) is a rare autoimmune bleeding disorder. Various autoimmune diseases, including AHA, have been reported to occur after the administration of mRNA COVID-19 vaccines. However, the characteristics of these AHA cases remain unclear. We report a case in which AHA arose in a young patient after the administration of an mRNA COVID-19 vaccine, but improved rapidly. The patient's factor VIII (FVIII) inhibitor titer spontaneously decreased to less than half of that seen at diagnosis. One week after the initial immunosuppressive therapy, the FVIII inhibitor had disappeared. Our case suggests that AHA that arises in young patients after COVID-19 vaccination may resolve spontaneously, and the levels of FVIII inhibitors may decrease more rapidly in such cases than in idiopathic AHA. Unlike for immune thrombocytopenic purpura (ITP), no acute type of AHA has been recognized. This case suggests that just as there is an acute type of ITP that develops in children/after vaccination, there may be an acute type of AHA that arises in young patients that receive mRNA COVID-19 vaccines.