Acquired Hemophilia A Secondary to an Immune Checkpoint Inhibitor: A Case Report.

We report a case of a patient with extensive-stage SCLC who developed acquired hemophilia A during maintenance atezolizumab therapy. The patient initially presented with asymptomatic anemia, a prolonged acquired prothrombin time, and factor VIII (FVIII) deficiency. Acquired FVIII autoantibodies were detected, confirming the diagnosis of acquired hemophilia.