A Diagnostic Challenge: Post‐Transfusion Purpura Unmasked After Multiple Transfusions

Post‐transfusion purpura (PTP) is a rare immune‐mediated post‐transfusion reaction resulting in severe thrombocytopenia. This case presents a 52‐year‐old female with profound thrombocytopenia following multiple transfusions. PTP was not initially suspected due to her history of comorbid anti‐phospholipid antibody syndrome (APS), chemotherapy treatments, and recent heparin exposure. Her thrombocytopenia was refractory to intravenous immunoglobulin (IVIG), and she was started on plasmapheresis (PLEX) with significant improvement in platelet counts. Positive human platelet antigen (HPA)‐1a and HPA‐5b antibodies later confirmed a diagnosis of PTP. This case highlights the importance of early recognition of PTP, and treatment should not be delayed while awaiting confirmatory antibody testing.