Uncommon Presentation of Post-Transfusion Purpura in an Elderly Male: A Case Report and Unique Alloantibody Identification.

BACKGROUND Post-transfusion purpura (PTP) is a rare delayed adverse event characterized by severe thrombocytopenia associated with mucosal bleeding and purpura. PTP is associated with the development of alloantibodies to human platelet antigens (HPAs) and should be distinguished from other thrombocytopenic syndromes. This report is of a 69-year-old man with refractory cardiogenic shock and thrombocytopenia 4 days following blood transfusion, diagnosed with post-transfusion purpura. CASE REPORT A 69-year-old man was admitted to a tertiary medical center with refractory cardiogenic shock. Four days after he received 1 unit of packed red blood cells, his platelet count plummeted from 147 K/uL to <2 K/uL within hours, associated with delayed presentation of notable hematuria and femoral catheter oozing. An extensive thrombocytopenia work-up, including an initial platelet antibody screen, was unrevealing. The patient was treated with supportive transfusions, dexamethasone, and intravenous immunoglobulin, with rapid platelet recovery. Post-transfusion purpura panel testing later identified anti-human platelet antigen-5b antibodies, confirming the diagnosis. CONCLUSIONS This report presents an unusual course and presentation of post-transfusion purpura in an elderly man. Unusual features of this case include male sex, hyper-acuity of thrombocytopenia, lack of prior transfusions, exam findings, identification of a less common alloantibody, and negative initial platelet antigen screening. This report highlights the importance of monitoring patients for post-transfusion adverse events. Although PTP is rare, rapid diagnosis and management are required to control this potentially life-threatening condition.