Post Transfusion Purpura (PTP) is a rare but serious complication of transfusion in which thrombocytopaenia and purpura (bleeding underneath the skin) develops 5 – 10 days post transfusions as a result of destruction of transfused as well as autologous platelets. PTP is more common in multiparous females due to previous sensitisation during pregnancy and is due to HPA antibodies boosted by the transfusion. Studies have also shown that pan specific HPA antibodies are present during the thrombocytopaenic phase and these transient antibodies are probably responsible for the autologous platelet destruction.

H&I laboratory investigations for PTP include confirmation of circulating HPA antibodies in the patient, typically by the flowcytometric Platelet Immunofluorescence Test (PIFT) and/or the Monoclonal Antibody Specific Immobilisation of Platelet Antigens (MAIPA) test.

PTP is treated with IVIg, with plasmapheresis as a second line treatment. Do not transfuse with more platelets as this would trigger more HPA antibodies.