Post-transfusion purpura (PTP) is an adverse reaction to a blood transfusion or platelet transfusion that occurs when the body produces alloantibodies to the introduced platelets' antigens. These alloantibodies destroy the patient's platelets leading to thrombocytopenia, a rapid decline in platelet count.[1] PTP usually presents 5–12 days after transfusion, and is a potentially fatal condition.
PTP is rare, but usually occurs in women who have had multiple pregnancies or in men who have undergone previous transfusions. The precise mechanism leading to PTP is unknown, but it most commonly occurs in individuals whose platelets lack the HPA-1a antigen (old name: PLA1) are transfused platelets that do contain the HPA-1a antigen. The patient develops antibodies to the HPA-1a antigen leading to platelet destruction. It is unclear why alloantibodies attack the patient's own, as well as the introduced platelets.[2] It is usually self-limiting, but IV IgG therapy is the primary treatment.[3] Plasmapheresis is also an option for treatment.[4]