PTP is caused by platelet-specific antibodies in a patient who has been previously exposed to platelet antigens through pregnancy or transfusion. The most frequently identified antibody is Anti-PLA1, which reacts with platelet antigen HPA-1a. The platelet antibody binds to the platelet surface, which allows for extravascular removal through the liver or the spleen. The patient's own platelets are destroyed as well, thus aggravating the thrombocytopenia.
Three theories are suggested regarding the destruction of autologous platelets. One suggests that immune complexes bind to the platelets through the Fc receptor and cause destruction. The second theory proposes that the patient's platelets absorb a soluble platelet antigen from the donor plasma. The third hypothesis, which has the most support, states that the platelet alloantibody has autoreactivity that develops when the patient is exposed to the foreign platelet antigen.
Platelet transfusion is NOT a treatment option. Steroids, whole blood exchange, and plasma exchange are accepted options for treatment. According to the AABB, intravenous IgG (IVIG) is the treatment of choice. Most patients will respond to treatment within several hours to four days. PTP does not usually re-occur but it is recommended that patient's with a previous reaction be transfused with antigen-matched components. Autologous donations or directed donations from antigen-matched family members may be the best sources of blood. PTP has been known to occur even after the transfusion of deglycerolized rejuvenated or washed red cells, so these processes do not prevent a reaction.