Post-transfusion purpura

[1] PTP usually presents 5–12 days after transfusion, and is a potentially fatal condition in rare cases.

[2] PTP is rare, but usually occurs in women who have had multiple pregnancies or in people 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).

It is unclear why alloantibodies attack the patient's own, as well as any transfused allogeneic random donor platelets.

[4] Additionally, PTP is an American Society for Apheresis Category III indication for plasmapheresis.