Post-transfusion purpura (PTP) is a delayed adverse reaction to a

blood transfusion Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...

platelet transfusion Platelet transfusion, also known as platelet concentrate, is used to prevent or treat bleeding in people with either a low platelet count or poor platelet function. Often this occurs in people receiving cancer chemotherapy. Preventive transfus ...

that occurs when the body has produced

alloantibodies Alloimmunity (sometimes called isoimmunity) is an immune response to nonself antigens from members of the same species, which are called alloantigens or isoantigens. Two major types of alloantigens are blood group antigens and histocompatibility an ...

to the allogeneic transfused platelets'

antigens In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...

. These alloantibodies destroy the patient's platelets leading to

thrombocytopenia Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients a ...

, a rapid decline in platelet count. PTP usually presents 5–12 days after transfusion, and is a potentially fatal condition in rare cases. Approximately 85% of cases occur in women. __TOC__

Mechanism

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 Human platelet antigens (HPA) are polymorphisms in platelet antigens. These can stimulate production of alloantibodies (that is, antibodies against other people's antigens) in recipients of transfused platelets from donors with different HPAs. T ...

antigen (old name: PL^A1). The patient develops antibodies to the HPA-1a antigen leading to platelet destruction. In some cases, HPA-5b has also been implicated. It is unclear why alloantibodies attack the patient's own, as well as any transfused allogeneic random donor platelets. Probable explanation for this is that the recipient's platelets acquire the phenotype of donor's platelet by binding of the soluble antigens from the donor onto the recipient's platelet.

Treatment

Symptoms are usually sudden in onset and self-limiting, most often resolving within 2 weeks.

IVIG Immunoglobulin therapy is the use of a mixture of antibodies (normal human immunoglobulin or NHIG) to treat several health conditions. These conditions include primary immunodeficiency, immune thrombocytopenic purpura, chronic inflammatory ...

therapy is the primary treatment. Additionally, PTP is a
American Society for Apheresis
Category III indication for plasmapheresis.

References

Transfusion medicine {{treatment-stub Transfusion reactions

Mechanism

Treatment

See also

References