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 ...
or
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 transfusi ...
that occurs when the body has produced
alloantibodies 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 an ...
, 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.
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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 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 dem ...
therapy is the primary treatment. Additionally, PTP is a
American Society for ApheresisCategory III indication for plasmapheresis.
See also
*
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 ...
*
Neonatal alloimmune thrombocytopenia
Neonatal alloimmune thrombocytopenia (NAITP, NAIT, NATP or NAT) is a disease that affects babies in which the platelet count is decreased because the mother's immune system attacks her fetus' or newborn's platelets. A low platelet count increases ...
References
Transfusion medicine
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Transfusion reactions