Washington Manual of Medical Therapeutics
Post-transfusion Purpura
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General Principles
Definition
Post-transfusion purpura (PTP), a rare syndrome characterized by the formation of alloantibodies against platelet antigens, most commonly HPA-1a, follows blood component transfusion and causes severe thrombocytopenia.
Epidemiology
PTP has an incidence of 1 in 50,000 to 100,000 blood transfusions, although approximately 2% of the population has a potential risk for PTP based on the frequency of HPA-1b/1b.
Etiology
Glycoprotein (GP) IIIa has a polymorphic epitope called HPA-1a/b, the antigen most commonly involved in PTP. PTP typically occurs in HPA-1a/1b–negative multiparous women or previously transfused patients when re-exposed to HPA-1a by transfusion. An amnestic response produces alloantibodies to the HPA-1a, which appear to also recognize the patient’s HPA-1a–negative platelets and cause thrombocytopenia via platelet destruction.
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General Principles
Definition
Post-transfusion purpura (PTP), a rare syndrome characterized by the formation of alloantibodies against platelet antigens, most commonly HPA-1a, follows blood component transfusion and causes severe thrombocytopenia.
Epidemiology
PTP has an incidence of 1 in 50,000 to 100,000 blood transfusions, although approximately 2% of the population has a potential risk for PTP based on the frequency of HPA-1b/1b.
Etiology
Glycoprotein (GP) IIIa has a polymorphic epitope called HPA-1a/b, the antigen most commonly involved in PTP. PTP typically occurs in HPA-1a/1b–negative multiparous women or previously transfused patients when re-exposed to HPA-1a by transfusion. An amnestic response produces alloantibodies to the HPA-1a, which appear to also recognize the patient’s HPA-1a–negative platelets and cause thrombocytopenia via platelet destruction.
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