Posttransfusional Immunologic Thrombocytopenia

Abstract

A case of posttransfusional immunologic thrombocytopenia is reported in a 75-year-od PlA1-negative woman. This was the second episode of postoperative and posttransfusion thrombocytopenia in the same patient who had had only one pregnancy. Both thrombocytopenic episodes were subclinical and discovered by systematical hematologic study. A potent anti-PlA1-antibody (titer 1/128) was demonstrated by the platelet-indirect radioactive Coombs test which appeared more sensitive than other platelet immunological assays used. The very long duration of the thrombocytopenia is discussed as well as the therapeutic possibilities in such cases.

Post-transfusion purpura: case report

“…After an episode of PTP, some patients may still urgently need a transfusion. Most studies suggest that reoccurrence of PTP, though unpredictable, is unusual [19]. Such a refractory state is explained by neutralization of the subsequently infused platelet antigen by the persistent levels of isoantibody before an anamnestic reaction can occur [17].…”

Posttransfusion purpura: Two unusual cases and a literature review

“…This process presumably occurs through binding of soluble platelet antigens in the transfused blood product to the intact platelets of the affected patient, and is supported by in vitro data demonstrating that soluble PLA' antigen is present in stored blood, and that incubation of PLA'-negative platelets in stored plasma leads to their assumption of a PLA'-positive phenotype [ 13,3 11. However, this mechanism, though attractive, fails to explain the observation that thrombocytopenia has been reported to persist for more than 1 month in some individuals affected with PTP [20,32]. Another hypothesis suggests that exposure to foreign platelets induces the formation of an autoantibody reactive with autologous platelets [33,34].…”

Alloantibodies and Platelet Destruction

“…10 The thrombocytopenia has occasionally been reported to persist for months. 57 ' 78 The degree of thrombocytopenia varies from subclinical 78 (noted only in retrospect) to severe (associated with bleeding). The first cases were all in females but male patients have now been reported.…”

“…93 The initial exposure may have been many years previously. 46,78 Two cases of PTP have been described in patients in whom there has been no previous sensitizing event. 59,72 Although most patients with PTP have normal or marginally increased marrow megakaryocytes, 10,22,46,93 cases associated with failure of megakaryocytic maturation and transient marrow failure have been reported.…”

“…44,73 Recurrences have been reported to occur years after the initial episode. 78 Perhaps anti-P1 A1 is not the only cause of PTP. Perhaps P1 A1 -positive and P1 A1 -negative platelets share closely related antigenic determinants and the antibody elicited by P1 A1 -positive platelets is able to cross-react with a determinant on P1 A1 -negative platelets.…”