Passive alloimmune thrombocytopenia_anti-HPA 1a

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MPHO Type: 
Estimated frequency: 
Passive alloimmune thrombocytopenia is a very rare but serious complicaction of blood transfusion. Approximately twenty cases have been described so far, most of them associated with female blood donors with a history of pregnancy. The small number of cases reported suggests that this complication is under-recognised. In this article the authors describe a rare example of passive anti-HPA antibody transfer from the plasma of a male blood donor causing acute thrombocytopenia.
Time to detection: 
A 58-year-old renal transplant recipient was admitted to hospital for investigation and management of acute kidney injury. She had received a deceased donor kidney transplant 13 years before for end-stage renal failure attributed to glomerulonephritis. A renal biopsy was consistent with antibody-mediated rejection. She was commenced on plasma exchange, intravenous immunoglobulin and antibiotics. A new thrombocytopenia was observed on routine blood tests 24h after the third day of plasma exchange, with a platelet count of 7x109/L (previous normal).
Alerting signals, symptoms, evidence of occurrence: 
In addition to thrombocytopenia, she had a large haematoma over the site of a subcutaneous heparin injection without any other bleeding sites.
Demonstration of imputability or root cause: 
Testing for heparin-induced thrombocytopenia did not proceed given a low pre-test probability (4T score of 3: low risk). The time frame did not match the commencement of antibiotics, and the thrombocytopenia improved without discontinuation of the drug. Testing of the fresh frozen plasma (FFP) donors with a monoclonal antibody-specific immobilisation of platelet antigens (MAIPA) assay demonstrated that one of the five donors has anti-HPA-1a antibodies. The donor was genotyped and found to have a HPA-1bb genotype. The recipient also had a genotype performed and was found to be HPA-1aa. Anti-HPA-1a antibodies were not detected in the patient's serum. On review, the donor was noted to have provided plasma for 17 other patients. Treating clinicians were notified of the adverse transfusion reaction. Five clinicians reported post-transfusion falls in platelet count. Four were attributed to alternate causes, and one was considered a possible unrecognised adverse transfusion reaction. The detection of anti-HPA1a antibodies in the donor in conjunction with HPA-1aa recipient genotyping and a precipitous drop in the platelet count following transfusion is considered diagnostic in this case.
Imputability grade: 
3 Definite/Certain/Proven
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Reference attachment: 
Suggest references: 
1) Thrombocytopenia secondary to passive transfer of anti-HPA 1a antibodies from male donor plasma. F. Swain, S. Baidya, et al. Transfusion Medicine, 2018 2) Post-transfusion purpura secondary to passive transfer of anti-Pl1 by blood transfusion. P.J. Ballen, N.A. Buskard, F. Decary and P. Dubroff. Br J Hematol, 1987 3) Consequences of transfusion of platelet antibody: a case report and literature review (1981-1989). K. Pavenski, K.E. Webert and M. Goldman. Transfusion 2008
Expert comments for publication: 
The case highlights that this complication can still occur (despite the use of male-only clinical plasma and apheresis platelets) and should remain in the differential diagnosis for acute thrombocytopenia in the context of recent transfusion of plasma-containing blood components.