Posttransfusion purpura secondary to an alloantibody reactive with HPA-5a (Br(b))

Posttransfusion purpura with antibodies against human platelet antigen-4a following checkpoint inhibitor therapy: a case report and review of the literature

BACKGROUND

Posttransfusion purpura (PTP) is a rare condition characterized by severe thrombocytopenia following receipt of blood products. Most reported PTP cases involve alloantibodies directed against human platelet antigen (HPA)-1a. We present a case of PTP-mediated severe thrombocytopenia associated with alloantibodies directed against HPA-4a in the setting of combination checkpoint inhibitor therapy.

CASE REPORT

A 62-year-old woman with rectal melanoma that progressed on combination checkpoint inhibitors (ipilimumab and nivolumab) was admitted for abdominoperineal resection. She received multiple blood products during surgery, and between the sixth and eighth days post-surgery her platelet (PLT) count decreased from 126 × 10⁹ /L to a nadir of 1 × 10⁹ /L. She received intravenous immunoglobulin (IVIG), steroids, and romiplostim with eventual recovery of her PLT count to 50 × 10⁹ /L 20 days after surgery. She tested positive for anti-HPA-4a and was shown not to express HPA-4a, confirming a diagnosis of PTP.

CONCLUSION

Alloantibodies strongly reactive to HPA-4a were detected in this patient who received multiple blood products during abdominoperineal resection surgery. Her thrombocytopenia improved with prompt administration of IVIG, steroids, and romiplostim. PTP must always be considered in patients with acute severe thrombocytopenia after receipt of blood products, and treatment should not be delayed while awaiting laboratory confirmation. To our knowledge, this is the second reported case of PTP with antibodies against HPA-4a.

Platelet component transfusion and alloimmunization: Where do we stand?

Platelet transfusion in patients, particularly in onco-haematology, is frequent and can become chronic in some cases. Post-transfusion alloimmunization is often seen, in practice. The risk of this is significantly improved in multitransfused patients. Several classes of antigens binding on platelets (HLA and HPA) are involved and also red blood cell antigens (residual red blood cells in platelet concentrates). Platelet alloimmunization causes a poor transfusion response, refractoriness and, more rarely, post-transfusion purpura. In an alloimmunized recipient, the efficiency of platelet transfusion is based on the selection of compatible products. Significant technical progress means that several methods are currently available to ensure a good post-transfusion platelet count and a satisfactory clinical outcome for the patient.

Febrile nonhaemolytic transfusion reaction caused by antibodies against human platelet antigen 5a

Anti-human platelet antigens (HPA) alloantibodies are seldom involved in febrile nonhaemolytic reactions (FNHTRs). We describe a case in which anti-HPA-5a alloantibodies are related to an FNHTR. We studied the specificity of the alloantibodies by flow cytometry, ELISA and MACE. Typing of donors and the patient was performed by sequence-specific polymerase chain reaction. The alloantibodies were found reactive with HPA-5a antigens. The patient was HPA-5b/b, whereas the donor of the platelet apheresis involved in the FNHTR was HPA-5a/a. Despite the low frequency of anti-HPA-5a antibodies, they might be responsible for FNHTR.

Anti-HPA-1a in a case of post-transfusion purpura: binding to antigen-negative platelets detected by adsorption/elution

Post-transfusion purpura (PTP) is a rare transfusion reaction almost exclusively observed in female patients. Affected patients develop severe immune-mediated thrombocytopenia in the course of a strong anamnestic alloimmune reaction against a platelet-specific antigen. The pathophysiology of thrombocytopenia has remained elusive. Immunological analysis in the HPA-1a-alloimmunized patient described in this report revealed an antibody with features considered typical of PTP: not only was anti-HPA-1a detectable in plasma, but it could also be eluted from the patients' (alloantigen negative) platelets, and anti-HPA-1a could be detected in eluates from both antigen positive and negative test platelets, which had been incubated in the patient's serum. This is in contrast to two sera with HPA-1a alloantibodies obtained from mothers of children with neonatal alloimmmune thrombocytopenia which were strictly HPA-1a specific. It is proposed that alloantibodies with HPA-1a-like specificity explain the patient's immune thrombocytopenia. The technique described in this report is proposed for further investigation, as it might be useful for discrimination of alloantibodes in PTP and alloantibodies of transfused thrombocytopenic patients.

Efficacy of HPA-1a (PlA1)-negative platelets in a patient with post-transfusion purpura

Post-transfusion purpura (PTP) is a rare form of alloimmune thrombocytopenia that is self-limited but which carries a 10-15% mortality related to fatal hemorrhage. Immunomodulatory therapies such as plasmapheresis and intravenous immunoglobulin G (IVIg) can shorten the duration of thrombocytopenia. However, in a bleeding patient with PTP, more urgent therapy may be required. Textbooks of hematology [1-3] as well as reports in the literature [4,5] suggest that patients do not respond to platelet transfusions. We report a case of PTP in a patient homozygous for HPA-1b who suffered an intracranial hemorrhage. The patient was treated with IVIg and plasmapheresis. Because of her life-threatening bleeding, we also transfused the patient with HPA-1a-negative platelets. These transfusions consistently resulted in transient improvements in her platelet counts and may have limited the degree of intracranial bleeding. Our experience suggests that transfusion of platelets that lack the offending epitope in patients with PTP may be efficacious.

Post-transfusion purpura (PTP) and disseminated intravascular coagulation (DIC)

A 47-yr-old female with acute pancreatitis received four units of fresh frozen plasma because of subtle signs of disseminated intravascular coagulation (DIC). Seven days later, she developed severe thrombocytopenia. Serological studies demonstrated antibodies against HPA-1a together with pan-reactive antibodies against platelet glycoproteins (GPIIb-IIIa, GPIb-IX and GPIa-IIa), which was consistent with the diagnosis of PTP. The patient was treated with platelet transfusions, corticosteroids and intravenous immunoglobulin (IVIG) without permanent beneficial effect. After treatment with plasma exchange the platelet count increased to normal values.

A second case of post-transfusion purpura caused by HPA-5a antibodies: successful treatment with intravenous immunoglobulin

Post-transfusion purpura (PTP) is a rare disorder characterized by severe thrombocytopenia developing seven to 10 days following transfusion of platelet-containing blood components, in a person who was previously sensitized via transfusion or pregnancy. Although most cases of PTP are caused by alloantibodies directed against HPA-1a[(Pl(A1))], this case represents the second example of anti-HPA-5a-associated PTP. A 61-year-old female was diagnosed with acute myocardial infarction and gastrointestinal bleeding and, after receiving six units of packed red cells over 5 days, developed PTP as a result of HPA-5a [Br(b)] antibodies with severe thrombocytopenia (5000/microl). She was successfully treated with intravenous immunoglobulin (IVIG), suggesting that this is a highly effective mode of treatment for PTP, regardless of the antibody implicated.