Neonatal Alloimmune Thrombocytopenia Caused by Anti-HLA-A2 Alloantibodies Determined by Luminex Single Antigen Bead Assay

Neonatal alloimmune thrombocytopenia (NAIT) occurs when maternal alloantibodies react to antigens expressed on fetal platelets, which is mainly platelet-specific alloantigen or HLA, resulting in their immune destruction. Here, we described a patient who suffered from NAIT caused by anti-HLA-A2 antibody. Sera from the mother and the newborn were screened for human platelet antigen-specific antibodies and HLA antibodies by ELISA, and HLA antibodies were detected in both of them. The antibody specificity was identified as anti-HLA-A2 by Luminex single antigen bead assay. HLA typing results showed that patient's father descended HLA-A2 antigen on the patient and the mother was HLA-A2 negative. It is most conceivable that anti-HLA-A2 alloantibody in the mother's sera crossed the placenta and subsequently caused NAIT in the case presented. The patient received platelet concentrates, oral steroid and intravenous globulin and platelet count increased to 120x10(9)/L on the 90th day of life. The Luminex single antigen bead assay used in this case is highly sensitive and specific assay to determine antibody specificity and it is faster and more convenient for routine use in clinical laboratory so that this assay could be useful to diagnose NAIT caused by HLA antibodies and treat such NAIT patients with HLA matched platelet transfusion.

A Case of Neonatal Alloimmune Thrombocytopenia dut to Anti-HLA A2

Neonatal alloimmune thrombocytopenia(NAIT) is a rare disease caused by maternal alloimmunization against fetal platelet surface antigen, which is mainly platelet specific alloantigen or human leukocyte antigen(HLA). During routine hemotology, we accidentally discovered thrombocytopenia in a female fullterm newborn admitted due to jaundice. We excluded NAIT due to human platelet alloantigen(HPA), because the HPA of the mother and baby were the same on PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism). Mother's serum was tested for lyrnphocytotoxity against 36 donor lymphocytes, and anti-HLA A2, A24 and B58 were found. HLA typing of the father and baby revealed A2 antigen which was not present on the mothers lymphocytes. The patient received concentrated platelet and intravenous globulin. Her platelet count increased to 222,000/mm from 3,000/mm on the 11th day of life. We described a case of NAIT due to anti-HLA A2 antibody with a detailed clinical feature. (J Korean Pediatr Soc 1999;43:861-865)