A Case of Neonatal Alloimmune Thrombocytopenia Due to Anti-HLA A29 Antibody

Abstract

Neonatal alloimmune thrombocytopenia (NAIT) occurs when a mother is immunized against fetal platelet-specific alloantigen and rarely human leukocyte antigen (HLA) inherited from the father. We experienced a case of NAIT caused by anti-HLA A29 antibody. The patient was first born female preterm infant. She had no petechiae or purpura and no evidence of infection at birth, but the platelet count was 27,000/mm3. The human platelet antigen specific antibodies were not detected in infant and her mother's sera. On panel reactive antibody (PRA) test, her mother's serum showed 96% HLA A29 antibody. On sequence specific primed polymerase chain reaction (SSP-PCR), anti-HLA A24, A31, B7, B51 antibodies were detected in her mother's serum, and anti-HLA A29, A31, B7, B51 antibodies in infant's serum. And on platelet immunofluorescent flow cytometry test (FCM) her mother's serum showed positive reaction with her father's platelet. These findings suggested that NAIT was caused by anti-HLA A29 antibody. The patient received platelet concentrates and intravenous immunoglobulin. The platelet count increased to 110,000/mm3 on the 32nd day of life and was maintained. On the CGH array performed because of her dysmorphic features, 16p 11.2 (1.2 Mb gain), which was considered benign copy number variation were revealed. We report a case of NAIT caused by anti-HLA A29 antibody accompanied by 16p11.2 (1.2 Mb gain).