Neonatal alloimmune thrombocytopenia due to Anti-HPA-1b (PL(A2)) (Zw^b)

Background: Neonatal alloimmune thrombocytopenia is a rare condition due to passively acquired maternal antibodies directed against paternal platelet antigens inherited by the infant. Only 5 cases have been reported due to antibodies against HPA-1b (PL(A2)) (Zw^b). Case Report: We report a case of neonatal alloimmune thrombocytopenia due to anti-HPA-1b in the second pregnancy of a 26-year-old Caucasian female. The male infant was treated with a 5-day course of intravenous immunoglobulin without complications. We report the HLA phenotype of the infant's mother and summarize the previous case reports due to anti-HPA-1b. Conclusion: Based on this case and a review of the literature, intravenous immunoglobulin as well as random donor exchange transfusion and random donor platelet transfusions are effective in the treatment of neonatal alloimmune thrombocytopenia due to anti-HPA-1b. Obvious associations between HLA alleles and sensitization to HPA-1b have not been elucidated.