[Report of two cases of neonatal alloimmune thrombocytopenia caused by anti-HLA antibody, and their screening using umbilical cord blood].

Here reported are two cases with neonatal alloimmune thrombocytopenia (NAITP). In our 2 cases, anti-HLA antibodies, i.e. anti-HLA-A24+B51 and anti-HLA-Bw61+Cw3, respectively, were detected in the mother's sera, which reacted to each patient's lymphocytes and were presumed to have been contribute to NAITP. The thrombocytopenia, found on routine laboratory examination, recovered within 1 to 3 weeks without any therapy in both cases. Further, the relationship of platelet count and PAIgG in neonatal babies (umbilical cord blood) to anti-HLA antibodies in their mothers were examined in 284 pairs. Thrombocytopenia less than 150,000/microliters was found in 16/284 babies (5.6%), 3 of the 16 (1.1% of the total) being positive for anti-HLA, and one positive for PAIgG. Four (1.4%) of the 284 babies were positive for PAIgG, one of whom was thrombocytopenic, and one positive for anti-HLA. Anti-HLA antibody was found in 25/284 mothers (8.8%). Nevertheless, none of the pairs showed positive reactions in all of three tests. It seems that passive transfer of maternal anti-HLA antibodies to the fetus is not itself sufficient to cause thrombocytopenia. On the other hand, some NAITP cases may have been overlooked because of their mildness.