Neonatal alloimmune thrombocytopenia involving HPA-5b (Br(a)): a rare Japanese case.

Neonatal alloimmune thrombocytopenia (NAIT) is caused by platelet antigen incompatibility between the mother and fetus. The frequency of NAIT varies among ethnic groups. In Caucasians, HPA-5b (Br(a)) is the antigen that is second most frequently implicated. In Japan, NAIT due to anti-HPA-5b antibody is quite rare. The present case is the second case of Br(a)-NAIT in Japanese and the first case serologically confirmed by monoclonal antibody-specific immobilization of platelet antigens.