Neonatal Alloimmune Thrombocytopenia

Neonatal alloimmune thrombocytopenia (NAITP or NAIT or NAT for short; or fetal and neonatal alloimmune thrombocytopenia, FNAIT, feto-maternal alloimmune thrombocytopenia, FMAITP or FMAIT) is a disease that affects fetuses and newborns, in which the platelet count is decreased (a state known as thrombocytopenia). Platelet antigens are inherited from both mother and father. FNAIT is caused by antibodies specific for platelet antigens inherited from the father but which are absent in the mother. Fetomaternal transfusions (or fetomaternal hemorrhage) results in the recognition of these antigens by the mother's immune system as non-self, with the subsequent generation of allo-reactive antibodies which cross the placenta. NAIT, hence, is caused by transplacental passage of maternal platelet-specific alloantibody and rarely human leukocyte antigen (HLA) allo-antibodies (which are expressed by platelets) to fetuses whose platelets express the corresponding antigens. NAIT occurs in somewhere between 1/800 and 1/5000 live births. More recent studies of NAIT seem to indicate that it occurs in around 1/600 live births in the Caucasian population.