Fetoneonatal alloimmune thrombocytopenia (FNAIT): our experience

Fetoneonatal alloimmune thrombocytopenia (FNAIT) is a relatively rare clinical syndrome characterized by marked thrombocytopenia shortly after birth. It occurs when fetal platelets are destroyed, after sensitization, by a transplacental passage of maternal antibodies directed against a fetal platelet alloantigen inherited from the father. This article reviews some pathophysiologic and clinical aspects of FNAIT.

We also present our experience with the management of 12 newborns affected with a symptomatic form of this disorder in order to verify what would be the best diagnostic and therapeutic protocols.

Antibody identification in maternal serum showed 9 anti-HPA-1a (75% of cases), 2 anti-HPA-1b (17%) and 1 anti-HPA-1a+anti-Gp IV+anti-HLA class I (8%).

Sixteen human platelet alloantigen (HPA) systems have been identified, six major (from HPA 1 to 5 and HPA 15) and ten rare or private, each composed of two allelic antigens (named "a" or "b", according to major or minor frequency in the population). All HPA systems, including private or low frequency, may play a role in determining FNAIT. Unfortunately FNAIT cannot be prevented, in fact no one of maternal parameters is predictive of thrombocytopenia or its magnitude.