title: The management of alloimmune neonatal thrombocytopenia.
abstract: Neonatal alloimmune thrombocytopenia (NAITP), defined as thrombocytopenia (platelet count < 150 x 10(9)/l) due to transplacentally acquired maternal platelet alloantibodies, occurs in approximately 1 per 1200 live births in a Caucasian population. In such a population, the majority (> 75 percent) of cases are due to fetomaternal incompatibility for the platelet specific alloantigen, HPA-1a (P1A1, Zwa). Incompatibility for the HPA-5b (Bra) alloantigen is the next most frequent cause of NAITP in Caucasians; much less common is NAITP due to incompatibility for HLA, blood group ABO or other platelet-specific antigens. In non-Caucasian populations (e.g. Orientals) HPA-1a incompatibility is a rare cause of NAITP and other alloantigens e.g. HPA-4b (Penb, Yuka) are implicated. The greatest clinical challenge relates to the antenatal management of pregnant women alloimmunized to the HPA-1a (P1A1, Zwa) antigen, and particularly the subset of such women who have a history of a previously affected infant with severe thrombocytopenia and/or intracranial hemorrhage (ICH). The risk of antenatal ICH in the fetus of such women is high enough to merit intervention, either weekly infusion of high-dose intravenous immunoglobulin G (IVIG) with or without corticosteroids given to the mother (the preferred approach in North American centres), or repeated in-utero fetal platelet transfusions (the preferred treatment approach in some European centres). Post-natal management of severely affected infants centres on the rapid provision of compatible antigen-negative platelets harvested from the mother or a phenotyped donor. The value of antenatal screening programs to detect 'at risk' alloimmunized women during pregnancy continues to be debated.
authors.affiliation: University of Toronto, Hospital for Sick Children, ON, Canada.
authors.forename: V S
authors.initials: VS
authors.lastname: Blanchette
authors.forename: J
authors.initials: J
authors.lastname: Johnson
authors.forename: M
authors.initials: M
authors.lastname: Rand
mesh_terms: D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D016824:Antigens, Human Platelet / Q000276:immunology; D001792:Blood Platelets / Q000276:immunology; D005260:Female; D006801:Humans; D016756:Immunoglobulins, Intravenous / Q000627:therapeutic use; D007231:Infant, Newborn; D007518:Isoantibodies / Q000276:immunology*; D007519:Isoantigens / Q000276:immunology; D008431:Maternal-Fetal Exchange; D017713:Platelet Transfusion; D011247:Pregnancy; D013921:Thrombocytopenia / Q000175:diagnosis / Q000453:epidemiology / Q000276:immunology* / Q000628:therapy*
chemical_list: D000305:Adrenal Cortex Hormones; D016824:Antigens, Human Platelet; D016756:Immunoglobulins, Intravenous; D007518:Isoantibodies; D007519:Isoantigens