NEONATAL ALLOIMMUNE THROMBOCYTOPENIA IN T HE BAK(A) BAK(B) SYSTEM/

Background. - Neonatal alloimmune thrombocytopenia (NAIT) in the HPA-3 a system is responsible for less than 5% of all cases of NAIT. Case re port. - Thomas, a male infant, was born at 39 weeks of gestation after an uncomplicated pregnancy. Delivery was normal. The Apgar score was 9 at 1 minute, and 10 at 5 and 10 minutes. At 1 hour of age, he displa yed extensive petechiae and purpura over the back. The platelet count was 8,000/mm(3). Hematesis and extensive petechiae were noted, leading to an exchange transfusion followed by a transfusion of 0.5 U/kg of r andom donor platelets, 0.4 g/kg/d of intravenous immunoglobulin (IVIg) and 10 mg/kg/d of corticosteroids. IVIg were discontinued on d5 and c orticosteroids on d10. There was no relapse of thrombocytopenia. A neo natal alloimmune thrombocytopenia with an HPA-3a (Bak(a)) incompatibil ity was confirmed. Conclusion. - HPA-3a incompatibility is certainly m ore frequent than the rare cases reported and must be searched for in all cases of neonatal thrombocytopenia.