[Neonatal alloimmune thrombopenia in anti-HPA-3a (Baka) immunization].

Background: Neonatal alloimmune thrombocytopenia (NAIT) in the HPA-3a system is responsible for less than 5% of all cases of NAIT.

Case Report: 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 displayed extensive petechiae and purpura over the back. The platelet count was 8,000/mm3. Hematesis and extensive petechiae were noted, leading to an exchange transfusion followed by a transfusion of 0.5 U/kg of random donor platelets, 0.4 g/kg/d of intravenous immunoglobulin (IVIg) and 10 mg/kg/d of corticosteroids. IVIg were discontinued on d5 and corticosteroids on d10. There was no relapse of thrombocytopenia. A neonatal alloimmune thrombocytopenia with an HPA-3a (Baka) incompatibility was confirmed.

Conclusion: HPA-3a incompatibility is certainly more frequent than the rare cases reported and must be searched for in all cases of neonatal thrombocytopenia.