Normalization of platelet count is not related to the amount of transfused platelets in neonatal alloimmune thrombocytopenia – Report of a case series with three neonates

Neonatal Alloimmune Thrombocytopenia (NAIT) is an antibody-mediated disease characterized by low platelet (PLT) counts. Caused by diaplacental transfer of maternal alloantibodies predominantly directed against human PLT antigen-1a HPA-1a and HPA-5b. Even PLT transfusion is a major treatment approach in management of NAIT, there is no consensus regarding the PLT count threshold as well as the amount of PLT concentrates that are needed to achieve PLT counts that prevent from bleeding. We analyzed appearance, development and transfusion efficacy.

Hospital data base was screened for neonates presented with thrombocytopenia and suspicion of NAIT (2019 to 2023). Laboratory data including PLT count and HPA genotyping. Neonates were examined by head ultrasound and were also tested for congenital infections to exclude infectious cause of thrombocytopenia. Two mothers had HPA-1a antibody one had HPA-15b antibody, none of them showed HLA antibodies.

Overall 89 were included. 19/89 neonates presented with thrombocytopenia suspected to be related to NAIT. Day three post-partum 3/19 patients that were delivered vaginally week 38/40 of gestation without any complications developed petechiae at back and legs as well as marked thrombocytopenia. Although, subsequent performed ultrasound diagnostics did not reveal additional bleeding signs. The clinical suspicion of NAIT was raised in all three individuals. To prevent aggravation of bleeding symptoms,transfusion was initiated. Following transfusion of one PLT concentrate in two patients and 13 PCs in one individual. PCs were HPA-1a and HPA-5b-negative. No intracranial hemorrhage was observed.

NAIT is a rare event, there is no consensus regarding indication and amount of PCs that are required to achieve a sufficient PLT count that prevents bleeding complications. Following transfusion of HPA-matched PCs, no serious adverse effects were reported. Therefore, indicate a immediate transfusion. A future trial is required to define the amount of needed PC and requirement of prophylactic transfusion. Immune-mediated process of NAIT as well as of platelet transfusion itself has to be elucidated. Question arises as to whether it makes sense to carry out a screening or to establish a register. Moving forward, continued research and clinical vigilance are essential to improving the burden of this potentially devasting condition.

The authors declare, that there are no conflicts of interest in relation to this work.