A study from Brazil recently published in Transfusion has identified, for the first time, newborns simultaneously affected by fetal and neonatal alloimmune thrombocytopenia (FNAIT) and neonatal alloimmune neutropenia (NAIN).
The research also points to a surprising culprit: antibodies from the mother’s immune system that target proteins called HLA class I antigens.
The two rare immune blood disorders occur when a mother’s immune system produces antibodies against fetal blood cell antigens inherited from the father. FNAIT targets platelets and can cause bleeding, while NAIN targets neutrophils, leading to infection risk. Although both are uncommon on their own, their concurrent occurrence had not previously been systematically investigated.
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In the new study, researchers tested umbilical cord blood samples from 10,000 newborns. They identified 10 babies with both low platelet and low neutrophil counts at birth. In four of those cases, the mothers’ blood contained antibodies that likely triggered both conditions. One case included a combination of antibodies to platelet, neutrophil and HLA antigens, and three cases showed only anti-HLA class I antibodies. These antibodies were particularly strong in mothers whose babies had the lowest blood cell counts.
Overall, the researchers estimate that about one in every 2,500 babies could be affected by both FNAIT and NAIN at the same time. Their results suggest that testing for HLA antibodies could help identify immune causes of unexplained low blood counts in newborns.
The study adds to growing evidence that certain maternal immune responses can harm the baby’s blood system, even when the usual antibody tests come back negative. Early diagnosis, the authors say, could allow for closer monitoring and quicker treatment to prevent bleeding or infections in affected newborns.
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