Neonatal alloimmune neutropenia associated with maternal anti-HLA antibodies: a conservative interpretation of a rare presentation

Neonatal alloimmune neutropenia (ANN) is a rare cause of neutropenia in newborns, resulting from maternal antibodies directed against paternal antigens present on fetal neutrophils, in a mechanism similar to Rh haemolytic disease.We present the case of a full-term newborn with severe neutropenia from birth (nadir 110/µL) but no clinical signs of infection. As neutropenia persisted beyond the neonatal period, an immunological study was performed, identifying maternal IgG anti-human leukocyte antigen (HLA) class I and II antibodies and positive cross-match tests against paternal and neonatal neutrophils. While these findings suggest anti-HLA antibodies likely contributed to the neutropenia, the absence of glycoprotein-specific confirmatory assays—such as MAIGA (monoclonal antibody immobilisation of granulocyte antigens) or immunoprecipitation—prevents definitive causal attribution.The outcome was favorable with no need for treatment. Neutropenia resolved spontaneously at 22 weeks of life.Current literature on this entity is reviewed, highlighting its transient nature and good prognosis in most cases.