An Atypical Case of Neonatal Alloimmune Thrombocytopenia.

Fetal and neonatal alloimmune thrombocytopenia (FNAIT) results from maternal antibodies targeting fetal platelets during pregnancy, often causing hemorrhagic manifestations detectable antenatally or shortly after birth. We report an atypical form of FNAIT with delayed onset in a healthy, breastfed male infant who developed diffuse petechiae 2 weeks after birth due to severe thrombocytopenia. The mother was shown to be negative for the human platelet antigen-1a (HPA-1a) allele but had anti-HPA-1a IgG antibodies, while the father and newborn were HPA-1a positive, confirming the diagnosis. Despite intravenous immunoglobulins and platelet transfusions, the recovery was slow. Analysis of breast milk demonstrated the presence of anti-HPA-1a IgG antibodies. The unusual clinical presentation 2 weeks after birth and the slow platelet recovery under appropriate treatment suggest postnatal transfer of maternal anti-HPA-1a antibodies or B lymphocytes producing these antibodies to the newborn, which may possibly have occurred through breastfeeding. Further research is needed to validate these findings and understand the role of breast milk in provoking the disease. Early detection and management remain essential to prevent serious complications associated with FNAIT.