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.