Neonatal Thrombocytopenia Due to Dual Alloimmune and Autoimmune Mechanisms.

Alloantibody-mediated and autoantibody-mediated immune destruction are common causes of early neonatal thrombocytopenia. The authors report a case of severe, early-onset thrombocytopenia with mucocutaneous bleeding in an otherwise well-appearing full-term neonate. Recurrence of thrombocytopenia following initial treatment and its persistence after 2 weeks of life suggested a dual immune mechanism. This is a rare case of immune thrombocytopenia caused by human platelet antigen-5b alloimmunization and passive transfer of maternal antiplatelet antibodies. Appropriate, timely treatment and absence of severe bleeding complications, namely intracranial hemorrhage, conferred a good overall prognosis.