Summary

Neonatal alloimmune thrombocytopenia is a rare (1/1000–5000 births) life-threatening disorder, caused by fetomaternal incompatibility for a fetal human platelet alloantigen inherited from the father, with production of maternal alloantibodies against fetal platelets, leading to severe thrombocytopenia and potential bleeding. Intracranial haemorrhage is the most feared complication. This report presents the case of a term newborn infant, born from caesarean section after a normal pregnancy, presenting signs of skin bleeding with different ages. Obstetric history included a previous spontaneous abortion after amniocentesis. Severe thrombocytopenia (4×10⁹/l platelets) was found and brain ultrasound showed multiple intracranial haemorrhages. Human platelet antigen (HPA) phenotyping showed maternal negative HPA-1a and paternal positive HPA-1a platelets. Strongly positive anti-HPA-1a and weakly positive anti-human leukocyte antigen class I alloantibodies were found in the mother. Multiple platelet transfusions, intravenous immunoglobulin and corticosteroid were given but favourable response was accomplished only after a compatible platelet transfusion. Brain MRI showed multiple subacute and chronic haemorrhages.