Transfusion-related alloimmune neutropenia: an undescribed complication of blood transfusion.

Alloimmune neutropenia in neonates is rare. We describe severe and persistent neutropenia in a 4-week-old neonate, which arose within 2 h of a transfusion of blood that contained about 28 mL of plasma and in which strong antibodies against human neutrophil antigen 1b (HNA-1b) were subsequently identified. The infant was positive for HNA-1b. No other likely cause of neutropenia was discovered. We believe this complication of blood transfusion to be a previously unrecognised one, and have called the condition transfusion-related alloimmune neutropenia (TRAIN).