Fatal hemolytic transfusion reaction due to anti-Ku in a Knull patient

A fatal transfusion reaction due to anti-Ku in a Knull (Ko) patient is reported. The patient was transfused with 34 units of incompatible RBCs during 44 days of hospitalization. Apart from the first transfusion, all subsequent transfusions failed to raise the patient's Hb. No serum antibody was identified until he was transferred to another hospital for dialysis. A compatibility test demonstrated a weak antibody and autocontrol reacting at room temperature by a manual polybrene method. The antibody was considered to be a "cold agglutinin." A blood sample was sent to a reference laboratory where the patient was found to be Knull and the antibody was identified as anti-Ku.