RESUMEN
As a minor blood antigen, the Duffy blood group has 5 antigens which are Fya, Fyb, Fy3, Fy4 and Fy5. When the Duffy group is implicated in delayed transfusion reactions, one expects to find anti-Fya rather than Fyb. We experienced a case of delayed hemolytic transfusion reaction caused by anti-Fyb antibody. A 69 year-old woman was referred having had hematuria, fever, chill and jaundice 9 days after transfusion. The hemoglobin was 9.5mg/dl, reticulocyte count 1.4%, liver function test showed total bilirubin 10.8mg/dL, LDH 5,225IU/L, alkaline phosphatase 26IU/L. Indirect antiglobulin test was positive, while the direct one was negative. A delayed hemolytic transfusion reaction was suspected as patient's serum was reacted with panel cells for the antibody identification test and the anti-Fyb was finally identified. The patient recovered without specific treatment. There were no severe complication and sequele.It appears to be the first reported case of hemolytic transfusion reaction caused by anti-Fyb in Korea.