Delayed haemolytic transfusion reaction due to anti‐M antibody

A female patient with delayed haemolytic transfusion reaction due to anti‐M antibody is described. Diagnosis was based on laboratory evidence of haemolysis and on characteristic serological findings. Anti‐M was detected in the recipient's serum 7 d after the last transfusion episode. This alloantibody had not been present in the pretransfusion serum. In addition, the direct antiglobulin test was positive on post‐transfusion testing and the implicated antibody was eluted from post‐transfused red cells.