[Two serial events of delayed hemolytic transfusion reactions due to different primary immune response-induced irregular antibodies].

A 74-year-old woman with a history of pregnancies, but without previous transfusions, received a red blood cell transfusion for aplstic anemia. She lost consciousness due to severe anemia two weeks later and was transported by ambulance to our hospital. Delayed hemolytic transfusion reaction (DHTR) was diagnosed based on the detection of anti-E antibody and positive E antigen of the previously transfused product. A transfusion of E antigen-negative red cell products was performed. However, DHTR due to anti-c antibody developed 16 d after the transfusion of a c antigen-positive product. Based on the onset of ≥14 d after the transfusions and the detection of a causative IgM-type antibody, DHTR due to a primary immune response was diagnosed. Because the incidence of DHTR is low, physicians rarely experience it in clinical practice. However, in our case, DHTR due to a primary immune response, which is even rarer in DHTR cases, developed twice within a short period. A history of transfusion and pregnancy as well as preexisting irregular antibodies have been identified as risk factors for DHTR. Thus, more attention should be paid to the risk of DHTR redevelopment by repeated transfusions.