A 46-year-old female patient who developed acute myelogenous leukemia in October, 1995, required red blood cell transfusion from day 9 and continuous platelet transfusion from day 13 after the beginning of antileukemic chemotherapy. When total transfused platelets reached 130 units, platelet transfusion refractoriness (PTR) occurred. A high anti-HPA-5a antibody titer (×4, 096) was detected using the MPHA method when 300 units were transfused. The antibody titer declined thereafter, but the antibody and PTR lasted throughout the clinical course, whereas anti-HLA antibody was not detected. There were no physical signs that caused the persistent PTR. HPA-matched platelet transfusion was tried once around the terminal stage of the disease, but efficacy was not confirmed because of the presence of severe infection and bleeding tendency. These findings therefore suggest this to be a unique case in that anti-HPA-5a antibody alone caused platelet transfusion refractoriness.
