Abstract
We encountered a case of platelet transfusion refractoriness (PTR) due to low-titer anti-human leukocyte antigen (HLA) antibodies. The patient was a teenage girl with aplastic anemia admitted to our hospital in June 2011. Initially, good responses were obtained with random apheresis platelets (PLT), but from day 16 (the fifth platelet transfusion), we often observed low 1-hour post-transfusion corrected platelet count increments (CCI-1). We suspected immunologic PTR. We detected low-titer HLA antibodies (specificity: anti-HLA-A31, B51) by bead array technology in patient serum obtained on day 22, although we did not detect any anti-HLA or anti-human platelet antigen (HPA) antibodies by the mixed-passive hemagglutination test (MPHA) or anti-human globulin lymphocyte cytotoxicity test (AHG-LCT). Generally good increments were subsequently obtained by directed-donor and HLA-matched PLTs (HLA-PLT). HLA antibodies developed in spite of no presensitization, in a relatively short period after starting PLT transfusion therapy. Moreover, the antibodies caused PTR even at a low titer.
