Anti-LW masquerading as anti-D in a D+ patient.

LW^a, LW^ab, LW^b, and LWEM are the four main antigens of the Landsteiner-Weiner (LW) blood group system. LW expression may be weakened during pregnancy and immune dysregulation, with the subsequent appearance of anti-LW. Here, we describe a case of an elderly male patient in whom transfusion of red blood cells (RBCs) became challenging because of the presence of anti-LW. A 61-year-old male patient presented with shortness of breath and a hemoglobin level of 7.0 g/dL, requiring RBC transfusions. Serologic workup of his blood sample showed his RBCs to be group A, D+, but his serum was incompatible with several group A, D+ donor RBC units. Antibody screening showed preferential reactivity with D+ panel RBCs that was abolished when using 0.2 M dithiothreitol-treated RBCs. The patient's serum did not react with known RBCs of Rh_null and LW(a-) phenotypes but reacted strongly with D+ and D- cord RBCs. The patient's sample was genotyped as LW*A/A (c.299A), consistent with the LW(a+b-) phenotype. Subsequent bone marrow examination showed B-lymphoproliferative disorder. The patient required RBC transfusion support because of his underlying disease. Transfusion of group A, D- RBCs was uneventful. The expression of LW in this patient was possibly weakened by his underlying disease, leading to the development of anti-LW. No complications were seen after multiple transfusions of group A, D- RBC units.