A new high‐prevalence LW antigen detected by an antibody in an Indigenous Australian homozygous for LW*A c.309C>A variant

Background and Objectives The LW gene encodes the LW glycoprotein that carries the antigens of the LW blood group system. LW antigens are distinct from D antigen, however, they are phenotypically related and anti‐LW antibodies are often mistaken as anti‐D. An antibody was detected in an Australian patient of Aboriginal descent who consistently typed as LW(a+b−). This study aimed to describe the antibody recognizing a high‐prevalence antigen on the LW glycoprotein. Study Design and Methods Samples from the patient and her four siblings were investigated. DNA was genotyped by single nucleotide polymorphism (SNP)‐microarray and massively parallel sequencing (MPS) platforms. Red blood cells (RBCs) were phenotyped using standard haemagglutination techniques. Antibody investigations were performed using a panel of phenotyped RBCs from adults and cord blood cells. Results SNP‐microarray and MPS genotyped all family members as LW*A / A , (c.299A), predicting LW(a+b−). In addition, a novel LW*A c.309C>A single nucleotide variant was detected in all family members. The patient and one of her siblings (M4) were LW c.309C>A homozygous. Antibody from the patient reacted positive to all reagent panel RBCs and cord blood cells but negative with RBCs from LW(a−b−), Rh null and sibling M4. Antibody failed to react with RBCs treated with dithiothreitol. Conclusion Antibody detected in the patient recognized a novel high‐prevalence antigen, LWEM, in the LW blood group system. LWEM‐negative patients who developed anti‐LWEM can be safely transfused with D+ RBCs, however, D− is preferred. Accurate antibody identification can help better manage allocation of blood products especially when D− RBCs are in short supply.