Case report: atypical presentation of anti-Rg(a)

The Rodgers (Rg(a)) antigen is a plasma protein that binds to the red blood cell (RBC) membrane. About 2 to 3% of the transfusion-recipient white population lacks the antigen and can produce anti-Rg(a) antibody. We report the case of a 70-yr-old man who presented with a medical history of hairy cell leukemia and profound pancytopenia that required RBC and platelet (PLT) transfusions. The patient had received 2 units of RBCs and 4 PLT concentrate pools. He was typed as O Rh(D) positive, with positive reactions in all 3-screen cells using the polyethylene glycol (PEG) indirect antiglobulin test/IAT (anti-IgG). Three antibody identification panels were performed, which all proved to be negative. A direct antiglobulin test and an auto-control were run, which were also negative. Since further investigations were needed, the patient's blood sample was sent to a reference laboratory where anti-Rg(a) was identified. Since the percentage of antigen-positive cells in the red cell panel was low, crossmatch compatible units of RBCs were transfused with no discernible immediate or delayed transfusion reaction. This report should alert hospital transfusion service personnel to recognize that, although the panel cells are usually reliable for antibody identification purposes, they may not have the antigens that are present on the screening cells.