Autoanti-K antibody mimicking an alloantibody.

A patient with pancytopenia and hypercellular bone marrow but without evidence of hemolysis had a positive direct antiglobulin test due to a red blood cell autoantibody. Although the patient was K-negative, eluates made from his erythrocytes contained what seemed to be anti-K antibody. The latter could be adsorbed onto and eluted from both K-positive and K-negative cells. We concluded that this patient is another example of autoanti-K antibody mimicking an alloanti-K antibody.