Cold agglutinin disease by autoanti-i blood type antibody associated with B cell chronic lymphocytic leukemia

Cold agglutinin (CA) disease is a rare complication of B cell chronic lymphocytic leukemia (CLL). We report a case of CA disease by autoanti-i blood type antibody associated with CD5-negative CLL. The specificity of cold agglutinin in the sera and eluates from red blood cells were analyzed by reactivity against panels of red blood cells and also hemagglutinin inhibition assay using lactonorhexaosylceramide, and were determined to be an anti-i blood group antibody of the monoclonal IgM kappa isotype. PCR analysis of immunoglobulin heavy-chain genes from bone marrow-derived genomic DNA showed CLL cells utilizing DP-54 as a VH gene, differing from the reported VH genes used for cold agglutinin with anti-I/i specificity. The anti-i antibody in this patient might be secondarily produced by residual B cells due to an immunodysregulatory state, and not from CLL cells.