CASE-REPORT - IMMUNOGLOBULIN M-MEDIATED, TEMPERATURE-DEPENDENT NEUTROPHIL AGGLUTINATION AS A CAUSE OF PSEUDONEUTROPENIA

The authors report the case of a 77-year-old man in whom intermittent neutropenia developed during a prolonged hospitalization. Laboratory r ecords revealed wide variations in the patient's routine leukocyte cou nts, Examination of the peripheral smear revealed clumps of 2-3 polymo rphonuclear leukocytes throughout the slide and large aggregates (>50 cells) along the smear edges. Neutrophil clumping also was observed in blood anticoagulated with citrate or heparin. Replacement of patient plasma with saline prevented agglutination. Addition of patient plasma or serum to normal cells induced neutrophil agglutination. Holding th e patients blood at 37 degrees C prevented agglutination, which occurr ed spontaneously and more exuberantly as the temperature was reduced t o 22 degrees C. Flow cytometry revealed immunoglobulin M on neutrophil surfaces. Spontaneous agglutination resolved 6 months after resection of the patient's subsequently diagnosed colon cancer. This is the fir st report of immunoglobulin M-induced neutrophil clumping occurring in the setting of malignancy, and the first reported immunoglobulin M no t to require ethylenediaminetetraacetic acid as a cofactor for aggluti nation.