Cytoplasmic inclusions in leukocytes - An unusual manifestation of cryoglobulinemia

Cryoglobulins are circulating immunoglobulins characterized by reversible, cold-induced precipitation. A variety of laboratory abnormalities, includin g hypocomplementemia, elevated erythrocyte sedimentation rate, rheumatoid f actor activity, pseudoleukocytosis, and pseudothrombocytosis, are associate d with cryoglobulinemia. Extracellular; faintly basophilic, amorphous depos its of cryoglobulins occasionally have been described in blood smears. In t he present study, smears prepared from blood collected at room temperature from 6 patients with cryoglobulinemia exhibited neutrophil and, occasionall y monocyte inclusions containing clear light pink, or faintly basophilic am orphous material. The inclusions were absent in smears from blood collected and maintained at 37 degrees C. Ultrastructural examination revealed that the material within the leukocyte inclusions was consistent with phagocytos ed immunoglobulins. The identification of characteristic cytoplasmic inclus ions in leukocytes may be an important clue in the early recognition of cry oglobulinemia.