Transient pseudoleukocytosis caused by cryocrystalglobulinemia.

A patient with Sjögren's syndrome and cryoglobulinemia was found to have pseudoleukocytosis when a leukocyte count was performed on an electronic particle counter. This apparent increase in the leukocyte count was found to be caused by spontaneous crystallization of the cryoglobulin. Further studies showed that this phenomenon was transient. Disappearance of the spontaneous crystal formation without a change in the level of cryoglobulin suggests the possibility of an interaction between the cryoglobulin and a plasma component. Factors affecting spontaneous crystallization of cryoglobulins and the laboratory as well as the clinical implications of pseudoleukocytosis are discussed.