Waldenström's macroglobulinemia associated with a mixed cryoglobulin. Report of a case with partial precipitation in vitro at 37 degrees C.

A 68-year-old man had Waldenström's macroglobulinemia associated with a mixed cryoglobulin (monoclonal IgM kappa and polyclonal IgG, 0.96 g/dL) manifested by purpura, weight loss, hepatosplenomegaly, and proteinuria. On cooling of serum warmed to 50 degrees C, the cryoglobulin begins to precipitate above 40 degrees C, with substantial precipitation at body temperature. Incubation at 37 degrees C (after equilibration at 50 degrees C) causes approximately two thirds of the cryoglobulin to precipitate in 30 to 60 minutes; the precipitate dissolves on rewarming the serum to 50 degrees C. The ability of this cryoglobulin to precipitate at 37 degrees C in vitro indicates that the temperature spectrum of cyroglobulin precipitation can extend to body temperature or above it, and suggests that some serum samples that contain cryoglubulins must be separated quickly at a temperature of 37 degrees C or higher.