Crystalline deposits in ascites in a case of cryoglobulinemia.

Crystalline inclusions were observed on routine cytologic studies of ascitic fluid from a patient with exudative ascites of undetermined cause. These inclusions were polymorphic, but frequently appeared as slender needles. They were seen most often in histiocytes and, less frequently, in mesothelial cells and plasma cells. Extracellular crystals were also seen. The crystals were also present in biopsy specimens of peritoneum, liver and bone marrow. Special studies by polarizing light microscopy, cytochemistry, electron microscopy and immunocytochemistry suggested that the crystals were most probably immunoglobulins synthesized by plasma cells. Some were excreted extracellularly and phagocytized by histiocytes. Further studies indicated that the patient had an indolent plasma-cell dyscrasia, resulting in excessive production of a monoclonal immunoglobulin. The immunoglobulin may have crystallized and become deposited in tissues, inciting chronic inflammatory changes. Massive deposits of crystals in the peritoneum, with the resultant inflammatory reaction, was possibly the cause of the formation of ascites.