Crystal-storing histiocytosis: A disorder occurring in plasmacytic tumors expressing immunoglobulin kappa light chain

Intracellular immunoglobulin crystal formation within plasma cells is an un common finding in multiple myeloma and other lymphoplasmacytic tumors. We p resent 12 cases of plasmacytic tumors with prominent crystal formation, inc luding myeloma (5 cases), lymphoplasmacytic lymphoma (6 cases), and a nonne oplastic plasma cell. proliferation. In all cases, crystal formation was as sociated with the proliferation of variable numbers of histiocytes containi ng similar inclusions. These cases showed a variety of appearances, sometim es obscuring the underlying plasma cell tumor and raising the differential diagnosis of a storage disorder, hemophagocytosis, or a mesenchymal lesion. In cases of lymphoplasmacytic lymphoma, patients typically presented with marked paraproteinemia and symptoms of hyperviscosity. Crystal-storing hist iocytosis was not associated with other immunoglobulin deposition disorders , including amyloidosis, Mott cell tumors, or kappa-light chain deposition. In our cases and those previously reported, we found an over overwhelming association of crystal-storing histiocytosis (CSH) with tumors expressing i mmunoglobulin kappa light chain with no consistent association with a parti cular heavy chain. These results suggest that CSH results from the ingestio n of crystals produced by plasma cell tumors that either overproduce kappa light chain or express a structurally aberrant molecule. CSH persists in th e marrow and other sites throughout the course of the disease and in our se ries was not highly associated with development of the adult Fanconi syndro me or rapid clinical deterioration. Copyright (C) 1999 by W.B. Saunders Com pany.