Crystal-storing histiocytosis involving the kidney in a low-grade B-cell lymphoproliferative disorder

uncommon presentation. In all cases, crystal formation is associated with accumulation of histiocytes containing light chain or immunoglobulin inclusions, and the disorder has been termed crystal-storing histiocytosis. We report a case of crystal-storing histiocytosis affecting the kidney with prominent infiltration of the mesangium by large mononuclear and multinuclear cells that contained eosinophilic crystalline material in the setting of a low-grade B-cell lymphoproliferative disorder. The interstitium did not contain similar crystal-containing histiocytes. On electron microscopy, the mononuclear and multinuclear cells in the mesangium were filled with rhomboid and needle-shaped crystals. Immunofluorescence studies showed the material to be positive for X light chains but negative for K light chains. To our knowledge, this is the first report of crystal-storing histiocytosis involving the kidney in a low-grade B-cell lymphoproliferative disorder with an immunophenotype of a marginal zone lymphoma and of exclusive expansion of the mesangium by infiltrating histiocytes containing needle-shaped and rhomboid crystals that were positive for A light chains. We report this case to illustrate an unusual finding of mesangial infiltration by crystal-storing histiocytes, and we review the literature of renal involvement by crystal-storing histiocytosis and crystal deposition in lymphoproliferative disorders. (C) 2002 by the National Kidney Foundation, Inc.