Multi‐organ involvement with crystal‐storing histiocytosis

Abstract

A 65-year-old man underwent a renal transplant for what was thought to be interstitial nephritis. His graft did not function as well as expected and he underwent renal biopsies to investigate this. These demonstrated an extensive infiltrate by crystal-containing macrophages throughout the grafted kidney. The crystal shapes varied but there were many rhomboid and spindle forms, seen most clearly on electron microscopy (top). A bone marrow trephine biopsy performed at this time demonstrated an extensive infiltrate of histiocytes packed with immunoglobulin crystals (bottom). A review of his diagnostic renal biopsy from 2 years previously confirmed the presence of these crystals. This rare phenomenon, crystal-storing histiocytosis, can be associated with myeloma but examination of urine, serum and bone marrow did not detect any monoclonality at that time. However a serum free-light chain assay subsequently performed did show a kappa excess, confirming plasma cell clonality.