OBJECTIVES: We describe a 62-year-old woman with a 15-year history of a plasma cell dyscrasia (monoclonal IgGkappa), manifested by type I cryoglobulinemia and dermal vasculitis.METHODS: In addition to the clinical examinations, light microscopy with immunohistochemistry, sequential multicolor immunohistochemistry, and electron microscopy were used to characterize the crystalline deposits.RESULTS: At initial presentation and for a later flare, she was treated with cyclophosphamide and prednisolone with good clinical response. She had renal function decline, microscopic hematuria, and proteinuria. A renal biopsy specimen revealed the presence of glomerular macrophages and duplication of the capillary walls with cellular interposition. Glomerular cells contained abundant needle-shaped eosinophilic crystalline inclusions positive for kappa light chain. Electron microscopy confirmed the presence of intracytoplasmatic crystalline structures in endothelial cells, podocytes, and macrophages but not in the tubular epithelium. Rituximab treatment was started. At follow-up (now up to 6 months), renal function remained stable.CONCLUSIONS: This patient displays a unique renal manifestation of type I cryoglobulinemia related to a plasma cell dyscrasia.