Clinical, biochemical, and pathological features in a patient with plasma cell dyscrasia and Fanconi syndrome.

Multiple myeloma is associated with a wide array of renal diseases that include myeloma cast nephropathy, monoclonal immunoglobulin deposition disease, amyloidosis, cryoglobulinemia, tubular dysfunction, pyelonephritis, nephrocalcinosis, urate nephropathy, and infiltration by atypical plasma cells (or myeloma cells). Filtered immunoglobulin light chains may affect both the distal and, more frequently, the proximal tubule. Tubular abnormalities in patients with plasma cell dyscrasia may be more frequent than previously thought. A patient with a plasma cell dyscrasia is described, who presented with biochemical features consistent with Fanconi syndrome. Immunoelectron microscopy performed on the renal biopsy confirmed the presence of kappa light chain immunoglobulin in intracytoplasmic crystals in proximal tubular epithelial cells. This report is one of a few demonstrating the presence of light-chain immunoglobulin in intratubular crystals in a human renal biopsy obtained from a patient with a plasma cell dyscrasia and Fanconi syndrome.