Myeloma-Associated Fanconi Syndrome Due to λ-Light Chain Crystal Deposition

Multiple myeloma is uncommonly complicated with Fanconi syndrome, due to the deposition of light chains in renal tubular epithelial cells. A 76-year-old man with λ-Bence Jones type multiple myeloma had adult Fanconi syndrome. Electron microscopy showed that rhomboid, high-density substances of various sizes, were accumulated in the proximal tubular epithelial cells on renal biopsy. Immunoelectron microscopy demon-strated that these crystals were λ-light chains. The deposition of κ-light chain in patients with myeloma-associated Fanconi syndrome has been known. This is the 1st report showing the deposition of λ-light chain in renal proximal tubular epithelial cells.