Renal failure is a major cause of morbidity and mortality in patients with multiple myeloma. Of those patients with newly diagnosed multiple myeloma, up to 50% have renal impairment and 12–20% have acute kidney injury, and among those patients with acute kidney injury, 10% become dependent on dialysis. They represent 2% of the dialysis population (0.1% in Japan [1]) and there are approximately 5000 new patients, worldwide, each year. The most common renal lesion is cast nephropathy in the distal tubules, which leads to interstitial fibrosis. In these patients, a large amount of serum-free light chains readily pass through the glomeruli and overwhelm the absorptive capacity of the proximal tubules [2].