Renal damage in multiple myeloma develops gradually over several years. Excretion of free light chains in urine (Bence-Jones proteins) occurs in about 70% of multiple myelomas. The free light chains precipitate and get deposited as casts in distal and collecting tubules - a condition referred to by a variety of names, including myeloma kidney, light chain cast nephropathy or Bence-Jones cast nephropathy. The resulting tubulo-interstitial inflammation causes progressive decline in renal function. The patients develop proteinuria in the non-Nephrotic range (usually < 3 gm protein loss in urine/day) consisting predominantly of immunoglobulin light chains (Bence-Jones proteins). Occasionally, the chronic renal insufficiency is complicated by acute renal failure that may be precipitated by dehydration, hypercalcemia, hyperuricemia, infections, intravenous contrast media, or treatment with nephrotoxic drugs. The image shows myeloma kidney in the center and on the left. A normal kidney is shown on the right for comparison. The myeloma kidney appears pale and scarred due to a combination of deposition of casts in the tubules, inflammation and fibrosis. Image copyright: pathorama.ch.