Multiple myeloma

Know the renal complications of multiple myeloma

• Bence Jones proteinuria and cast nephropathy

• Amyloidosis

• Light-chain nephropathy

• Hypercalcemia and hyperuricemia

• Vascular disease

• Urinary tract obstruction w/ secondary pyelonephritis

• Most commonly, these complications lead to chronic renal failure that progresses slowly over months  years

• Precipitating factors can lead to acute renal failure (see below)

How does Bence Jones proteinuria cause renal insufficiency?

• Some light chains are directly toxic to epithelial cells

• BJ proteins combine w/ urinary glycoprotein (Tamm-Horsfall protein) under acidic conditions to for m large, distinct tubular casts. These casts not only obstruct the tubular lumina, but also evoke a peritubular inflammatory reaction (cast nephropathy)

Know the characteristics of tubular cast in multiple myeloma

• Casts appear as pink  blue amorphous masses, sometimes concentrically laminated.

• Casts are surrounded by multinucleate giant cells

• Surrounding epithelium is often necrotic

• Adjacent interstitial tissue shows nonspecific inflammatory reaction

Know the precipitating factors of ARF in multiple myeloma

• Dehydration

• Hypercalcemia

• Acute infection

• Nephrotoxic antibiotics

Category: Pathology Notes