AL amyloidosis complicating
monoclonal gammopathy of undetermined significance (MGUS) has usually a predominant glomerular deposition of lambda light chain. Heavy
proteinuria is one of its cardinal manifestations. A 78-year-old man with a 9-year history of
IgG kappa light-chain-MGUS and normal urine
protein excretion developed severe
renal failure. Serum levels of kappa light chain and serum
IgG had been stable while
proteinuria was absent throughout the nine-year period. For the first eight years, he had stable stage III
chronic kidney disease attributed to
bladder outlet obstruction secondary to prostatic
malignancy. In the last year, he developed progressive serum
creatinine elevation, without any increase in the serum or urine levels of
paraproteins or any sign of
malignancy. Renal ultrasound and
furosemide renogram showed no evidence of urinary obstruction. Renal biopsy revealed
AL amyloidosis, with reactivity exclusive for kappa light chains, affecting predominantly the vessels and the interstitium. Glomerular involvement was minimal.
Melphalan and
prednisone were initiated. However, renal function continues deteriorating. Deposition of AL kappa
amyloidosis developing during the course of MGUS predominantly in the wall of the renal vessels and the renal interstitium, while the involvement of the glomeruli is minimal, leads to progressive
renal failure and absence of
proteinuria. Renal biopsy is required to detect both the presence and the sites of deposition of renal AL kappa light chain
amyloidosis.