Abstract
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.
Highlights
The term monoclonal gammopathy of undetermined significance (MGUS) covers a spectrum of conditions characterized by production of a monoclonal immunoglobulin
We present a patient who developed renal AL kappa amyloidosis manifested by progressive renal failure without proteinuria after several years of MGUS with stable paraprotein levels and renal function
A great variety of renal histological lesions has been associated with MGUS
Summary
The term monoclonal gammopathy of undetermined significance (MGUS) covers a spectrum of conditions characterized by production of a monoclonal immunoglobulin. A variety of life-threatening conditions may complicate MGUS. The list of conditions complicating MGUS includes multiple myeloma, Waldenstrom’s macroglobulinemia, other lymphoproliferative malignancies such as chronic lymphocytic leukemia and IgM lymphoma, other hematologic malignancies, AL amyloidosis, chronic inflammatory demyelinating polyradiculopathy, autonomic neuropathy, osteoporosis, fractures of vertebrae and hips, liver and kidney transplants, hypercalcemia, and urticaria [3,4,5]. With a variety of histological pictures, complicates frequently the course of MGUS [6]. AL amyloidosis with renal deposits of light chains is one of the conditions which may complicate. We present a patient who developed renal AL kappa amyloidosis manifested by progressive renal failure without proteinuria after several years of MGUS with stable paraprotein levels and renal function. Absence of extensive amyloid deposits in the glomeruli was the apparent reason for the absence of proteinuria in this patient
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