A Patient with Abnormal Kidney Function and a Monoclonal Light Chain in the Urine

Abstract

Monoclonal gammopathy is increasingly recognized as a cause of kidney injury. These renal conditions behave differently than ones without monoclonal gammopathy and require specific treatment. To avoid misdiagnosis, testing for paraprotein should be performed in addition to vasculitis and autoimmune diseases serologies in adults with unexplained AKI or proteinuria. Because the prevalence of monoclonal gammopathy is much more common than glomerular diseases, the nephrotoxicity of the monoclonal protein must be confirmed before cytotoxic therapy is initiated. This can only be done by a kidney biopsy. After a monoclonal gammopathy of renal significant is verified, the evaluation should then focus on the identification of the pathologic clone, because therapy is clone specific. We present this patient to illustrate the clinical presentation of a patient with renal dysfunction and a monoclonal gammopathy. This patient is also used to discuss the diagnostic process in detail when monoclonal gammopathy-associated renal disease is suspected.

Keywords: Acute Kidney Injury; Adult; Humans; MGRS; Paraproteins; glomerular disease; kidney biopsy; multiple myeloma; proteinuria; renal failure.

Copyright © 2016 by the American Society of Nephrology.

Figures

Figure 1.

Classification of monoclonal gammopathy of renal significance–associated nephropathies by ultrastructural characteristics. AIg, immunoglobulin-derived amyloidosis; C, complement; DDD, dense deposit disease; GBM, glomerular basement membrane; LCPT, light–chain proximal tubulopathy; MG, monoclonal gammopathy; MIDD, monoclonal Ig deposition disease; PGNMID, proliferative GN with monoclonal Ig deposits; POEMS, polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes; TMA, thrombotic microangiopathy.

Figure 2.

Light microscopy findings. (A) A representative glomerulus showing global nodular mesangial expansion by sclerosis and Ig deposits with mild mesangial hypercellularity. The nodules are periodic acid–Schiff (PAS) positive. There is segmental duplication of the glomerular basement membrane with cellular interposition (PAS stain). Magnification, ×400. (B) A different glomerulus showing similar nodular mesangial expansion. Some of the nodules stain black on silver stain, whereas others stain pink because of massive Ig deposits. Segmental duplication of the glomerular basement membrane is evident (arrow)(silver stain). Magnification, ×400.

Figure 3.

Immunofluorescence findings. (A–C) There is (A) intense diffuse staining of glomerular mesangium, glomerular basement membranes, tubular basement membranes, and vessel walls for IgG, with negative staining for (B) κ and (C) λ in these locations. (D) There is bright glomerular basement membrane and mesangial staining for IgG1, with weaker focal tubular basement membrane and vessel wall staining for IgG1. Glomeruli were negative for IgG2 and IgG3 and showed only trace staining for IgG4 (not shown). Magnification, ×200 in A and D; ×100 in B and C.

Figure 4.

Electron microscopic findings. (A) Mesangial areas are expanded by abundant fine, granular, powdery, electron–dense deposits. Magnification, ×15,000. (B) Similar deposits are seen segmentally involving the inner aspect of the glomerular basement membranes. Magnification, ×10,000.