Renal Involvement and Outcome In Monoclonal Lightchain Disease
Authors: Bergner Raoul , Uppenkamp Michael J. , Hoffmann Martin 
Published: October 2019

Abstract
Abstract 4985

Background:
Renal involvement is very common in monoclonal light chain disease (mLCD). However, the types of renal disease are manifold. Also the prognosis and outcome is very different. We analysed the data and renal outcome of patients with monoclonal light chain disease and renal disease.

Methods:
We analysed the data of patients with monoclonal light chain disease, who underwent a kidney biopsy due to proteinuria and/or renal insufficiency of unclear origin, retrospectively. Data of renal function, proteinuria, the type of renal disease and the renal outcome were collected. The mLCD were subclassified in multiple myeloma (MM), AL-amyloidosis (ALA), monoclonal gammopathy of unclear significance (MGUS) and B-cell non hodgkin lymphona (B-NHL). The kidney biopsy findings were classified in cast nephropathy (CN), ALA, light chain deposit disease (LCDD) and other renal disease (ORD).

Results:
88 patients were included in the analysis. 47 patients suffered from MM, 15 from systemic ALA, 21 from MGUS and 5 from B-NHL, respectively. In 17 patients the mLCD was not known before kidney biopsy but detected by typical kidney disease. Of the 47 patients with MM 24 had CN, 4 LCDD, 4 ALA and 15 ORD, respectively. All patients with ALA had renal amyloidosis except one, who had an IgA-glomerulonephritis. All patients with MGUS suffered from ORD only. Patients with B-NHL had CN one patient, LCDD one patient, ALA one patient and ORD two patients, respectively.
The ORD were also associated with the mLCD in 21 cases (interstitial nephritis n=7, nephrocalcinosis n=7 and membranoproliferative glomerulonephritis n=4), the other patients had kidney disease independent from mLCD (e.g. diabetic nephropathy, focal segmental glomerulosclerosis, IgA-glomerulonephritits or nephroangiosclerosis). The mean follow up time was 20.4±24.8 month.
Patients with CN had a significant worse renal function at time of kidney biopsy [serum creatinine [mg/dl]: CN 4.7±4.0; LCDD 3.36±1.38; ALA 1.46±1.0; ORD 2.0±2.3; p< 0.001 CN vs. ALA and ORD]. Patients with ALA had a significant greater proteinuria [g/d], than the other patients [CN 3.3±2.5; LCDD 1.7±0.9; ALA 5.6±5.2; ORD 2.1±1.9; p< 0.05 ALA vs. LCDD and CN; p<0.001 ORD vs. ALA].
3.7 months after kidney biopsy 50% of patients with CN were on dialysis (HD). At 12 month 59% of patients with CN were on HD, compared to 37% of patients with ALA, 20% of patients with LCDD and 8% of patients with ORD (p=0.0004). Patients on HD had a significant worse survival compared to those without HD [50% survival 5.3 vs. 42 months; p=0.005].

Discussion:
Our data demonstrate, that not all patients with mLCD suffered from a mLCD associated renal disease. The renal prognosis was very different between the types of renal disease. The worst renal outcome had patients with CN followed by patients with ALA. The best renal outcome had patients with ORD. Once on HD the survival is worse than without HD. Based on our data we would recommend to clarify the exact type of renal disease in all patients with mLCD and any evidence of renal disease by kidney biopsy.

Disclosures:
No relevant conflicts of interest to declare.