KL CHOW1, J RYAN1,2
1Department of Nephrology, Monash Medical Centre, Clayton, VIC, Australia; 2Department of Medicine, Monash University, Clayton, VIC, Australia
Background and Aim: Emerging literature suggests that monoclonal gammopathy of undetermined significance (MGUS) is associated with a wide spectrum of renal pathology. The reported prevalence of MGUS in the general population is 3.2% over 50y (5.3% over 70y, 7.5% over 85y). We sought to characterise the prevalence of monoclonal gammopathy in a cohort of patients from Monash Health undergoing diagnostic renal biopsy and examine patterns of renal disease.
Methods: 558 patients undergoing diagnostic native renal biopsy at Monash Health from July 2010 until May 2016 were included in the audit. Of those, 271 had a serum protein electrophoresis or free light chain assay within 12 months of the biopsy. 19 patients with known myeloma, or with myeloma or amyloid found on biopsy, as well as 3 patients with hepatitis C associated cryoglobulinemia were excluded.
Results: Overall 45/249 patients (18.1%) had an abnormal electrophoresis or free light chain result. The distribution of MGUS related to biopsy diagnosis was as follows: Diabetes 9/30 (30%), Hypertension 7/33 (21%), Minimal Change/Thin Membrane 0/13 (0%), ANCA 3/21 (14%), IgA Nephropathy 1/40 (3%), Membranous 3/26 (12%), Primary Focal Segmental Glomerulosclerosis 3/13 (23%), Systemic Lupus Erythematosus 2/13 (15%), Thrombotic Microangiopathy 3/3 (100%), Cryoglobulinemia 2/3 (67%), and Other 12/54 (22%). 24/45 (53.3%) had a conventional MGUS, while 21/45 (46.7%) had only an abnormal free light chain assay. As expected, the rate of MGUS rose with age: <45yrs 2/71 (2.8%), 45–65yrs 19/98 (19.4%) and >65yrs 24/80 (30%) (p<0.0001).
Conclusions: Prevalence of MGUS was much higher in this population of patients undergoing diagnostic renal biopsy than previously reported in the general population, supporting the possible association between MGUS and renal disease.