Clinicopathological spectrum and outcomes of monoclonal gammopathy of renal significance: A renal biopsy-based study

Background: Monoclonal gammopathy of renal significance (MGRS) comprises renal lesions caused by nephrotoxic monoclonal immunoglobulins produced by small B-cell/plasma-cell clones without overt hematological malignancy. Renal biopsy is essential for diagnosis and characterization. Aims and Objectives: This study aimed to determine the prevalence and histomorphological spectrum of MGRS among renal biopsies and assess clinical outcomes. Materials and Methods: This retrospective and prospective renal biopsy-based study was conducted at the Department of Pathology, Sanjay Gandhi Postgraduate Institute of Medical Sciences. Biopsies from January 2012 to March 2021 were evaluated using light microscopy, immunofluorescence, and electron microscopy where available. Clinical outcome data were analyzed using statistical tests; P<0.05 was considered significant. Results: Among 7717 renal biopsies, 109 were diagnosed as monoclonal gammopathy-associated kidney disease, of which 62 fulfilled criteria for MGRS, yielding a prevalence of 0.8%. The mean age was 55.6±10.7 years, with male predominance (M=1.8:1). AL amyloidosis was the most common lesion (34; 54.8%), followed by monoclonal immunoglobulin deposition disease (12; 19.3%), fibrillary glomerulonephritis (5; 8.0%), and proliferative glomerulonephritis with monoclonal immunoglobulin deposits (4; 6.4%). Other lesions included light chain proximal tubulopathy, C3 glomerulonephritis, membranous nephropathy, and acute tubulointerstitial nephritis. Among 52 patients with follow-up data, mean follow-up duration was 13.8±17.3 months; 18 (35%) became dialysis-dependent, and 34 (65%) died. No significant differences were found between the AL and non-AL groups for age, dialysis dependence, or mortality. Conclusion: MGRS was uncommon but clinically important, with considerable morbidity and mortality. AL amyloidosis predominated. Early biopsy-based diagnosis and multidisciplinary nephrology and hematology evaluation are essential for timely management and better outcomes.