Spectrum of renal involvement in MGRS patients: a 6-year study

Summary Background and objectives Monoclonal gammopathy of renal significance (MGRS) includes smoldering B cell or plasma cell clones causing renal disease. Our understanding of MGRS is still evolving and through our study we intend to analyze the spectrum of renal involvement in patients with MGRS in our institution in the last 6 years. Materials and methods All patients admitted to our hospital with a diagnosis of MGRS from November 2015 to October 2021 were reviewed. It was a retrospective observational study. History, physical examination, and laboratory investigations were meticulously documented. Results During the 6 year study period, 108 patients with monoclonal gammopathy of unknown significance (MGUS) were diagnosed, with 29 (26.85%) of them developing MGRS. Median age of the patients was 55 years with majority being men. On light microscopy, the most common renal biopsy patterns were AL amyloidosis (11 patients), monoclonal immunoglobulin deposition disease (6 patients) followed by proliferative glomerulonephritis with monoclonal IgG deposits in 5 patients. Conclusions During the 6 year study period, 108 patients with MGUS were diagnosed, with 29 (26.85%) of them developing MGRS. Serum immunoelectrophoresis was the most sensitive test for paraprotein detection in our study. IgG kappa and IgG lambda were the most common paraprotein patterns on serum immunofixation. On renal biopsy, AL amyloidosis-lambda was the most common, followed by monoclonal immunoglobulin deposition disease and proliferative glomerulonephritis with monoclonal IgG deposition. Serum creatinine and paraprotein measured by the serum-free light chain (SFLC) ratio had a positive correlation (statistically significant). There was no correlation between urine protein creatinine ratio and M protein measured by serum protein electrophoresis (SPEP) or SFLC ratio in MGRS patients. We conclude by saying that in case of suspicion of MGRS, renal biopsy should be considered.