Abstract
AIM: To characterize the epidemiology, clinicopathological features, and renal outcomes in patients with Monoclonal Gammopathy of Renal Significance (MGRS). METHODS: The authors conducted a retrospective analysis of all renal biopsy-confirmed MGRS cases diagnosed between 2010‒2020, with histopathological review by two independent pathologists. Post-hoc power analysis confirmed adequate statistical power (92 %). RESULTS: Among 124 histologically confirmed MGRS cases (median age 64.0-years, IQR 52.5‒68.0), renal amyloidosis predominated (75.8 %), followed by monoclonal immunoglobulin deposition disease (MIDD, 10.5 %), cryoglobulinemic GN (4.8 %), proliferative GN with monoclonal Ig deposits (PGNMID, 2.4 %), light chain proximal tubulopathy (3.2 %), and C3 glomerulopathy with monoclonal gammopathy (1.6 %). Amyloidosis patients primarily presented with nephrotic syndrome (77.7 %), while fewer exhibited acute kidney injury (3.2 %), chronic kidney disease (16.1 %), or ESRD (6.7 %). Compared to other MGRS subtypes, amyloidosis patients demonstrated significantly lower anemia rates (p < 0.001), higher LDH (p = 0.035), preserved eGFR (p < 0.001), greater proteinuria (p = 0.037), and hypoalbuminemia (p < 0.001). The renal response rates were 26.1 % (Amyloidosis-Associated MGRS, MGRS-A) versus 33.3 % (Non-Amyloidosis MGRS, MGRS-NA), while hematologic responses were 8.7 % versus 0 %, respectively. Both hematologic (p = 0.007) and renal responses (p = 0.009) correlated with improved survival. MGRS-A showed inferior renal survival (p = 0.05). Multivariate analysis identified hypotension (p = 0.005), elevated creatinine (p = 0.002), and cardiac involvement (p = 0.022) as independent predictors of ESKD, while age (p < 0.001) and cardiac involvement (p < 0.001) predicted mortality. CONCLUSION: MGRS represents a clinically significant cause of kidney injury in monoclonal gammopathy patients, with amyloidosis being the predominant etiology. MGRS-A portends a worse prognosis than MGRS-NA. Therapeutic responses in both hematologic and renal parameters predict survival benefits. Age and cardiac involvement emerge as key prognostic markers for both renal and patient survival.