Monoclonal Immunoglobulin-Associated Renal Lesions in Patients with Newly Diagnosed Multiple Myeloma: A Report from a Single Center

BACKGROUND: Monoclonal immunoglobulin-associated renal lesions in patients with newly diagnosed myeloma vary. We aimed to determine the pathological spectrum and analyze associated prognostic factors. METHODS: Fifty-six patients with newly diagnosed multiple myeloma and biopsy-proven renal lesions were enrolled. Kidney biopsies were reanalyzed, and the baseline clinical characteristics, treatments and outcomes were recorded. RESULTS: Fifty-one patients had monoclonal immunoglobulin-associated renal lesions, with myeloma cast nephropathy (MCN) being the most common pattern. We divided our cohort into pure MCN, MCN+ other pathologies and non-MCN. Patients with MCN had more severe renal injury than those with non-MCN. In our cohort, none of the patients with pure MCN or MCN + other pathologies presented with nephrotic syndrome. Patients with non-MCN had better renal and overall survival than those with pure MCN but similar survivals to those with MCN + other pathologies. Number of myeloma casts (HR 1.08, p = 0.012) was the only independent prognostic factor for renal survival. Male sex (HR: 3.64; p = 0.015) and number of casts (HR: 1.17; p = 0.001) were independent prognostic factors for overall survival. CONCLUSION: Patients with MCN had more severe renal injury than those with non-MCN. Patients with non-MCN had better renal and overall outcomes than those with pure MCN, but their outcomes were similar to those with MCN + other pathologies. The independent predictors of overall survival were male sex and number of myeloma casts.