Unmasking Renal Function Similarities in Gammopathies: Comparative Evaluation of Glomerular, Tubular, and AKI Parameters.

Abstract

Renal impairment is a well-recognized complication of plasma cell dyscrasias such as multiple myeloma; however, its onset and extent in earlier gammopathy states remain uncertain. Monoclonal gammopathy of undetermined significance (MGUS) represents a premalignant c o n d i t i o n , w h e r e a s p o l y c l o n a l hypergammaglobulinaemia (PHGG) reflects a reactive immune process. This study investigated renal functional differences between MGUS and PHGG using glomerular, tubular, and early acute kidney injury (AKI) biomarkers. Patients were categorized by serum protein electrophoresis and free light chain (FLC) assays. Renal evaluation comprised estimated glomerular filtration rate (eGFR), serum creatinine (sCr), urinary neutrophil gelatinase-associated lipocalin (uNGAL), NGAL-to-creatinine ratio, tubular reabsorption of phosphate (TRP), maximum phosphate reabsorption per GFR (TmP/GFR), and fractional sodium excretion (FeNa). Statistical analyses compared renal indices, assessed correlations, and identified predictors of renal function. MGUS patients were generally older and predominantly male, while PHGG was more common among individuals with chronic infections. No significant differences were observed between the two groups across glomerular, tubular, or AKI markers (p > 0.005) in all. Although ê-FLC showed weak associations with subtle renal stress indicators, multivariate regression revealed that male gender—not gammopathy type—was the strongest predictor of reduced eGFR. MGUS and PHGG exhibited comparable renal functional profiles, with no evidence of distinct glomerular, tubular, or AKI biomarker signatures differentiating the groups. These findings suggest that renal impairment in MGUS does not occur at the early stage of disease but may emerge with progression or additional renal insults.