Re-evaluation of the prognosis of patients with IgA nephropathy and mild proteinuria: a longitudinal study with unexpected results

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide and a major cause of chronic kidney disease. Mild proteinuria (< 0.5 g/24 h) is generally considered to indicate a favorable prognosis in IgAN. This study aimed to explore the clinicopathological features and prognostic factors of such patients. We performed a retrospective analysis of IgAN patients who had renal biopsies at our hospital from 2008 to 2023. We included patients with 24-hour proteinuria < 0.5 g, age ≥ 15 years, and follow-up ≥ 12 months. Risk factors were assessed using logistic regression and Cox proportional hazards models. Over a mean follow-up of 90.75months, 27 patients(10.19%) experienced endpoint events. The overall eGFR slope was − 2.07mL/min/1.73 m 2 per year. Greater eGFR decline correlated with lower 10-year renal survival. Multivariate analysis showed severe tubulointerstitial damage, lower baseline eGFR and steeper eGFR decline were independent risk factors for renal endpoint events. Renal arteriolar lesions, lower baseline eGFR, steeper eGFR decline, and lower TyG-BMI were risk factors for poor renal prognosis. Our study challenges the assumption that IgAN patients with mild proteinuria have a favorable prognosis. Over 90.75 months, 10.19% of patients experienced endpoint events, with an eGFR decline of 2.07 mL/min/1.73 m 2 per year. These findings indicate significant disease progression risk in IgAN patients with mild proteinuria. In addition to traditional risk factors, metabolic factors such as TyG-BMI are important prognostic predictors.