Objective To explore the relationship between serum immunoglobulin G (IgG) and clinicopathologic features and prognosis of patients with idiopathic membranous nephropathy (IMN).

Methods A retrospective cohort study was conducted on 284 inpatients with IMN who underwent renal puncture biopsy in the Department of Nephrology, the First Affiliated Hospital of Guangxi Medical University from July 2012 to July 2020. At least 12 months of follow-up, progression of renal function was the renal endpoint event. According to the serum IgG level, they were divided into decreased IgG group (< 8.0g/L) and normal IgG group (≥8.0g/L).

Results In this study, 284 cases of IMN were included, including 222 cases in the decreased IgG group and 62 cases in the normal IgG group. About 78.2% of the patients had serum IgG lower than the normal value. The median follow-up time was 31.15 months, and a total of 44 cases (15.5%) developed renal function. Compared with the normal IgG group, the proportion of male, proportion of macroalbuminuria, proportion of medium-risk patients, serum creatinine, total cholesterol, triglyceride, low density lipoprotein, and 24-hour urinary protein in the decreased IgG group were higher, while age, the proportion of low-risk patients, levels of serum albumin, IgA, IgM and complement C3 were lower (all P < 0.05). Kaplan-Meier survival analysis indicated that the kidney survival rate in the IgG reduced group was lower than that in the IgG normal group. COX regression analysis suggested that serum IgG decline was still an independent risk factor for renal function progression in IMN patients after adjusting for confounding factors (P < 0.05).

Conclusion Serum IgG is an important factor affecting renal function progression in IMN patients, and the decrease of serum IgG is associated with poor renal prognosis in IMN patients.