Clinicopathological characteristics and outcomes in patients with diabetic nephropathy coexisting idiopathic membranous nephropathy: a retrospective observational study

Diabetic nephropathy frequently coexists with membranous nephropathy (MN), yet their combined clinical characteristics and prognosis remain poorly understood. We retrospectively analyzed 276 patients with biopsy-confirmed kidney disease from 2015 to 2023, including 34 patients with diabetic nephropathy and MN (DN-MN), 44 diabetes mellitus combined with MN (DM-MN), and 198 MN patients. Clinical manifestations, pathological characteristics, treatment regimens, and outcomes were compared among the three groups, and a nomogram to predict renal complete remission (CR) was constructed. At baseline, patients with DN-MN had worse renal function than the other groups. Median estimated glomerular filtration rate (eGFR) was 68.2 (41.7-104.8) mL/min/1.73 m² in the DN-MN group, compared with 100.3 (91.4-112.1) mL/min/1.73 m² in the DM-MN group and 101.4 (89.2-113.0) mL/min/1.73 m² in the MN group (<i>p</i> < 0.001). During 26.0 months (Interquartile Range: 17.5-40.0 months) follow-up, when renal CR was defined as the endpoint, 7 patients (20.6%) with DN-MN, 21 (47.7%) with DM-MN, and 94 (47.5%) with MN achieved CR. Pathological features including glomerular segmental sclerosis, interstitial fibrosis and tubular atrophy, and segmental mesangial proliferation were identified as factors associated with renal complete remission. Notably, both DN-MN and DM-MN patients showed comparable rates of renal complete remission between the glucocorticoid and non-glucocorticoid groups in this cohort. These findings indicate that DN-MN patients exhibit worse renal function, more severe pathological lesions, and poorer prognosis than DM-MN and MN patients, with chronic renal pathological lesions serving as important prognostic factors.