Clinical characteristics and prognosis of IgA nephropathy and comorbid diabetic kidney disease.

AIMS: This study characterized clinical features, pathology, treatment, and prognosis of biopsy-confirmed coexisting IgA nephropathy (IgAN) and diabetic kidney disease (DKD).

METHODS

This single-centre retrospective study included 80 patients with biopsy-proven IgAN + DKD (2010-2023). Propensity score matching (PSM) (1:1) was used to establish comparable groups of IgAN (n = 80) and DKD (n = 80), matched on age, sex and baseline serum creatinine (sCr). Baseline clinical and pathological data, treatments, 1-year response and long-term outcomes were compared.

RESULTS

In the unmatched cohort, IgAN + DKD patients had higher baseline sCr, greater 24-hour urinary protein (24h-uPro), and less microscopic haematuria (MH) than IgAN. After matching, differences in 24h-uPro and MH persisted. IgAN + DKD showed fewer crescents, lower KM55/IgA ratio, and weaker C3 deposition. Versus DKD, IgAN + DKD had more MH but milder glomerular lesions and arteriolar hyalinosis. In patients with 1-year data (n = 31), 24h-uPro of IgAN+DKD declined substantially, with 58.06% overall clinical remission. Median time free of the composite kidney endpoint (≥50% estimated glomerular filtration rate (eGFR) decline or kidney failure) was 65.63 months; risk was higher than IgAN (HR 2.821, 95% CI 1.174-6.781) but lower than DKD (HR 0.525, 95% CI 0.293-0.943). Baseline sCr and irreversible GBM thickening associated with endpoints. Unselected immunosuppression showed no long-term renal benefit.

CONCLUSIONS

IgAN + DKD exhibited lower intrarenal immune activity than IgAN and less severe diabetic glomerular injury than DKD. The KM55/IgA ratio might aid differentiation from IgAN. Long-term renal prognosis was intermediate between the monodisease groups. Routine immunosuppression reduced short-term proteinuria but did not improve hard renal endpoints. Higher baseline sCr and GBM thickness linked to poorer outcomes.