Burden and correlates of anemia in IgA nephropathy versus other primary glomerulonephritides

BACKGROUND: Anemia is a frequent but often underrecognized complication of primary glomerulonephritis (PGN). This study aimed to determine the prevalence and determinants of anemia in a large multicenter PGN cohort, with particular focus on immunoglobulin A nephropathy (IgAN), and to evaluate its clinical, laboratory, and histopathological correlates. METHODS: Data were retrieved from the Turkish Society of Nephrology Glomerulonephritis Database (TSN-GOLD). A total of 5,500 patients with biop-valuesy-proven PGN were included, of whom 1,571 (28.6%) had IgAN. Demographic, clinical, laboratory, and histopathological findings were analyzed. Anemia was defined according to World Health Organization criteria. Multivariate logistic regression was used to identify independent risk factors for anemia. RESULTS: The prevalence of anemia was approximately 35% in both the overall PGN cohort and the IgAN subgroup. Patients in the lowest hemoglobin tertile (< 11.8 g/dL) were older, had lower eGFR, serum albumin, and total protein, as well as higher serum creatinine, urea, and inflammatory markers. Histologically, mesangial hypercellularity, interstitial inflammation, and particularly tubular atrophy/interstitial fibrosis (T1-T2) were more common in this group. Multivariate analysis identified older age, female sex, lower eGFR, hypoalbuminemia, and advanced tubular atrophy as independent risk factors for anemia. Importantly, PGN subtype was also an independent determinant: compared with IgAN, membranoproliferative GN carried a markedly higher anemia risk, whereas minimal change disease and focal segmental glomerulosclerosis showed lower risk. CONCLUSIONS: Anemia is a common and clinically relevant comorbidity in PGN, strongly associated with both functional and structural renal impairment. Beyond reduced kidney function, disease-specific mechanisms contribute to anemia in IgAN, including chronic low-grade inflammation and recurrent hematuria. Recognition of PGN subtype as an independent determinant underscores the need for tailored evaluation and management of anemia in these patients. TRIAL REGISTRATION: This study was registered retrospectively in an appropriate clinical trial registry.