© 2020 International Society of Nephrology Introduction: Glomerular diseases are characterized by variable disease activity over many years. We aimed to analyze the relationship between clinical disease activity and duration of glomerular disease. Methods: Disease activity in adults with chronic minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and IgA nephropathy (IgAN; first diagnostic biopsy >5 years before enrollment; Of Longstanding Disease [OLD] cohort, n = 256) followed at Columbia University Medical Center (CUMC), was compared with disease activity of an internal and external cohort of patients with first diagnostic biopsy <5 years before enrollment drawn from the Cure Glomerulonephropathy Network (CureGN cohort, n = 1182; CUMC-CureGN cohort, n = 362). Disease activity was defined by (i) Kidney Disease: Improving Global Outcomes–recommended threshold criteria for initiation of immunosuppression in primary glomerulonephropathy (GN) and (ii) CureGN's Disease Activity Working Group definitions for activity. Results: No significant differences were detected among the 3 cohorts in terms of age, sex, serum creatinine, and urinary protein-to-creatinine ratio. For each GN subtype, disease activity in the OLD cohort was comparable with disease activity in the entire CureGN and the CUMC-CureGN cohort. When limiting our comparisons to disease activity in incident CUMC-CureGN patients (first diagnostic biopsy within 6 months of enrollment), OLD patients demonstrated similar activity rates as incident patients. Conclusion: Disease activity did not differ among patients with shorter versus longer duration of disease. Such survivor patients, with long-term but persistent disease, are potentially highly informative for understanding the clinical course and pathogenesis of GN and may help identify factors mediating more chronic subtypes of disease.
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