Focal segmental glomerulosclerosis in mild IgA nephropathy: a clinical-pathologic study.

Background: The significance of focal segmental glomerulosclerosis (FSGS) in mild IgA nephropathy is uncertain.

Methods: All consecutive renal biopsies performed between 1996 and 2005 in adults with a diagnosis of mild IgA nephropathy (Lee Grade 1 or 2) at St Paul's Hospital, Vancouver, Canada, were reviewed.

Results: Seventy-five patients were included, 26 (35%) with IgA nephropathy and FSGS (FSGS+ group) and 49 (65%) with IgA nephropathy without FSGS (FSGS- group). The mean follow-up was 3 years. At the time of renal biopsy the FSGS+ group had a lower eGFR (60 versus 73 mL/min, P = 0.02), lower serum albumin (38 versus 41 g/L, P = 0.02), higher mean arterial pressure (103 versus 97 mmHg, P = 0.03) and greater protein excretion (3.0 versus 1.3 g/day, P < 0.01) than the FSGS- group. On histology, the FSGS+ group had a higher percentage of obsolete glomeruli (23.4% versus 12.7%, P < 0.01), and 31% of FSGS+ biopsies had >or=25% tubular atrophy/interstitial fibrosis while this was not observed in the FSGS- group (P < 0.01). The primary outcome measure, DeltaGFR, was -2.56 mL/ min/year in the FSGS+ group and +1.14 mL/min/year in the FSGS- group, difference: 3.70 mL/min/year (P = 0.03) (univariate). In the multivariate model, the FSGS+ group declined at 0.19 mL/min/year (-14.16, 13.78) and the FSGS- group improved at 2.85 mL/min/year (-11.64, 17.34), difference 3.04 mL/min/year, P = 0.18.

Conclusions: Our study suggests that the focal segmental glomerulosclerosis lesion and associated clinical and pathologic findings in patients with mild IgA nephropathy are associated with a worse renal outcome.