Focal segmental glomerulosclerosis is not a sufficient predictor of renal outcome in patients with membranous nephropathy

Background. The course of idiopathic membranous nephropathy (iMN) is variable in untreated patients. Accurate prediction of renal outcome would allow optimal treatment decisions. We demonstrated that urinary beta 2-microglobulin (beta 2M) predicted prognosis in iMN with high sensitivity and specificity. It has been suggested that focal segmental glomerulosclerosis (FSGS) is a discriminative parameter with independent prognostic value. Methods. We selected patients with iMN biopsied between 1988 and 2002. Biopsies were analysed for the presence of FSGS, interstitial fibrosis and vascular lesions. Serum creatinine, creatinine clearance, proteinuria and blood pressure were recorded at baseline. Outcome variables included remission of proteinuria, renal death (RD) defined as serum creatinine > 135 pmol/l or increase of serum creatinine of > 50%, or end-stage renal disease (ESRD). In a subgroup of patients, urinary beta 2-microglobulin (beta 2M) was measured. Results. We included 53 patients (33M, 20F). Mean age was 51 years, serum creatinine 99 pmol/l, and proteinuria 7.0g/10mmol creatinine. FSGS was present in 22 patients. These patients were characterized by a higher serum creatinine at time of biopsy (P = 0.035), more severe interstitial fibrosis (P = 0.001) and higher stage of membranous nephropathy (P = 0.00 1). During follow-up 24 patients developed RD, almost equally distributed between patients with and without FSGS. Renal survival was numerically, but not significantly, lower in patients with FSGS. In Cox proportional hazard analysis, only serum creatinine at the time of biopsy was an independent predictor of RD or ESRD (P < 0.00 1). In patients with known urinary beta 2M, there was no significant correlation with FSGS score (P = 0.174). Conclusion. FSGS is not an accurate prognostic marker in iMN. Histological scoring of FSGS is inferior to measurement of urinary proteins in predicting renal outcome in iMN.