Outcome of Idiopathic Membranous Nephropathy: A Retrospective Study.

Background: Idiopathic membranous nephropathy (IMN) is one of the most common causes of nephrotic syndrome (NS) in Caucasian adults. Most patients have good renal prognosis, but 30-40% may progress to end stage renal disease (ESRD).

Objectives: To evaluate the efficacy and safety of immunosuppressive treatment (IST) in high-risk patients.

Methods: All IMN patients diagnosed by kidney biopsy from 2004-2010 were included. Clinical and laboratory data were collected at each follow-up visit. Risk assessment for renal progression classified patients as high risk if: 24 hour protein excretion > 6 g/day, estimated glomerular filtration rate (eGFR) < 60 ml/min/1.73 m2, and severe disabling or life-threatening clinical symptoms of NS were present.

Results: Among 290 biopsies, 37 patients (12.7%) were IMN. They were allocated to the high-risk IST group (n=16) or low-risk supportive treatment (ST) group (n=21) according to the likelihood of developing renal failure. Mean follow-up was 47 ± 17.3 months. Complete and partial remission rate was 68.7% for high-risk IST vs. 90.4% for low-risk ST. In the high-risk IST group, eGFR was significantly lower at 30 months (65.5 ± 28.6 vs. 85.3 ± 21.6 at baseline, P < 0.05). Four high-risk patients reached ESRD. In the low-risk ST group, eGFR remained stable at 30 and 60 months.

Conclusions: This study showed a high remission rate for IMN. IST with prednisolone and cyclophosphamide provided favorable renal outcomes in most high-risk patients. The very high remission rate obtained in the low-risk patients confirms the adequacy of supportive treatment in this group.