Background: Idiopathic membranous nephropathy (IMN), a common cause of nephrotic syndrome in adults, is usually treated by combination of corticosteroids with cytotoxic drugs. In cases resistant to this regimen, the use of cyclosporin A (CsA) is followed by frequent remissions of the nephrotic syndrome.
Aim: The purpose of this study was to estimate the effectiveness of prednisolone and small doses of CsA as first-line treatment of nephrotic patients with IMN, in relation to the progression of the disease, based on functional and histological changes.
Patients and methods: Sixteen patients, with nephrotic syndrome due to IMN and well-preserved renal function, were treated with prednisolone (starting dose: 0.5 mg/kg bw/day) and CsA (starting dose: 3 mg/kg bw/day) for 24 months. A repeat renal biopsy was performed after 18 months of treatment in 10 patients with remission of nephrotic syndrome, to estimate the activity of the disease and to identify any features of CsA toxicity.
Results: Remission of the nephrotic syndrome was observed in 14 out of 16 patients after 5 +/- 2 months of treatment. Complete remission was observed in 8 and partial remission in 6 patients (urinary protein was reduced from 6.9 +/- 3.4-0.2 +/- 0.06 g/24 h and 1.2 +/- 1.0 g/24 h, respectively, p < 0.01). The renal function was well preserved in 13 out of 16 patients over a 24-month period of treatment. Deterioration of renal function was observed in 3 patients (creatinine clearance reduced from 86 +/- 21-37 +/- 17 ml/min, p < 0.05) who had either persistent nephrotic syndrome or frequent relapses. Relapses of the nephrotic syndrome were observed in 5 of 14 patients. Repeat renal biopsies showed that glomerular sclerosis, tubulointerstitial injury, vascular hyalinosis and stage of the disease were deteriorated in most patients. Isometric vacuolization of tubular epithelial cells was observed in 2 of 10 patients.
Conclusion: IMN nephrotic patients treated with prednisolone and low doses of cyclosporin A showed a high remission rate of nephrotic syndrome. However, progression of chronic histological lesions was found in repeat renal biopsies. This suggests that cyclosporin can frequently induce remission of nephrotic syndrome in IMN patients, but even low doses of the drug are not free of potential renal toxicity.