The urinary excretion of IgG and α1-microglobulin predicts renal outcome and identifies patients deserving treatment in membranous nephropathy

Abstract

To the Editor: In the January 2002 issue of Kidney International Cattran1.Cattran D.C. Membranous nephropathy: Quo vadis (Editorial).Kidney Int. 2002; 61: 349-350https://doi.org/10.1046/j.1523-1755.2002.00125.xAbstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar briefly reviewed the controversy about the treatment of membranous nephropathy (MN). Its variable course underlines the importance of finding an accurate predictor of renal outcome useful to identify the patients who should be treated soon after diagnosis. We recently published a study2.Bazzi C. Petrini C. Rizza V. et al.Urinary excretion of IgG and α1-microglobulin predicts clinical course better than the extent of proteinuria in membranous nephropathy.Am J Kidney Dis. 2001; 38: 240-248Abstract Full Text PDF PubMed Scopus (102) Google Scholar of 78 patients with MN. The urinary excretion of IgG and α1-microglobulin (α1m) was measured in second-morning urine samples and expressed in milligrams per gram of urinary creatinine (mg/g UCr). The excretion of IgG and α1m was significantly associated with the extent of tubulointerstitial damage and predicted the renal outcome in 38 patients with nephrotic syndrome and normal renal function [serum creatinine (SCr ) 0.99 ± 0.22 mg/dL]. Remission was 100% versus 20% in patients with IgG excretion <110 versus ≥110 mg/g UCr (P = 0.0001) and 77% versus 17% in patients with α1m excretion <33.5 versus ≥33.5 mg/g UCr (P = 0.0009), respectively; progression to chronic renal failure (CRF) was 0% versus 35% (P = 0.0026) and 0% versus 58% (P = 0.0001), respectively. Nineteen patients treated with immunosuppressive therapy (steroids and cyclophosphamide on alternate months for 6 months) were compared with 19 untreated patients. There was no difference in remission or progression rate between treated and untreated patients when IgG and α1m excretion was less than the cutoff; a significant difference for progression to CRF between treated and untreated was observed when α1m excretion was greater than the cutoff (17% versus 100%; P = 0.0076). An Editorial comment of Wasserstein3.Wasserstein A.G. The more things change … (Editorial).Am J Kidney Dis. 2001; 38: 405-406Abstract Full Text PDF Scopus (2) Google Scholar stressed that whereas meta-analyses of hundred of patients4.Hogan S.L. Muller K.E. Jennette J.C. Falk R.J. A review of therapeutic studies of idiopathic membranous glomerulopathy.Am J Kidney Dis. 1995; 25: 862-875Abstract Full Text PDF PubMed Scopus (156) Google Scholar,5.Imperiale T.F. Goldfarb S. Bern J.S. Are cytotoxic agents beneficial in idiopathic membranous nephropathy? A meta-analysis of the controlled trials.J Am Soc Nephrol. 1995; 5: 1553-1558PubMed Google Scholar have failed to show a benefit of immunosuppressive treatment on progression, our study has hinted at such a benefit in a mere 38 patients stratified for risk. We suggest that the measurement of urinary excretion of these two proteins maybe a valuable marker of risk, able to predict the renal outcome, and identify the patients who should be treated with immunosuppressive therapy soon after diagnosis.