Vincenzo Sepe*,Paolo Albrizio,Antonio Dal Canton
Introduction: Since 1989 when Kusunoki et al. described C4d renal deposits in native idiopathic membranous nephropathy (nIMN) their role in disease progression has not been clarified yet. Recent studies have identified C4d glomerular staining as a marker of negative progression of renal function in a primary glomerular disease like IgA nephropathy. We have retrospectively analysed 15 consecutive formalin-fixed paraffin-embedded kidney biopsies from patients with nIMN (7F, 8M) performed in our Unit from October 1995 to February 2011.
Methods: Kidney sections were stained using polyclonal rabbit IgG anti-human C4d antibodies. Normal renal tissue was obtained from heart-beating braindead donors before kidney harvesting. Positive control biopsy was a humoral kidney rejection with intense C4d staining. Data are expressed as M ± SD.
Results: Ten (5F, 5M) of 15 nIMN kidney biopsies showed global and diffuse C4d glomerular capillary staining (C4d+). At 6-month follow-up (C4d+ 31 ± 26 months, C4d– 29 ± 31 months; P = NS) we observed a significantly higher 24-hour urinary protein excretion rate (UPr) in C4d+ (P = 0.0051 vs. C4d–), and a significantly lower MDRD eGFR (P = 0.0337 vs. C4d– at diagnosis) when compared with data at disease presentation.
Conclusion: Our data suggest that C4d glomerular capillary deposits in nIMN with a follow-up longer than 6 months might be a negative prognostic factor for both UPr and eGFR. We are aware that our study has limitations like the relatively short term follow-up and the little number of biopsy analysed. Nevertheless, the association between increasing UPr, worsening of renal function and glomerular deposits of C4d in nIMN patients might deserve reporting and eventually confermation by further investigations.
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