Absence of glomerular IgG4 deposition in patients with membranous nephropathy may indicate malignancy

The renal pathological manifestations of malignancy-associated membranous nephropathy (M-MN) and idiopathic membranous nephropathy (I-MN) are similar. It has been suggested that glomerular IgG4 deposition may play an important role in the pathogenesis of I-MN. In the present study, we compared the IgG subclass of immune complex deposition, clinical data and pathological data of patients with M-MN and I-MN. Eight patients with M-MN and 42 patients with I-MN diagnosed between 1997 and 2009 in our hospital were enrolled. The clinical and pathological data were retrospectively collected, and glomerular IgG subclass deposition was detected by immunohistochemistry. Patients with M-MN were older (P = 0.003), with lower serum albumin (P = 0.034) and higher serum C-reactive protein (CRP) level (P = 0.003) than patients with I-MN. The majority of patients with M-MN had earlier pathological stages (P = 0.003) and less IgG deposition in glomeruli (P = 0.029). Absence of IgG4 deposition in glomeruli was notably observed in patients with M-MN (7/8 in M-MN versus 6/42 in I-MN, P < 0.001) and it was an independent predictor for occurrence of malignancy (hazard ratio 0.065, 95% confidence intervals 0.007–0.571, P = 0.014). Absence of glomerular IgG4 deposition, together with older age, severe hypoalbuminemia and high serum CRP level could be useful clues to differentiate M-MN from I-MN.