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We have observed a predominantly mesangial non-immunoglobulin A immune complex mesangial glomerulopathy (MG) in renal transplants with mesangial deposits by immunofluorescence and electron microscopy. Clinicopathological features of 28 patients with MG were analyzed and compared with 28 transplant controls, matched for age, sex, ethnicity, donor type, estimated glomerular filtration rate, and interval from transplant to biopsy. Indications for biopsy in the MG group were allograft dysfunction in 64%, allograft dysfunction/proteinuria in 29%, and proteinuria in 7%. Biopsy indications in controls were allograft dysfunction (61%), allograft dysfunction/proteinuria (18%), proteinuria (14%), and delayed graft function (7%). Most MG cases had mild mesangial hypercellularity with endocapillary proliferation in 2 and crescents in 2 without fibrinoid necrosis. Immunoglobulin M-dominant deposits were present in 83%, and immunoglobulin G was dominant in 17% with mesangial deposits in 93% of cases by electron microscopy. Compared with controls, MG had higher Banff interstitial inflammation score (i) (P = .036) and was associated with concurrent acute T-cell-mediated rejection (P = .023), but not with acute or chronic antibody-mediated rejection. MG patients and controls had similar prevalence of polyomavirus nephropathy and Epstein-Barr virus infection. At follow-up, most MG patients had stable estimated glomerular filtration rate with no or stable proteinuria. Disease-specific graft survival was not different in MG versus controls. We conclude that, in view of the apparent self-limited nature of this lesion, additional treatment may not be required in these patients. Awareness of this lesion may thus spare patients unwarranted further intervention., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Glomerulonephritis (GN) characterized by immune complex deposits typical of postinfectious GN but with a paucity or absence of overt clinical symptoms and/or urinary abnormalities may occur after a group A streptococcus infection. The overall incidence of this type of subclinical GN is not known. To address this question, electron microscopy findings in 1012 consecutive renal biopsy specimens (952 native kidney, 60 transplant) examined by a single renal pathologist from August 1999 to April 2002 were retrospectively reviewed for the presence of distinct subepithelial and intramembranous deposits indicative of postinfectious GN. Such deposits were noted in 83 biopsy specimens, including 26 with a primary diagnosis of postinfectious GN (acute, persistent, or latent) and 57 in which these deposits were an incidental finding. In each of the latter 57 cases, some or all of the deposits showed partial or extensive loss of electron density typical of partially or largely resorbed deposits. A diagnosis of incidental postinfectious GN was not made in any biopsy specimen exhibiting another immune complex-related glomerular disease that could possibly account for the deposits, composing 443 of the 1012 biopsy specimens examined. Thirty of the 57 biopsy specimens with incidental postinfectious GN showed mesangial hypercellularity, although this was focal and segmental in all but 3 cases and was not accompanied by the endocapillary hypercellularity typical of acute postinfectious lesions. Immunofluorescence microscopy revealed glomerular deposits of C3 in >90% of these biopsy specimens and IgM deposits in 66%, but only rare IgG, IgA, and Cq deposits. Twenty-three (40%) of these 57 biopsy specimens exhibited diabetic nephropathy, either alone or in combination with another lesion; for perspective, only 128 (13%) of the 1012 biopsy specimens examined showed evidence of diabetic nephropathy. In summary, incidental evidence of resolving or largely healed postinfectious GN was noted in up to 10.5% of renal biopsy specimens (57 of 543, not including specimens with a primary diagnosis of an immune complex-related glomerular disease). The recognition of such lesions is potentially important in the interpretation of certain renal biopsy specimens., (Copyright 2003, Elsevier Science (USA). All rights reserved.)