Glomerulonephritis - Proliferative Glomerulonephritis with Monoclonal IgG deposits

An interesting factoid that I had drummed into my head today by Sanjeev Sethi while we were both participating in a renal conference in Delhi: among the wide spectrum of dysproteinemic kidney disease don't forget proliferative glomerulonephritis with monoclonal IgG deposits. The classic paper was published by Samih Nasr and colleagues from Columbia University, College of Physicians & Surgeons in JASN 2009 (it is available open access).

They retrospectively identified 37 patients. Key features of the patients:

1. most  were white (81%), female (62%), or older than 50 yr (65%). 
2. 49% had nephrotic syndrome, 68% had renal insufficiency, and 77% had hematuria. 
3. 30% of the patients, they identified a monoclonal serum protein with the same heavy- and light-chain isotypes as the glomerular deposits (mostly IgG1 or IgG2), but only one patient had myeloma. 
4. Histologic patterns were predominantly membranoproliferative (57%) or endocapillary proliferative (35%) with membranous features. Electron microscopy revealed granular, nonorganized deposits, and immunofluorescence demonstrated glomerular deposits that stained for a single light-chain isotype and a single heavy-chain subtype, most commonly IgG3κ (53%).
5. During an average of 30.3 mo of follow-up for 32 patients with available data, 38% had complete or partial recovery, 38% had persistent renal dysfunction, and 22% progressed to ESRD. 
6. On multivariate analysis, higher percentage of glomerulosclerosis was the only independent predictor of ESRD. 

The point that Sanjeev Sethi from the Mayo clinic made was that although the predominant monoclonal Ig that Nasr and colleagues identified was IgG3 kappa he has seen it proliferative GN with other monoclonal Ig's.