Membranoproliferative Glomerulonephritis and Less Characterized Etiological Factors.
Shashank Cheemalavaagu, Sang H Woo, Ajit Mahapatra, Neeraja Kambham. Stanford University, CA; Kaiser Permanente, Santa Clara
Background: Membranoproliferative glomerulonephritis (MPGN types I, III) is an uncommon cause of nephrotic syndrome (NS) in adults, is often associated with immune complex deposits and characterized by mesangial proliferation and reduplication of glomerular basement membranes. Majority of MPGN cases are secondary to autoimmune diseases, cryoglobulins, Hepatitis C infection, and dysproteinemias. Other causes of MPGN are less well studied and many are categorized as idiopathic.
Design: Pathology database was searched (2000-09) for renal biopsies with a diagnosis of MPGN in adults. Patients with clinical or serological evidence of systemic lupus erythematosus (ANA), cryoglobulinemia, Heptitis C/B infection, dysproteinemia (SPEP, UPEP) or lymphoproliferative disorders were excluded. Clinical data including presentation, laboratory investigations and follow up were obtained and all biopsies were reviewed for histological parameters. In addition to routine immunofluorescence staining (including K, L light chains), IgG subtyping was studied (IgG1-4).
Results: A total of 30 patients met our inclusion criteria and the mean age at presentation was 57 years (range 20-85). Two thirds of the patients presented with full NS while most others had non-nephrotic proteinuria. Renal insufficiency was common and one patient presented with acute renal failure. The amount of 24 hour proteinuria had a significant correlation with poor renal function (serum creatinine) (R=0.65, P= 0.001) while crescents, % glomerulosclerosis and interstitial fibrosis did not correlate with renal function. Except in one, immune deposits were evident in all patients either by immunofluorescence or ultrastructural examination. C3 deposits were common followed by IgG and IgM. K/L light chain restriction was detected in 12 patients (9K; 3L) and IgG subclass was monoclonal in nine patients (IgG3: 8; IgG2:1) and oligoglonal in 4 others. The possible etiological factors based on clinical history and follow up include cirrhosis, portocaval shunts, autoimmune hemolytic anemia, drugs and familial forms.
Conclusions: MPGN secondary to less characterized etiologies includes a broad spectrum and the cause may often be elusive. The light chain and IgG subtype restriction may be observed despite lack of monoclonal gammopathy and may result from chronic antigenic/immune stimulation. Histologic parameters were not strongly correlated with renal function.
Category: Kidney (does not include tumors)
Wednesday, March 2, 2011 1:00 PM
Poster Session VI # 244, Wednesday Afternoon