Anti-phospholipase A2 receptor in Non-lupus Patients with Membranous Nephropathy and Crescents

Abstract

Introduction: Anti-phospholipase A2 receptor (PLA2R) is detected in approximately 70% of biopsies of “primary” membranous nephropathy (MN). Crescents in MN in non-lupus patients suggest additional injury, such as antineutrophil cytoplasmic antibody (ANCA) or anti-glomerular basement membrane (anti-GBM)-associated glomerulonephritis and is postulated to reflect injury by a mechanism that unmasks cryptic epitopes leading to the second autoantibody. Methods: We studied PLA2R staining in non-lupus patients with MN and crescents. Native renal biopsies in 16 non-lupus patients with MN and crescents were stained for PLA2R. Results: The patients included 5 women and 11 men, with mean age 61 yrs and elevated serum creatinine (mean 4.68 mg/dL). Hematuria and proteinuria (mean 4.97 g/d) were documented in 13 patients. Two patients had positive serum anti-GBM antibody. Nine of eleven patients tested for ANCA were positive, with p-ANCA (n=4), c-ANCA (n=2), or both (n=1), with two not specified. On average, 27% of glomeruli had crescents. One patient had an initial biopsy with MN, 4 years later had MN with crescent, and 7 years later had rebiopsy with persistent MN with crescents. One patient had ANCA-associated vasculitis, and 5 years later had MN and crescent. The remaining 14 patients had concurrent diagnoses of MN and crescents. PLA2R was positive in 5 cases, 3 with ANCA positivity, 2 with unknown ANCA status, and none with anti-GBM disease. The patient with initial MN preceding crescent was PLA2R positive; the patient with initial ANCA-associated vasculitis preceding MN was PLA2R negative. Conclusions: Most patients (64%) presented with concomitant MN and crescents, with rare occurrence of an initial disease process followed later by the second injury. PLA2R was positive in 31% of patients, suggesting most are secondary MN. Further study to determine the cryptic epitopes may shed light on the triggering mechanisms for these rare but unlikely coincidental glomerular injuries.