Phospholipase A2 Receptor Staining Is Not a Sensitive Indicator of Idiopathic Membranous Glomerulopathy in Children
Larry Nicholas Cossey, Patrick D Walker, Christopher P Larsen. Nephropath, Little Rock, AR; University of Arkansas for Medical Sciences, Little Rock, AR
Background: Anti-phospholipase A2 receptor (PLA2R) autoantibodies have recently been implicated as a causative agent in most cases of adult idiopathic membranous glomerulopathy (MG). PLA2R staining of renal biopsies in two recent large case series of adults with idiopathic MG showed a sensitivity of 74%/75% for the detection of idiopathic MG. To our knowledge, this is the first case series on PLA2R staining in a pediatric population with MG.
Design: The database at our institution was searched from 2005-2012 for patients age 17 and under with MG and negative ANA serology. Forty-one consecutive cases were identified and clinical follow-up was performed to confirm idiopathic MG (negative testing for autoimmune disease, HBV, HCV, sarcoidosis, and syphilis). Twenty-two patients were included in the study.
Results: Patients showed a 1:1 male to female ratio with average age of 14 years (range 4-17 years). 82% of patients reported proteinuria (avg. 6.8 gm/day) with average creatinine of 0.72 mg/dl (range 0.2-1.3 mg/dl). IgG staining (granular, capillary wall) was present in 100% of patients at 2+ or greater intensity and C3 staining was present in 77%. PLA2R staining was identified in 10 patients providing a sensitivity of 45% (CI 25-67%) for the detection of idiopathic MG. Bovine serum albumin staining was performed in all PLA2R negative cases and showed no positivity. IgG subtypes were performed on five of the PLA2R negative cases with 3/5 showing IgG4 co-dominance and none showing IgG4 restriction. By electron microscopy all cases showed subepithelial deposits with mesangial and subendothelial deposits being present in 50% and 5%, respectively. Staging (Ehrenreich and Churg) showed 41% of patients at stage I, 18% at stage II, and 41% at stage III, with 70% of PLA2R+ patients being stage III.
Conclusions: PLA2R staining within a population of pediatric MG showed a sensitivity of 45% for idiopathic MG which is much lower than previously reported in adult populations. Also, within the PLA2R negative cases no restriction to IgG4 subclass was identified. These PLA2R-negative cases either represent a population of misclassified secondary membranous glomerulopathy in which the secondary etiology is undetectable at the time of renal presentation or an as yet undefined etiology of primary membranous glomerulopathy caused by non-PLA2R antibodies. This series suggests that PLA2R staining lacks sensitivity for the detection of idiopathic MG in children.
Category: Kidney (does not include tumors)
Monday, March 4, 2013 1:00 PM
Poster Session II # 228, Monday Afternoon