Abstract
Objectives: To assess the prognostic value of IgG4 reactivity in biopsy-proven cases of idiopathic membranous nephropathy (iMN) and to outline its potential in guiding therapy. Methods: A retrospective study of biopsy-proven iMN cases from January 1997 to August 2013 was undertaken. Patients were identified, and an extensive analysis of the clinical and histological parameters were performed. The primary endpoint was a worse renal outcome, which was defined as doubling of the serum creatinine baseline value. Results: The study included 52 patients, with mean age of 38.0 years. The median baseline creatinine was 112.7 ± 36.3 umol/l among those with positive staining for IgG4 and 67.4 ± 19.3 umol/l among those with negative staining for IgG4 (P=0.5). There was no significant difference in the 24 hr urine protein between IgG4 positive and IgG4 negative staining cases (P=0.375). The probability of doubling serum creatinine was similar among those with or without IgG4 deposition. Follow up of the patients revealed that 23.4% of those with positive IgG4 and 14% of those with negative IgG4 had deterioration of the renal function. The prevalence and severity of tubulo-interstitial inflammation was not statistically different between the two groups. Conclusion: There was no relationship between IgG4 positivity and the severity of clinical and/or histological parameters in patients with iMN. IgG4 reactivity had no impact on the long-term outcome of the patients. Further studies are needed to outline the potential use of targeted therapy against IgG4 auto-antibody in a certain category of patients with membranous nephropathy.
Highlights
Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome in adults worldwide, and 75% of cases are idiopathic [1]
Subsequent reports on the development of idiopathic membranous nephropathy (iMN) showed that apart from phospholipase A2 receptor 1 (PLA2R1), there is the involvement of human leukocyte antigen DQA1 allele that makes one susceptible to autoimmunity [12], and the production of IgG4 anti-PLA2R1, that binds to the epitopes on the surface of the podocytes to form immune complexes [10]
In contrast to previous reports [5,6,7,8,9], our study showed no relationship between the presence of IgG4 deposition and the severity of iMN
Summary
Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome in adults worldwide, and 75% of cases are idiopathic [1]. It is an autoimmune disease characterized by thickening of the glomerular capillary basement membrane due to inflammation [1,2]. A defect at the podocyte level hinders proper filtration and undermines kidney function by the formation of immune complexes [2,3]. The deposition of immune complexes leads to potential end-stage renal disease (ESRD). Histological findings include alterations in basement membrane structure and IgG containing subepithelial electron-dense deposits with a classical presentation of marked proteinuria and nephrotic syndrome [4]
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