Zuo Y, Cavalcante L.B, Smelser J.M, Sanghani N, Dwyer J.P, Lewis J.B, Fogo A.B: Anti-Phospholipase A2 Receptor in Nonlupus Patients with Membranous Nephropathy and Crescents. Glomerular Diseases DOI 10.1159/000520641
Primary membranous nephropathy (pMN) (that form not associated with systemic disease, like SLE) can occasionally present with or develop super-imposed crescentic glomerulonephritis (GN), along with rapidly progressive deterioration of kidney function. The pathogenesis underlying this uncommon event can often be linked to the appearance of ANCA-associated vasculitis (AAV) or anti-GBM (aGBM) disease, but the role of anti-PLA2R antibodies in this subset of pMN is largely unknown.
Zuo and co-workers retrospectively analyzed a cohort of 16 cases of pMN (5 females and 11 males) who had developed crescentic GN, with particular attention to their PLA2R status, using PLA2R staining of biopsy material, compared to ANCA and anti-GBM antibody pathogenesis.
The mean age was 61 years, average proteinuria at presentation 4.97 g/day, and initial serum creatinine was 4.68 mg/dL. Two patients (13%) had anti-GBM disease; 9 (of 11 tested) (56%) had ANCA; and 5 had neither ANCA nor anti-GBM or were unknown. Five of the 16 patients were PLA2R antigen positive (none of the anti-GBM cases were positive for PLA2R antigen). The crescentic disease and pMN were discovered concurrently in 14 cases, and crescentic disease followed pMN in 2 cases. Overall, 78% of the patients with concurrent pMN and crescentic GN were either ANCA or anti-GBM positive and 69% were PLA2R antigen negative.
A retrospective study of such a small cohort cannot uncover the discrete pathogenic links between PLA2R and crescentic glomerular disease in pMN. But the findings indicate that complicating crescentic disease in pMN (regardless of PLA2R status) is commonly due to well-defined auto-immune processes. Whether this is due to a common underlying genetically determined predisposition (for example due to HLA specificities on chromosome 6) or due to release of auto-antigenic epitopes from damaged podocytes or GBM, or both, remains uncertain.