IgG4-related kidney disease: Pathological features: Membranous glomerulonephritis

IgG4-related membranous glomerulonephritis (IgG4-MGN) is the most commonly occurring glomerular disease in IgG4-related disease (IgG4-RD). Patients present with proteinuria, usually nephrotic-range, with or without renal insufficiency. The male predominance and occurrence in middle-aged to older adults parallels other recognized organ manifestations of IgG4-RD. IgG4-MGN shows histologic and immunophenotypic similarity to primary membranous glomerulonephritis, with the notable exception of negative staining for antibodies to the phospholipase A2 receptor (PLA2R). By definition, immune complex deposits containing IgG, kappa, and lambda and C3 are present along the subepithelial aspect of the glomerular basement membranes. In one series of IgG4-MGN, approximately half of the cases did not show concurrent IgG4-related tubulointerstitial nephritis (IgG4-TIN), although patients had other organ involvement by IgG4-RD. IgG4-MGN represents a pattern of tissue involvement that is distinct from most other manifestations of IgG4-RD. Although most organs affected by IgG4-RD demonstrate an “inflammatory” histologic picture, IgG4-MGN is characterized by immune complex deposits in the absence of corresponding inflammation.