Membranous glomerulopathy: emphasis on secondary forms and disease variants

Membranous glomerulopathy (MGN) is characterized by subepithelial immune complex deposits and glomerular basement membrane (GBM) thickening. The majority of patients present with nephrotic syndrome and outcomes are variable. Pathologically, deposits at sites other than the subepithelial aspect of the GBM favor the presence of secondary forms of MGN which are seen most commonly in the setting of autoimmune disease, infection, neoplasia, and with certain therapeutic agents. MGN is the most common form of de novo glomerular disease seen in the renal allograft and may be seen concurrently with other forms of glomerular disease including focal segmental glomerulosclerosis, IgA nephropathy, diabetic nephropathy, and anti-TBM nephritis. This review emphasizes the detection of secondary forms and variants of MGN.