Membranous-Like Glomerulopathy with Masked IgG-Kappa Deposits

Immunoglobulin deposits identified on renal biopsy samples by paraffin immunofluorescence that show negative staining by routine immunofluorescence on frozen tissue have become known as “masked” deposits. Membranous-like glomerulopathy with masked IgG kappa (κ) deposits is a recently recognized pattern of immune complex deposition characterized by masked deposits that show IgG κ restriction and are subepithelial and mesangial by electron microscopy. The subepithelial deposits can be appreciated (arrow) in the Jones methenamine silver stain shown here. The patients are most commonly young females <40 years of age with positive autoimmune serologic study results such as ANA, although a few carry a diagnosis of well-defined autoimmune disease such as lupus. The outcome is variable, as some patients show spontaneous remission and mild disease whereas others progressed to ESRD.