Membranous Glomerulonephritis Associated with Follicular B-Cell Lymphoma and Subepithelial Deposition of IgG1-κ Paraprotein

A case is described of B-cell lymphoma/chronic lymphocytic leukaemia associated with membranous glomerulonephritis in which the subepithelial deposits of immunoglobulin showed ĸ light chain restriction by immunofluorescence. Surface IgG-ĸ immunoglobulin was demonstrated on the malignant B cells, and a monoclonal protein of the same type was eluted from kidney. The mechanism of membranous glomerulonephritis in this type of lymphoid malignancy is clearly different from that in epithelial malignancies.