Membranous nephropathy as a rare renal manifestation of IgG4-related disease.

IgG4-related disease, a newly described immune-mediated disorder with tissue infiltration of IgG4-positive plasma cells, has been reported in nearly every organ. In the kidney, it manifests as IgG4-related tubulointerstitial nephritis (TIN) but may also present as membranous nephropathy. We report a patient with IgG4 renal disease who had membranous nephropathy as well as TIN.