IgG4-Related Tubulointerstitial Nephritis With Membranous Nephropathy

We describe a 67-year-old woman who presented with significant proteinuria and hematuria. Kidney biopsy showed immunoglobulin G4 (IgG4)-related tubulointerstitial nephritis (TIN) with concurrent membranous nephropathy. IgG4-related TIN is a recently described entity that presents with progressive decreased kidney function and is characterized by a plasma cell-rich infiltrate that is positive for IgG4. It is associated with patchy, often...