Retroperitoneal fibrosis (RF) is a rare disorder that has many risk factors such as radiation, asbestos and others, but now might fall into a set of diseases called IgG4 related systemic disease. IgG4 has been associated with many organs - mainly RF, autoimmune pancreatitis and skin involvement. Renal involvement is significant as well. It is characterized by a high level of serum IgG4 and dense infiltration of IgG4-positive plasma cells into multiple organs, with the kidney being one representative target.
The main renal manifestations are:
1. Tubulo interstitial disease. 30% of patients with autoimmune pancreatitis have interstitial renal involvement. Usually have elevated serum IgG4 levels. They have tubular basement membrane deposits. See references below for details. Staining for IgG4 plasma cells might be beneficial in the kidney.
2. Glomerular disease: Usually Membranous GN, IgA Nephropathy
3. Obstructive disease( most common):- due to mass effect of RF.