IgG4-related tubulointerstitial nephritis.

Tubulointerstitial nephritis (TIN) is a disease pattern with heterogeneous causes. Recently a specific subtype of autoimmune TIN, IgG4-related TIN, has been identified that is part of systemic IgG4-related disease/ autoimmune pancreatitis. On biopsy, this TIN shows an IgG4+ plasma cell-rich infiltrate, akin to the pancreatic tissue findings in autoimmune pancreatitis, and may show tubulointerstitial immune complex deposits. Notably, some cases may be mass-forming. Recognition of this specific type of TIN can guide appropriate patient therapy.