title: Pseudotumors due to IgG4 immune-complex tubulointerstitial nephritis associated with autoimmune pancreatocentric disease.
abstract: Autoimmune pancreatitis (AIP) is a mass-forming chronic fibroinflammatory condition centered on the pancreatobiliary system and characterized by predominant immunoglobulin G4 (IgG4)-positive plasma cells. Recent reports have brought to light the multiorgan involvement of this disease. We describe a series of 5 cases of tubulointerstitial nephritis (TIN) associated with AIP and characterize the clinical, pathologic, ultrastructural, and immunopathologic features of TIN. The specimens consisted of 4 biopsies and 1 nephrectomy. The average patient age was 64 years (range 45 to 78) and the male to female ratio was 4:1. All had histologic and/or clinical and radiographic evidence of AIP, mass-forming sclerosing cholangitis, or both. The clinical impression in 4 patients was a renal mass or vasculitis. Two patients had renal insufficiency. Histologic preparations revealed a dense tubulointerstitial lymphoplasmacytic infiltrate. Eosinophils were often numerous. Tubulitis and tubular injury were present, along with tubular atrophy with focally thickened tubular basement membranes (TBMs). The histologic appearance ranged from a cellular, inflammatory pattern without tubular atrophy to a striking expansive interstitial fibrosis with tubular destruction. The nephrectomy specimen demonstrated a masslike nodular pattern of inflammation with normal renal tissue elsewhere. Glomeruli were uninvolved. By immunohistochemistry or immunofluorescence, numerous plasma cells in the infiltrate were positive for IgG4. TBM granular IgG deposits, predominantly of the IgG4 subclass, were detected in 4 of 5 cases by either immunofluorescence or immunohistochemistry. By electron microscopy, corresponding amorphous electron-dense deposits were present in the TBM in these cases. This type of TIN, typically characterized by a masslike lesion consisting of a lymphoplasmacytic infiltrate with eosinophils and prominent IgG4-positive plasma cells and immune-complex deposits in the TBM, may be part of a systemic IgG4-related disease, which we term "IgG4-associated immune complex Multiorgan Autoimmune Disease" (IMAD).
authors: Departments of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114, USA. cornell@alum.mit.edu
authors: Lynn D
authors: LD
authors: Cornell
authors: Sonia L
authors: SL
authors: Chicano
authors: Vikram
authors: V
authors: Deshpande
authors: A Bernard
authors: AB
authors: Collins
authors: Martin K
authors: MK
authors: Selig
authors: Gregory Y
authors: GY
authors: Lauwers
authors: Laura
authors: L
authors: Barisoni
authors: Robert B
authors: RB
authors: Colvin
mesh_terms: D000368:Aged; D000936:Antigen-Antibody Complex / Q000276:immunology; D001327:Autoimmune Diseases / Q000150:complications / Q000276:immunology / Q000473:pathology*; D001485:Basement Membrane / Q000648:ultrastructure; D005260:Female; D006104:Granuloma, Plasma Cell / Q000150:complications / Q000276:immunology / Q000473:pathology*; D006801:Humans; D007124:Immunoenzyme Techniques; D007074:Immunoglobulin G / Q000032:analysis*; D007684:Kidney Tubules / Q000276:immunology / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000150:complications / Q000276:immunology / Q000473:pathology*; D010195:Pancreatitis / Q000150:complications / Q000276:immunology / Q000473:pathology*; D010950:Plasma Cells / Q000276:immunology / Q000473:pathology / Q000648:ultrastructure
chemical_list: D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G