title: The use of immunoglobulin g4 immunostaining in diagnosing pancreatic and extrapancreatic involvement in autoimmune pancreatitis.
abstract: OBJECTIVE
  Autoimmune pancreatitis (AIP) is recognized increasingly as a multisystem disorder. We evaluated the use of immunoglobulin (Ig)G4 immunostaining of pancreatic and extrapancreatic biopsy specimens to make a definitive diagnosis of AIP.
  
  
  METHODS
  Seventeen biopsy specimens and 3 gallbladder resections were assessed from 11 patients with clinical and radiologic features of AIP. Biopsy specimens from pancreas, liver, colon, stomach, duodenum, bone marrow, salivary gland, and kidney were analyzed morphologically, immunostained for IgG4-positive plasma cells, and compared with controls.
  
  
  RESULTS
  Positive IgG4 immunostaining enabled a definitive diagnosis in 10 of 11 (91%) AIP patients. In both pancreatic and extrapancreatic tissues, high levels of IgG4 immunostaining (>10 IgG4-positive plasma cells/high-power field) were found in 17 of 20 (85%) specimens from AIP patients compared with 1 of 175 (0.6%) specimens from controls (P < .05). Positive extrapancreatic IgG4 immunostaining was found in 8 of 11 (73%) patients, including all those with diagnostic features in the pancreas. Increased tissue IgG4 was found irrespective of serum IgG4 level.
  
  
  CONCLUSIONS
  The finding of IgG4 immunostaining within a range of clinically involved tissues supports the hypothesis that AIP is a multisystem disease. Positive IgG4 immunostaining in extrapancreatic tissues may allow a definitive diagnosis of AIP to be made in those with evidence of pancreatic disease, without the necessity of pancreatic biopsy or surgical exploration. Immunostaining of involved tissue for IgG4 may be particularly useful when AIP is suspected clinically but the serum IgG4 level is normal.
authors: Department of Histopathology, University College Hospital, London, United Kingdom.
authors: Maesha G
authors: MG
authors: Deheragoda
authors: Nicholas I
authors: NI
authors: Church
authors: Manuel
authors: M
authors: Rodriguez-Justo
authors: Philippa
authors: P
authors: Munson
authors: Neomal
authors: N
authors: Sandanayake
authors: Edward W
authors: EW
authors: Seward
authors: Keith
authors: K
authors: Miller
authors: Marco
authors: M
authors: Novelli
authors: Adrian R W
authors: AR
authors: Hatfield
authors: Stephen P
authors: SP
authors: Pereira
authors: George J M
authors: GJ
authors: Webster
mesh_terms: D000328:Adult; D000368:Aged; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology / Q000378:metabolism*; D001327:Autoimmune Diseases / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology; D003106:Colon / Q000473:pathology; D003937:Diagnosis, Differential; D004386:Duodenum / Q000473:pathology; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism*; D007668:Kidney / Q000473:pathology; D008099:Liver / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000473:pathology; D010195:Pancreatitis / Q000175:diagnosis* / Q000276:immunology / Q000378:metabolism; D011379:Prognosis; D012469:Salivary Glands / Q000473:pathology; D013270:Stomach / Q000473:pathology
chemical_list: D000888:Antibodies, Anti-Idiotypic; D015415:Biomarkers; D007074:Immunoglobulin G