title: Diagnosis of autoimmune pancreatitis: the Mayo Clinic experience.
abstract: OBJECTIVE
  The Japan Pancreas Society criteria for diagnosis of autoimmune pancreatitis (AIP) mandate presence of characteristic imaging (diffuse pancreatic enlargement with diffusely irregular, narrow pancreatic duct). AIP has unique histologic features associated with infiltration of tissues of affected organs with abundant IgG4-positive cells. We propose expanded diagnostic criteria for AIP with a cohort of histologically confirmed AIP.
  
  
  METHODS
  We reviewed the pancreatic imaging findings on computed tomography scans, serum IgG4 levels, other organ involvement, and response to steroids in 29 consecutive patients who met histologic criteria for AIP.
  
  
  RESULTS
  Computed tomography scans (n = 22) showed diffuse pancreatic enlargement in 6 (27%) patients; the rest had focal enlargement, distinct mass, normal pancreas, or focal acute pancreatitis. Serum IgG4 level was elevated in 15 of 21 (71%) patients, and other organ involvement (eg, intrahepatic biliary strictures) was noted in 11 of 29 (38%) patients. All 17 patients treated with steroids exhibited resolution/marked improvement of pancreatic/extrapancreatic manifestation. On the basis of this experience we propose that diagnosis of AIP can be made in patients with > or =1 of these criteria: (1) diagnostic histology, (2) characteristic imaging on computed tomography and pancreatography with elevated serum IgG4 level, or (3) response to steroid therapy of pancreatic/extrapancreatic manifestations of AIP. Twenty additional patients met expanded diagnostic criteria for AIP, and their demographic and clinical profile was similar to that of the 29 patients meeting histologic criteria.
  
  
  CONCLUSIONS
  AIP defined by histological criteria shows a wide spectrum of radiologic features, with characteristic imaging seen only in a minority. Incorporation of additional features into current diagnostic criteria can identify the full spectrum of clinical presentations of AIP.
authors.affiliation: Division of Gastroenterology and Hepatology, Mayo Clinic College of Medicine, Rochester, Minnesota 55905, USA. suresh@mayo.edu
authors.forename: Suresh T
authors.initials: ST
authors.lastname: Chari
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Smyrk
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Levy
authors.forename: Mark D
authors.initials: MD
authors.lastname: Topazian
authors.forename: Naoki
authors.initials: N
authors.lastname: Takahashi
authors.forename: Lizhi
authors.initials: L
authors.lastname: Zhang
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Clain
authors.forename: Randall K
authors.initials: RK
authors.lastname: Pearson
authors.forename: Bret T
authors.initials: BT
authors.lastname: Petersen
authors.forename: Santhi Swaroop
authors.initials: SS
authors.lastname: Vege
authors.forename: Michael B
authors.initials: MB
authors.lastname: Farnell
mesh_terms: D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001327:Autoimmune Diseases / Q000175:diagnosis* / Q000188:drug therapy; D019992:Databases as Topic; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D010179:Pancreas / Q000473:pathology; D010195:Pancreatitis / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D000305:Adrenal Cortex Hormones; D007074:Immunoglobulin G