title: Serum IgG4-negative autoimmune pancreatitis.
abstract: BACKGROUND
  Autoimmune pancreatitis (AIP) is considered to be a pancreatic lesion of IgG4-related systemic disease, but about 20% of AIP patients do not have elevated serum IgG4 levels. This study aimed to clarify the pathophysiology of AIP patients without elevated serum IgG4 levels.
  
  
  METHODS
  Fifty-eight AIP patients were divided into 2 groups: those with elevated serum IgG4 levels (>135 mg/dl; SIgG4-positive AIP) and those without (SIgG4-negative AIP). The 2 groups' clinical, serological, radiological, and histological findings, as well as salivary and lacrimal gland function, were compared.
  
  
  RESULTS
  Serum IgG4 levels were elevated in 45 AIP patients and normal in 13 patients. In SIgG4-negative AIP patients, the female ratio tended to be high; obstructive jaundice was less likely; abdominal pain and acute pancreatitis were more likely; segmental swelling of the pancreatic body and/or tail was more common; sclerosing extrapancreatic lesions, salivary and lacrimal gland dysfunction, and abundant infiltration of IgG4-positive plasma cells in the gastric mucosa were less likely; and conservative follow-up was sometimes implemented. Histological examination of the pancreas of SIgG4-negative AIP showed lymphoplasmacytic sclerosing pancreatitis (LPSP) rather confined to the pancreas (n = 4), inadequate material (n = 2), and pancreatic fibrosis showing infiltration of lymphocytes without infiltration of IgG4-positive cells or neutrophils (n = 2).
  
  
  CONCLUSIONS
  Clinicopathological features of SIgG4-negative AIP differed from those of SIgG4-positive AIP. Some SIgG4-negative AIP cases are LPSP rather confined to the pancreas. SIgG4-negative AIP may include idiopathic duct-centric pancreatitis (IDCP) or sclerosing pancreatitis other than LPSP or IDCP, but further studies are needed to clarify this issue.
authors.affiliation: Department of Internal Medicine, Tokyo Metropolitan Komagome Hospital, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo, 113-8677, Japan. kamisawa@cick.jp
authors.forename: Terumi
authors.initials: T
authors.lastname: Kamisawa
authors.forename: Kensuke
authors.initials: K
authors.lastname: Takuma
authors.forename: Taku
authors.initials: T
authors.lastname: Tabata
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Inaba
authors.forename: Naoto
authors.initials: N
authors.lastname: Egawa
authors.forename: Koji
authors.initials: K
authors.lastname: Tsuruta
authors.forename: Tsunekazu
authors.initials: T
authors.lastname: Hishima
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Sasaki
authors.forename: Takao
authors.initials: T
authors.lastname: Itoi
mesh_terms: D000368:Aged; D001327:Autoimmune Diseases / Q000175:diagnosis / Q000276:immunology / Q000503:physiopathology*; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D010195:Pancreatitis / Q000175:diagnosis / Q000276:immunology / Q000503:physiopathology*; D012189:Retrospective Studies; D012698:Serologic Tests
chemical_list: D015415:Biomarkers; D007074:Immunoglobulin G
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