Serologic issues in IgG4-related systemic disease and autoimmune pancreatitis.
OBJECTIVE
IgG4-related systemic disease (ISD) is a recently recognized syndrome affecting multiple organs. Autoimmune pancreatitis (AIP) is the pancreatic manifestation of ISD and mimics pancreatic cancer. Current data show frequent association with serum IgG4 elevation and other serologic abnormalities. Here we explore the diagnostic and possible prognostic utility and pathogenetic implications of serologic abnormalities in ISD.


RESULTS
Serum IgG4 elevations (>140 mg/dl) are seen in 70-80% of AIP patients and also in 5% of normal population and 10% of pancreatic cancer making it an unsuitable single marker for diagnosis. However, when combined with other features of AIP, it can be of great diagnostic value though its utility in monitoring of therapy or as a marker or predictor of relapse is limited. Several other antibodies have been identified in AIP against pancreas-specific antigens like trypsinogens I and II, pancreatic secretory trypsin inhibitor (PSTI) and plasminogen binding protein (PBP) and other nonpancreas-specific antigens. Anti-PBP antibodies appear to have potential diagnostic utility but require further validation.


CONCLUSIONS
No single serologic marker is diagnostic of ISD. Serum IgG4 elevation has convincing diagnostic utility when combined with other disease features although its value in disease monitoring may be limited.
Fiterman Center for Digestive Diseases, Mayo Clinic, Rochester, MN 55905, USA.
Raghuwansh P
RP
Sah
Suresh T
ST
Chari
D000918:Antibody Specificity; D001323:Autoantibodies / Q000097:blood; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000175:diagnosis / Q000276:immunology*; D015415:Biomarkers / Q000097:blood; D002352:Carrier Proteins / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood*; D010179:Pancreas / Q000276:immunology; D010195:Pancreatitis / Q000175:diagnosis / Q000276:immunology*; D010958:Plasminogen / Q000378:metabolism; D014362:Trypsinogen / Q000276:immunology
D001323:Autoantibodies; D001324:Autoantigens; D015415:Biomarkers; D002352:Carrier Proteins; D007074:Immunoglobulin G; D010958:Plasminogen; D014362:Trypsinogen