[IgG4-associated cholangitis - clinical presentation of an overlooked disease entity].

IgG4-associated cholangitis (IAC) is the hepatobiliary manifestation of immunoglobulin G4-related disease, which is an immune-mediated fibroinflammatory systemic disorder characterised by often elevated IgG4 serum levels and typical histopathological findings in affected tissues. IAC is frequently (>90%) accompanied by autoimmune pancreatitis type 1 (AIP), which is the pancreatic manifestation of immunoglobulin G4-related disease. In 80-85% of the cases patients with IAC are male, above 50 years of age and present with jaundice and weight loss. A remarkable percentage of patients with IAC has a history of long-term exposure to solvents, oil products and other organic agents representing so-called "blue-collar workers". Clinical features and imaging (i. e. strictures or mass-forming lesions in the biliary tract) may mimic other biliary diseases, such as primary or secondary sclerosing cholangitis and cholangiocarinoma. The HISORt criteria are used for diagnosing IAC and comprise histologic and imaging findings, serum IgG4, organ manifestation pattern and response to immunosuppressive therapy. Serum IgG4 levels are of diagnostic value when it is above 4 times the upper limit of normal. Determination of the blood IgG4/IgG mRNA ratio using quantitative polymerase chain reaction (qPCR) is an accurate diagnostic tool currently under clinical validation. The majority of patients show an excellent response to corticosteroid therapy. Symptom recurrence, however, is common making long-term treatment with low-dose prednisolone and/or azathioprine frequently necessary.