What an endoscopist should know about immunoglobulin-G4-associated disease of the pancreas and biliary tree.

Autoimmune pancreatitis (AIP) and IgG4-associated cholangitis (IAC) are the recently recognized pancreatobiliary manifestations of IgG4-associated systemic disease (ISD). Clinically, ISD of the pancreas and/or biliary tree may mimic pancreatic cancer, sclerosing cholangitis, or cholangiocarcinoma. Patients often present with abdominal pain, weight loss, jaundice, itch, and biochemical signs of pancreatitis and cholestasis. Tomography may reveal enlargement of the pancreas or may mimic malignant pancreatic lesions, and cholangiopancreatography may disclose irregularities of the pancreatic duct and stenoses of the distal and/or proximal common bile duct and intrahepatic bile ductules. Serum immunoglobulin G4 (IgG4) is elevated in most patients but, unlike tissue IgG4-loaded plasma cell infiltrates, is not diagnostic of the disease. The application of consensus diagnostic criteria for laboratory investigations, imaging, and histologic findings can identify patients who qualify for corticosteroid treatment. The excellent response to immunosuppressive therapy suggests an immune-mediated etiology of the disease, but the exact pathophysiological mechanisms are still under investigation. Relapse may occur after tapering down of corticosteroids, which supports the rationale of maintenance immunosuppression after remission has been induced.