Autoimmune pancreatitis and IgG4-related systemic diseases.

Autoimmune pancreatitis (AIP) is a rare form of chronic pancreatitis that is characterized by lymphoplasmacytic infiltrate, storiform fibrosis, obliterative phlebitis, and increased IgG4(+) plasma cells. Serum IgG4 levels usually are elevated. Patients with AIP frequently have disease affecting other organs or sites; these tissues show similar histologic changes, including increased IgG4(+) plasma cell infiltrate and response to corticosteroid...