Autoimmune pancreatitis (AIP) is a rare form of chronic pancreatitis characterized by diffuse enlargement of the pancreas, narrowing of the pancreatic duct, and lymphoplasmacytic infiltration and fibrosis. AIP presents similarly to pancreatic cancer, so definite diagnosis is imperative to avoid unnecessary major surgery.
Type I AIP is the pancreatic manifestation of systemic IgG4-related disease. Histologically, it is a lymphoplasmacytic sclerosing pancreatitis (LPSP). Refer to ARUP Consult’s IgG4-related disease topic for more information.
Type 2 AIP, or idiopathic duct-centric pancreatitis, is IgG4 negative and is characterized by granulocytic lesions. Type 2 is more rare and less well understood.
Both types respond to steroid therapy, although type 1 AIP will often (20-60% of the time) relapse (Hart, 2015).
Last Update: October 2019