Chapter 27. Autoimmune Pancreatitis

• Presentation with obstructive jaundice.
• Diffuse swelling and enlargement of the pancreas, especially the head, the latter mimicking carcinoma of the pancreas.
• Diffuse irregular narrowing of the pancreatic duct on ERCP or MRCP.
• Elevated serum IgG4 level.
• Extrapancreatic and intrahepatic bile duct strictures.
• Resolution or marked improvement in pancreatic and extrapancreatic manifestations after corticosteroid treatment.
• Pancreatic biopsies reveal extensive fibrosis and lymphoplasmacytic infiltration.
• HISORT criteria used to establish the diagnosis.

Autoimmune pancreatitis is a rare disorder of presumed autoimmune causation with characteristic chemical, histologic, and morphologic findings. It is referred to by various names, including nonalcoholic destructive pancreatitis, tumefactive pancreatitis, and sclerosing pancreatitis, depending in part on specific pathologic findings and on the presence of extrapancreatic manifestations. However, it is believed that the pathologic heterogeneity may reflect different stages or manifestations of the same disease.

Autoimmune pancreatitis has been described as a primary pancreatic disorder and is also associated with other disorders of presumed autoimmune etiology, including primary sclerosing cholangitis, primary biliary sclerosis, retroperitoneal fibrosis, rheumatoid arthritis, and Sjögren syndrome. As a result, it has been proposed that autoimmune pancreatitis represents a systemic autoimmune disease.

Symptoms and Signs

Mild symptoms, usually abdominal pain, are present but attacks of acute pancreatitis are unusual. Furthermore, autoimmune pancreatitis is not a common cause of idiopathic recurrent pancreatitis. In the United States, 50–65% of patients with autoimmune pancreatitis present with obstructive jaundice. Weight loss and new onset of diabetes may also occur. Patients who have associated autoimmune conditions have corresponding clinical features. In this regard, Sjögren syndrome, rheumatoid arthritis, retroperitoneal fibrosis, ulcerative colitis, autoimmune thyroiditis, tubulointerstitial nephritis, and mediastinal adenopathy have all been reported in patients with autoimmune pancreatitis (Tables 27–1 and 27–2).