Diagnosing Autoimmune Pancreatitis

Posted by Elaine Moore Dec 15, 2007

Autoimmune pancreatitis is an autoimmune disease that occurs alone or in patients with Sjogren’s syndrome and primary sclerosing cholangitis. Autoimmune pancreatitis causes an enlarged pancreas with narrowing of the pancreatic duct and is characterized by abdominal pain, jaundice and weight loss. Although immune mediated, autoimmune pancreatitis can be difficult to differentiate from other forms of pancreatitis as well as pancreatic ductal adenocarcinoma.

Elevated IgG4 Levels

Patients with autoimmune pancreatitis have previously been found to have increased levels of the immunoglobulin G4 (IgG4). In a recent article published in Modern Pathology, researchers describe finding moderate to marked numbers of IgG4 in plasma cells in biopsy specimens taken from patients with autoimmune pancreatitis.

Subtypes of Autoimmune Pancreatitis

Autoimmune pancreatitis includes:

• Disorders of lymphoplasmacytic sclerosing pancreatitis
• Idiopathic duct-destructive pancreatitis

Value of IgG4 in Biopsy Specimens

In tissue studies, 16/17 of patients with lymphoplasmacytic sclerosing pancreatitis showed evidence of IgG4 positive plasma cells whereas IgG4 positive plasma cells were seen in 5/12 patients with idiopathic duct-destructive pancreatitis. The IgG4 positive cells were distributed in and around ducts, in interlobular fibrous tissue and in peripancreatic fat (adipose tissue surrounding the pancreas).

Among patients with ductal adenocarcinoma, 22/25 patients showed no IgG4 in pancreatic biopsy specimens, and 8 of 9 patients with alcoholic pancreatitis showed no signs of IgG4 cells.

Therefore, tests for IgG4 in tissue studies can be used to help differentiate autoimmune from non-autoimmune conditions of pancreatitis such as chronic alcoholic pancreatitis. Furthermore, IgG4 tests can be used to help distinguish lymphoplasmacytic sclerosing pancreatitis from idiopathic duct-destructive pancreatitis.

Importance of Correct Diagnosis

Autoimmune pancreatitis usually responds well to corticosteroid treatment. Alcoholic pancreatitis and pancreatic adenocarcinoma do not respond to corticosteroids.

Resource:

Lizhi Zhang, Kenji Notohara, Michael Levy, Suresh Chari, and Thomas Smyrk, IgG4-positive plasma cell infiltration in the diagnosis of autoimmune pancreatitis, Modern Pathology, September 2006, 20, 23-28.