TYPE-1 Autoimmune Pancreatitis
What is type-1 autoimmune pancreatitis in the framework of an IgG4-related disease?
Lymphoplasmacytic sclerosing pancreatitis as part of a systemic fibroinflammatory disease that may affect several organs (liver, kidneys, lungs, etc.).
How is it diagnosed?
Type-1 autoimmune pancreatitis manifests itself mainly in men (80% of cases) ages 50 and over. Revealing symptoms may include obstructive jaundice secondary to a cephalic pancreatic mass or the presence of cholangitis (intrapancreatic or diffuse cholangitis of the biliary tree). Other symptoms may include clear alteration of general health, with diabetic decompensation, anorexia and weight loss, thus mimicking pancreatic adenocarcinoma. As an IgG4-type disease, complications involving other organs (whether synchronous or metachronous) are present in more than 50% of cases. The patient may thus show symptoms of these extrapancreatic complications.
Imaging is used to establish the autoimmune origin (heterogeneity of the pancreatic parenchyma, peripancreatic halo, loss of pancreatic lobulations with “sausage” appearance, irregular diameter of the main pancreatic duct, tumour-like appearance). Other organs may be affected (cholangitis, retroperitoneal fibrosis, etc.).
The serum IgG4 level is high (> 1.35 g/L or more than twice the normal level) in most cases.
A pancreatic biopsy, if performed, will reveal a lymphoplasmacytic infiltrate and the presence of plasmacytes strongly expressing the anti-IgG4 antibody.
What is its specific treatment?
In case of symptoms, treatment is based on corticosteroids (40 mg/day) for one month, followed by progressive decrease in dosage. In case of resistance to or dependence on corticosteroids, treatment with immunomodulators should be discussed in a specialised centre.