Serum IgG4 in autoimmune pancreatitis: A marker of disease severity and recurrence?

Abstract

Autoimmune pancreatitis (AIP) is a well-defined clinical entity athologically different from all the other forms of chronic panreatitis. Since its first description, the concept of the disease has reatly changed over time. On the basis of pathological findings, the disease has been ecently classified in type 1 AIP (also called Lympho-Plasmacytic clerosing Pancreatitis – LPSP), and type 2 AIP (also called Idiopathic uct-centric Chronic Pancreatitis – IDCP), as reported by Matsubyashi et al. [1]. These two forms of AIP seem to have different linical profiles, since type 1 AIP is characterized by other organ nvolvement (biliary tract, salivary glands, gastrointestinal tract, idney, retroperitoneum) and frequent relapses after steroid treatent, whereas type 2 AIP seems to be associated with ulcerative olitis and does not relapse. However, both forms show a good esponse to steroids. Morphologically, the disease has been classified in focal AIP, nvolving only a part of the pancreatic gland at imaging techniques, ith or without the presence of a low-density mass, mimicking ancreatic adenocarcinoma, and in diffuse AIP, involving all the lands [2]. This classification is clinically relevant, since the diagostic algorithm is different, as recently reported [3]. Indeed, in he presence of focal AIP, particularly in the presence of a lowensity mass, a diagnosis of pancreatic adenocarcinoma must be xcluded before steroid treatment, whereas in the diffuse form, the ifferential diagnosis is with acute pancreatitis and a diagnosis of holangiocarcinoma needs to be excluded only in the presence of a ingle stenosis of the common biliary tract. In 2001, Hamano et al. [4] reported for the first time high levls of serum IgG4 (sIgG4) in patients suffering from AIP, called in his paper sclerosing pancreatitis, but not in normal subjects and in atients suffering from “ordinary” chronic pancreatitis, or in other utoimmune diseases (primary biliary cirrhosis, primary sclerosng cholangitis, or Sjogren’s syndrome) or in pancreatic cancer. he authors therefore suggested the use of sIgG4 in the diagnosis f AIP, since sensitivity and specificity were very high (respecively 95% and 97%). This paper had a tremendous impact in the