Autoimmune Pancreatitis with Normal Serum IgG4 Concentrations: What Is the Correct Classification for Such Patients?
The autoimmune pancreatitis (AIP) seen in Japan occurs preferentially in older men, presents with jaundice in many cases, and is seldom associated with symptoms and signs of acute pancreatitis. Elevated serum IgG4 concentrations are noted in a high propor
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Autoimmune Pancreatitis with Normal Serum IgG4 Concentrations: What Is the Correct Classification for Such Patients? Seiichi Hara, Terumi Kamisawa, Taku Tabata, Sawako Kuruma, Kazuro Chiba, and Satomi Koizumi
7.1
Introductory Remarks
Autoimmune pancreatitis (AIP), which was introduced from Japan to the rest of the world, is a distinctive type of pancreatitis. In 1995, a case was reported that showed pancreatic duct narrowing, pancreatic swelling, hypergammaglobulinemia, and positive autoantibodies, as well as marked responsiveness to steroids [1]. It subsequently became clear that in the condition now known as type 1 AIP, an elevated serum IgG4 concentration is observed in a high proportion of cases [2]. Extrapancreatic lesions are common in patients with type 1 AIP and may affect a wide range of organs with pathological features that are strikingly similar to those of the pancreas and tend to respond well to steroids. These pathological features include a marked lymphoplasmacytic infiltrate with an increased number of IgG4-positive plasma cells and a distinctive form of fibrosis that often assumes a storiform pattern. These multi-organ features are now recognized to comprise one systemic disease with the capability of affecting multiple organs in either a simultaneous fashion or, more commonly, in a metachronous manner. Thus, lymphoplasmacytic sclerosing pancreatitis (LPSP), as type 1 AIP is commonly known in the medical literature, is now regarded as the pancreatic lesion of IgG4-related disease (IgG4-RD) [3–5]. Broader experience with AIP led to the recognition of a form of this condition that is associated with normal IgG4 concentrations in the blood. In this chapter, we outline the clinical features of such cases, focusing on our own experience.
S. Hara • T. Kamisawa (*) • T. Tabata • S. Kuruma K. Chiba • S. Koizumi Department of Internal Medicine, Tokyo Metropolitan Komagome Hospital, 18-22, Honkomagome 3chome, Bunkyo-ku, Tokyo 113-8677, Japan e-mail: [email protected]
7.2
Autoimmune Pancreatitis: Types 1 and 2
Before the clear emergence of a second type of AIP and recognition of the need to designate the two currently recognized forms of AIP as types 1 and 2, the most common form of AIP in Japan came to be known as LPSP [6]. LPSP is characterized by extensive cellular infiltrates consisting of IgG4-positive plasma cells, T lymphocytes, fibrosis, and obliterative phlebitis. Neutrophils are typically absent in LPSP, and the inflammatory cell infiltrate tends to spare the pancreatic duct epithelium. The typical patient is an elderly man who presents with painless jaundice, i.e., minimal to no signs of acute pancreatitis. Other sclerosing extrapancreatic lesions are often present, such as in the biliary tree (IgG4-related sclerosing cholangitis) or salivary glands (IgG4-related sialadenitis, with submandibular or parotid gland involvement). In contrast to type 2 AIP, inflammatory bowel disease is almost never seen in LPSP [4, 5]. A European histopathological study detected neutrophil infiltration of the pa
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