Autoimmune pancreatitis overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Iqra Qamar M.D.[2]
Overview
Historical Perspective
The concept of pancreas and pancreatic duct was first described by Johannes Wirsung of Padua in 1642. In 1761, Giovanni Morgagni described the clinical syndrome of severe upper abdominal pain, vomiting, and collapse. He is also credited with the earliest pathological recognition of cancer of the pancreas. In 1948, Eliason and Welty described distal pancreatectomy (DP). In 1980, Beger described duodenal-preserving pancreatic head resection (DPPHR) technique for chronic pancreatitis to decrease the morbidity of pancreatic head resection. In 1961, Sarles proposed autoimmunity as a pathogenetic mechanism of pancreatitis. In 1995, Yoshida proposed the term "autoimmune pancreatitis" for the first time. Autoimmune pancreatitis is also known as primary inflammatory pancreatitis, lymphoplasmacytic sclerosing pancreatitis, pseudotumorous pancreatitis, chronic pancreatitis with irregular narrowing of the main pancreatic duct, idiopathic chronic pancreatitis, and nonalcoholic duct destructive chronic pancreatitis. In 2009, the two types of autoimmune pancreatitis were first identified such as type 1 (lymphoplasmacytic sclerosing pancreatitis) and type 2 (idiopathic duct-centric pancreatitis).
Classification
Autoimmune pancreatitis may be classified into two types; Type 1 AIP and Type 2 AIP or idiopathic duct-centric pancreatitis. Type 1 AIP meets the HISORt criteria, involves pancreas as one part of a systemic IgG4-positive disease. Type 2 consists of granulocytic lesions, does not involve IgG4-positive cells, has no systemic involvement, and is usually associated with inflammatory bowel disease.
Pathophysiology
Th1-type CD4+ T cells are thought to play an important role in the pathogenesis of autoimmune pancreatitis (AIP) via autoimmune reaction against carbonic anhydrase type II or lactoferrin. Autoimmune pancreatitis may involve fibrosis of peripancreatic vessels leading to obliterative vasculitis and phlebitis similar to that occuring in pancreatic cancer. Autoimmune pancreatitis may be associated with systemic autoimmune conditions such as IgG4-associated cholangitis, chronic sclerosing sialadenitis (Küttner's tumor), Mikulicz's disease (IgG4-related plasmacytic exocrinopathy), mediastinal fibrosis, adenopathy, chronic periaortitis, idiopathic retroperitoneal fibrosis, tubulointerstitial nephritis, IgG4-associated pseudolymphoma, ulcerative colitis and hypergammaglobulinemia. Diffuse pancreatic gland enlargement may be seen on gross examination. Microscopic findings suggestive of autoimmune pancreatitis may include Interlobular ducts surrounded by the infiltration of inflammatory cells and fibrosis. Immunohistochemistry stains may show CD4+ T cells (mainly), some CD8+ T cells, B cells and HLA-DR antigen expression on pancreatic duct or acinar cells.
Causes
Autoimmune pancreatitis is idiopathic in origin and has no clear etiology. Autoimmune pancreatitis is thought to be due to some autoimmune reaction against pancreas and might be associated with other autoimmune diseases.
Differentiating Autoimmune pancreatitis from Other Diseases
Autoimmune pancreatitis needs to be differentiated from other diseases such as alcoholic chronic pancreatitis, pancreatic cancer, chronic pancreatitis, inflammatory bowel disease, dumping syndrome, celiac disease, Whipple's disease, tropical sprue and colon carcinoma.
Epidemiology and Demographics
Autoimmune pancreatitis is a world wide entitiy but it's incidence has been found to be recently increased in Japan. In North America, 2.5% of pancreatoduodenectomies are done because of AIP being misdiagnosed as pancreatic cancer. The mean age of patients with AIP is 59 yr (range, 45–75 yr). In autoimmune pancreatitis, the male-to-female ratio was found to be 15:2. Autoimmune pancreatitis usually involves elderly male population.
Risk Factors
Screening
Natural History, Complications, and Prognosis
Diagnosis
Diagnostic Criteria
History and Symptoms
Physical Examination
Laboratory Findings
Electrocardiogram
X-ray
Ultrasound
CT scan
MRI
Other Imaging Findings
Other Diagnostic Studies
Treatment
Medical Therapy
Surgery
Surgery is usually considered when pain management fails with medical and endoscopic therapies. The goals of surgery include effective pain relief, and to preserve long-term pancreatic function. Surgery for chronic pancreatitis tends to be divided into two areas - resectional and drainage procedures. Dilated pancreatic duct may be managed with lateral pancreaticojejunostomy (LPJ) and lateralpancreaticojejunostomy with localized pancreatic head resection. Nondilated pancreatic duct is usually managed with pancreaticoduodenectomy, duodenal-preserving pancreatic head resection (DPPHR), distal pancreatectomy (DP) and total pancreatectomy (TP).