Autoimmune pancreatitis: instrumental diagnosis.

Autoimmune pancreatitis (AIP) is an unusual type of chronic pancreatitis having an underlying autoimmunity mechanism. Lymphoplasmacytic infiltration and fibrosis on histology, and elevated IgG levels or detected autoantibodies on laboratory data support the concept of AIP. Periductal lymphoplasmacytic infiltration and fibrosis, its preferential occurrence in the pancreatic head, and venulitis characterize autoimmune pancreatitis [1]. AIP should be distinguished from alcoholic chronic pancreatitis because steroid therapy for the former type is effective, morphologic changes are reversible, and pancreatic function can return to normal levels [2]. Difficulties can also arise in differentiating AIP from pancreatic carcinoma, as AIP predominantly affects elderly men, who frequently present with jaundice but without the features of acute pancreatitis, while there can be elevation of serum tumor markers. Other than clinical findings, there are also imaging findings which can be confusing: stenosis of the bile duct, segmental pancreatic enlargement or narrowing of the main pancreatic duct, and angiographic abnormalities which can cause confusion in the differential diagnosis between AIP and pancreatic carcinoma [3]. In fact, in many cases, patients with the focal form of AIP undergo surgery with a clinical and radiological diagnosis of pancreatic carcinoma [4, 5]. In order to obtain a correct diagnosis it is necessary to investigate all available information.