Autoimmune pancreatitis (AIP), characterized by an autoimmune phenomenon of prominent lymphocytes, IgG4-bearing plasma cell infiltration and storiform fibrosis, has been widely reported as a specific type of chronic pancreatitis. Typical image findings of this disease are reported as diffuse pancreatic swelling and a capsule-like rim on CT or MRI. However, AIP presents with a variable morphology, such as focal, segmental and multifocal swellings. Because imaging findings for AIP can look like those of pancreatic cancer, AIP has often been treated with unnecessary surgical resection. In addition, AIP is complicated by the involvement of various other organs besides the pancreas that show lymphoplasmacytic infiltration and fibrosis. These are frequently misdiagnosed as inherent lesions of corresponding organs. Furthermore, these extra-pancreatic lesions show systemic distribution and share common features of IgG4- bearing plasma cell infiltration as well as favorable responses to corticosteroid, indicating the presence of systemic condition, IgG4-related diseases. AIP is now recognized as an IgG4-related disease. Detailed evaluations of imaging findings of CT, MRI and Gallium-67 (Ga-67) scintigraphy for the involvement of these various organs are useful for a correct diagnosis of this systemic disease.
Keywords: Autoimmune pancreatitis, extra-pancreatic lesion, IgG4, CT, MRI, Ga-67 scintigraphy, Pancreatitis, Hilar Lymphadenopathy, Pulmonary Abnormalities, Renal Lesions, Retroperitoneal Lesions, Ligamentum teres
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