In cases of systemic manifestation of AIP, the pathologic features are similar in other organs.Although the exact mechanism explaining the clinical manifestations of autoimmune pancreatitis remain for an important part obscure, most professionals would agree that the development of IgG4 antibodies, recognizing an epitiope on the membrane of pancreatic ancinar cells is an important factor in the pathophysiology of the disease. These antibodies are postulated to provoke an immune response against these ancinar cells resulting in pancreatic inflammation and destruction. Knowing the auto-antigens involved would allow early diagnosis of the disease, its differentiation from a diagnosis of pancreatic cancer, and potentially even prevention, but unfortunately these remain obscure. An earlier publication suggested that the human ubiquitin-protein ligase E3 component n-recognin 2 (UBR2) was an important antigen  but follow up studies suggested this finding is likely to be an artifact. Hence improved diagnosis, understanding and treatment of autoimmune pancreatitis awaits the identification of the auto-antigens involved. Diagnosis
Criteria
Most recently the fourteenth Congress of the International Association of Pancreatology developed the International Consensus Diagnostic Criteria (ICDC) for AIP. The ICDC emphasizes five cardinal features of AIP which includes the imaging appearance of pancreatic parenchyma and the pancreatic duct, serum IgG4 level, other organ involvement with IgG4-related disease, pancreatic histology and response to steroid therapy.In 2002, the Japanese Pancreas Society proposed the following diagnostic criteria for autoimmune pancreatitis:
I. Pancreatic imaging studies show diffuse narrowing of the main pancreatic duct with irregular wall (more than 1/3 of length of the entire pancreas). II.
Autoimmune Pancreatitis (AIP) is an increasingly recognized  type of chronic pancreatitis that can be difficult to distinguish from pancreatic carcinoma but which responds to treatment with corticosteroids, particularly prednisone. Although autoimmune pancreatitis is quite rare, it constitutes an important clinical problem for both patients and their clinicians: the disease commonly presents itself as a tumorous mass which is diagnostically indistinguishable from pancreatic cancer, a disease that is much more common in addition to being very dangerous. Hence, some patients undergo pancreatic surgery, which is associated to substantial  mortality and morbidity, out of the fear by patients and clinicians to undertreat a malignancy. However, surgery is not a good treatment for this condition as AIP responds well to immunosuppressive treatment. There are two categories of AIP: Type 1 and Type 2, each with distinct clinical profiles. Type 1 AIP is now regarded as a manifestation of IgG4-related disease, and those affected have tended to be older and to have a high relapse rate. Type 1 is associated with pancreatitis, Sjogren syndrome, Primary sclerosing cholangitis and Inflammatory bowel disease. Patients with Type 2 AIP do not experience relapse, tend to be younger and not associated with systemic disease. AIP occurring in association with an autoimmune disorder has been referred to as "secondary" or "syndromic" AIP. AIP does not affect long-term survival. Signs and symptoms
Autoimmune pancreatitis may cause a variety of symptoms and signs, which include pancreatic and biliary (bile duct) manifestations, as well as systemic effects of the disease.