Preliminary Research On The Clinical Characteristics Of IgG4-related Focal Autoimmune Pancreatitis

Background: IgG4-related disease(IgG4-RD),which has some characteristichistologic changes, is a newly described systemic entity in which the pathogenesisappears to involve autoimmune mechanisms. Most of the body organs,includingpancreas, gallbladder, bile duct, salivary glands, lacrimal gland, prostate, pituitary,thyroid, lung, kidney and skin, can be affected. In most previous researches, it wasthought that type1autoimmune pancreatitis (AIP),a member of IgG4-RDspectrum,was characterized by diffuse swelling of the pancreas.However, in recentyears, continuous cases of focal lesions of pancreas in AIP have been reported, whichmake focal autoimmune pancreatitis (f-AIP) attract increasingly more attentions.Sincethe single or multifocal lumps in pancreas that f-AIP presents are extremely similar topancreatic cancer,clinical misdiagnosis and unnecessary surgery treatment now andthen happen,causing the physical and mental suffering of patients and the delay oftreatment.Objective: Our research retrospectively analyzes the clinical features of localIgG4-RD patients,especially the features of f-AIP,in order to provide physicians moreefficient and precise methods to diagnose this entity and differentiate it from otherdiseases.Method: The patients who admitted to the first Bethune hospital of Jilinuniversity between January1st of2012and January1st of2015with serum IgG4level above normal were analyzed retrospectively in this study. Their major diagnosiswas recorded.Comprehensive data of the patients diagnosed as IgG4-RD during thethree years, including gender, age of onset, serological changes and involved organs,were recorded. We statistically compared serum IgG4level of IgG4-RD patients withthose of non-IgG4-RD patients who had abnormal serum IgG4level. For patients withtype1AIP, additionally record their onset symptoms, serum autoantibody level,pancreatic enzyme level, serum CA199level and their initial treatment strategy. Specifically illustrate the clinical features of f-AIP patients.There was1case of f-AIPcomplicated with Küttner’s tumor mimicking pancreatic cancer with neck metastasis.His imaging findings were analyzed and his biopsy specimens from labial gland andresected pancreas specimens were examined pathologically via HE staining andimmunohistochemical staining.Result: Of the55patients with higher serum IgG4level,26cases (47.27%) werediagnosed as IgG4-RD, and suspected IgG4-RD, pancreatitis with noautoimmunologic mechanism involved and other diseases were respectively5cases(9.09%),5cases(9.09%) and19cases(34.55%).No pancreatic cancer was foundin these cases. In the26IgG4-RD cases, all the patients were predominantlymiddle-aged, with a mean age of60.08±10.53, and the ratio of male to female was2.25:1. Laboratory tests showed high levels of serum IgG4, with an averageconcentration of1449±871mg/dl.Of all these IgG4-RD patients,24patients sufferedfrom IgG4-related AIP, in which15cases presented as pancreas involved alone and9cases were in combination with other organs involvement.1case of simpleperformance for Mikulicz’s disease and1case of Küttner’s tumor alone comprisedthe rest2IgG4-RD cases.On the aspect of the level of serum IgG4, the IgG4-RDpatients were statistically different from non-IgG4-RD patients with abnormalserum IgG4(except for the suspected cases). Jaundice and emaciation were the mostcommon clinical symptoms among the24AIP patients.The serological changes ofpancreatic enzyme level, serum CA199level and autoantibodies indexes could also beseen in some AIP patients.Most of the AIP patients (15/24,62.5%) tookcorticosteroids therapy alone as the initial treatment. The8f-AIP patients had somespecific features. In addition,there was one patient who suffered from f-AIPcomplicated with Küttner’s tumor mimicking pancreatic cancer with neckmetastasis.According to his abdominal CT imaging findings,he was tentativelydiagnosed as pancreatic cancer.However, his specimens from pancreatic neoplasmand labial gland showed abundant infiltration of lymphoplasmacytes and fibrosis viaHE staining, and numerous infiltration of IgG-positive or IgG4-positive plasma cellsvia immunohistochemical staining.This patient also had a high level of serum IgG4 (3270mg/dl) as well as a pretty good response to steroid treatment.All these abovefeatures met with the diagnosis of IgG4-RD.As a result,pancreatic cancer wasfinally ruled out.Conclusion: Elevated serum IgG4level can be seen in a variety of diseases, andit is much more apparent in IgG4-RD.As a result, the patients with mild change ofserum IgG4level should be carefully ruled out for other possible diseases,and for thepatients with severely high serum IgG4level, it is so important that they shouldfurther take imaging and histological examination.We also ought to pay attention tothe general condition in order to improve diagnostic accuracy of IgG4-RD. Since thedifferentiation of f-AIP from PC is very difficult and their treatment are very different,we suggest that AIP should always be considered in case of a focal pancreatic mass.Patients with pancreatic mass should routinely test serum IgG4level, combined withimaging and histological findings in order to avoid unnecessary surgery.