Type 2 Autoimmune Pancreatitis (Idiopathic Duct-Centric Pancreatitis) Highlighting Patients Presenting as Clinical Acute Pancreatitis: A Single-Center Experience

Clinical features and long-term outcomes of patients with type 2 autoimmune pancreatitis

OBJECTIVES

Type 2 is a rare form of autoimmune pancreatitis (AIP). Despite being considered a benign disease, only few studies with limited sample size and short follow-up have been published on type 2 AIP. The aim of this observational study was to evaluate long-term outcomes, such as the risk of relapse, pancreatic insufficiency and cancer in a large type 2 AIP cohort with long follow-up.

METHODS

Patients with definitive or probable diagnosis of type 2 AIP by International Consensus Diagnostic Criteria (ICDC) present in our prospectively maintained database since 1995 at 31.12.2021 were identified. All patients were clinically evaluated during the year 2022. Clinical, radiological, serological, and pathological data were evaluated.

RESULTS

Eighty-eight out of 420 patients present in the database (21%) were diagnosed with type 2 AIP (mean age 33.5 ± 13.5 years). According to the ICDC, 21 patients (23.8%) had a definitive and 67 (76.2%) a probable diagnosis of type 2 AIP. The mean follow-up was 9.2 ± 7.1 years (range 1-27 years). No differences were observed when comparing patients with definitive and probable type 2 AIP diagnosis. Concomitant IBD was reported in 77 patients (87.5%). The probability of disease relapse was lower in patients treated with steroids versus surgery (at 5 years 13% vs. 33%; p = 0.038) but this difference was not statistically significant at multivariable analysis. The risk of endocrine or severe exocrine insufficiency was low (5% and 25%). Four extra-pancreatic malignancies (5%) were diagnosed, none pancreatic. One patient died in a car accident.

CONCLUSIONS

Type 2 AIP has benign long-term clinical outcomes. Mortality and cancer rates are low and no specific follow-up is needed after radiological remission.

Autoimmune pancreatitis type 2 (idiopathic duct-centric pancreatitis): A comprehensive review

Autoimmune pancreatitis (AIP) is an uncommon fibro-inflammatory disorder precipitated by autoimmune/inflammatory reactions. Currently, there are two clinical subtypes of AIP (type 1 [AIP-1] and type 2 [AIP-2]) that correspond to two histologic descriptors (lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric pancreatitis, respectively). While our understanding of AIP-1 has evolved considerably over the years, little is known about AIP-2 due to its rarity, often leading to misdiagnosis, delayed treatment, and even unnecessary surgical resection. Compared to AIP-1, AIP-2 exhibits distinct clinical and histologic features. Because AIP-2 is a pancreas-restricted disease without a specific serum marker, the evaluation of histologic features (e.g., granulocytic epithelial lesions) is essential for an accurate diagnosis. Patients with AIP-2 respond well to glucocorticoids, with anti-tumor necrosis factor-alpha antibodies as a promising alternative therapy. The prognosis of AIP-2 is generally favorable and relapse is uncommon. Here, we provide an overview of our current knowledge on the clinical features, diagnosis, therapeutic regimens, prognosis, and putative mechanisms underlying AIP-2. Notably, the diagnostic differentiation between AIP-2, especially the mass-forming/focal type, and pancreatic cancer is important, but challenging. In this regard, endoscopic ultrasound-guided core biopsy has a key role, but novel diagnostic markers and modalities are clearly needed.

A Clinical and Pathophysiological Overview of Intestinal and Systemic Diseases Associated with Pancreatic Disorders: Causality or Casualty?

The relationship between chronic intestinal disease, including inflammatory bowel disease (IBD) and celiac disease (CelD), and pancreatic disorders has been little investigated. Although an increased risk of acute pancreatitis (AP), exocrine pancreatic insufficiency with or without chronic pancreatitis, and chronic asymptomatic pancreatic hyperenzymemia have been described in these patients, the pathogenetic link remains unclear. It may potentially involve drugs, altered microcirculation, gut permeability/motility with disruption of enteric-mediated hormone secretion, bacterial translocation, and activation of the gut-associated lymphoid tissue related to chronic inflammation. In addition, the risk of pancreatic cancer seems to be increased in both IBD and CelD patients with unknown pathogenesis. Finally, other systemic conditions (e.g., IgG4-related disease, sarcoidosis, vasculitides) might affect pancreatic gland and the intestinal tract with various clinical manifestations. This review includes the current understandings of this enigmatic association, reporting a clinical and pathophysiological overview about this topic.

Characteristics of mass-forming autoimmune pancreatitis commonly misdiagnosed as a malignant tumor

Objective

This study aimed to explore the clinical characteristics and differential diagnosis of patients with autoimmune pancreatitis (AIP) and pancreatic cancer to prevent misdiagnosis and mistreatment.

Methods

The clinical data of patients with AIP with suspected pancreatic or bile duct malignancy and pancreatic cancer were retrospectively analyzed. The risk factors and the diagnostic value of IgG4 and Tbil levels before treatment for AIP was investigated. Moreover, the imaging features and response to hormone therapy were analyzed.

Results

AIP was commonly observed in men. Compared to patients with pancreatic cancer, the incidence of poor appetite and weight loss and carbohydrate antigen 19-9 (CA19-9) level was lower in patients with AIP, while the immunoglobulin G4 (IgG4) level was higher (p < 0.05). After treatment, the IgG4 and CA19-9 levels in patients with AIP were decreased (p < 0.001). IgG4 level before treatment (OR = 2.452, 95%CI: 1.180-5.096, P = 0.016) and total bilirubin (Tbil) level before treatment (OR = 0.992, 95%CI: 0.985-0.998, P = 0.013) were independent risk factors of AIP. Furthermore, the diagnostic value of IgG4 level before treatment, Tbil level before treatment, IgG4/Tbil before treatment, and a combination of these indicators was high. Moreover, 15 (68.18%) patients with AIP had space-occupying lesions of the pancreas, and 16 (72.73%) had autoimmune cholangitis. Most patients with AIP were sensitive to hormone therapy.

Conclusions

The Tbil and IgG4 levels, imaging findings, and hormone therapy reactivity could differentiate AIP from pancreatic cancer. A combination of IgG4, Tbil, and IgG4/Tbil before treatment might be a promising diagnostic biomarker for AIP.

Autoimmune Pancreatitis: From Pathogenesis to Treatment

Autoimmune pancreatitis (AIP) is a rare disease. The diagnosis of AIP is difficult and should be made by a comprehensive evaluation of clinical, radiological, serological, and pathological findings. Two different types of AIP have been identified: autoimmune pancreatitis type 1 (AIP-1), which is considered a pancreatic manifestation of multiorgan disease related to IgG4, and autoimmune pancreatitis type 2 (AIP-2), which is considered a pancreas-specific disease not related to IgG4. Although the pathophysiological conditions seem to differ between type 1 and type 2 pancreatitis, both respond well to steroid medications. In this review, we focused on the pathogenesis of the disease to develop a tool that could facilitate diagnosis and lead to the discovery of new therapeutic strategies to combat autoimmune pancreatitis and its relapses. The standard therapy for AIP is oral administration of corticosteroids. Rituximab (RTX) has also been proposed for induction of remission and maintenance therapy in relapsing AIP-1. In selected patients, immunomodulators such as azathioprine are used to maintain remission. The strength of this review, compared with previous studies, is that it focuses on the clear difference between the two types of autoimmune pancreatitis with a clearly delineated and separate pathogenesis. In addition, the review also considers various therapeutic options, including biologic drugs, such as anti-tumor necrosis factor (TNF) therapy, a well-tolerated and effective second-line therapy for AIP type 2 relapses or steroid dependence. Other biologic therapies are also being explored that could provide a useful therapeutic alternative to corticosteroids and immunosuppressants, which are poorly tolerated due to significant side effects.

Autoimmune Pancreatitis and Immunoglobulin G4-related Sclerosing Cholangitis: Past, Present, and Future

The emergence of glucocorticoid-responsive autoimmune pancreatitis (AIP) and IgG4-related sclerosing cholangitis (IgG4-SC), a new disease entity, has attracted considerable interest within the international gastroenterology community. The typical manifestations of AIP/IgG4-SC are obstructive jaundice and pancreatic enlargement in the elderly, which may mimic the presentations of pancreatobiliary malignancies. The timely diagnosis of AIP/IgG4-SC can lead to adequate glucocorticoid treatment, whereas a misdiagnosis can result in unnecessary major surgery. The diagnostic criteria used to diagnose AIP include several cardinal features of AIP that can be detected via pancreatic parenchymal imaging, ductal imaging, serum IgG4 levels, histopathology, other organ involvement, and response to glucocorticoid therapy. The differential diagnosis of AIP/IgG4-SC may include pancreatobiliary malignancies and primary sclerosing cholangitis. Although most patients with AIP/IgG4-SC respond well to glucocorticoid therapy, there is a frequent relapse of the disease in the long term. This review describes the evolution of the concept of AIP and IgG4-related disease, including the development of diagnostic criteria, discusses the current practice for diagnosis and treatment, and suggests prospects for research.

Prevalence and clinical features of patients with autoimmune pancreatitis and inflammatory bowel disease: A systematic review and meta-analysis

BACKGROUND AND AIM

Autoimmune pancreatitis (AIP) and inflammatory bowel disease (IBD) are categorized into immune-mediated inflammatory disorders (IMIDs). While AIP is a pancreato-biliary IMID with an increased incidence and prevalence among patients with IBD, its features are still unclear. This systematic review and meta-analysis aims to assess the prevalence and clinical characteristics of AIP-IBD patients.

METHODS

Electronic databases were searched to identify observational studies assessing AIP and IBD. The primary outcome was the prevalence of IBD among AIP patients, and vice versa. Secondary outcomes included clinical findings and outcomes of each IMID in AIP-IBD patients. The pooled rate of each outcome was determined using a random effects model.

RESULTS

For primary outcomes, 40 observational studies with 4031 AIP patients were included and the pooled prevalence of IBD was 10.5% (95% CI 7.2-15.0%). Meanwhile, five studies with 10,551 IBD patients were included and the pooled prevalence of AIP was 0.6% (95% CI 0.2-1.9%). For secondary outcomes, 53 observational studies with 469 AIP-IBD patients were assessed. The rates of type 2 AIP and ulcerative colitis were 79.2% (95% CI 69.1-86.6%) and 74.8% (95% CI 68.2-80.4%), respectively. We also demonstrated AIP-IBD patients were at a significant increased risk of AIP recurrence and colectomy compared with patients with either AIP or IBD (RR = 1.9, 95% CI 1.1-3.1 and P = 0.014 and RR = 3.7, 95% CI 1.9-6.9, P < 0.001, respectively).

CONCLUSIONS

Our meta-analysis reported the prevalence of AIP-IBD patients and demonstrated patients with both IMIDs had a high risk of poor outcomes.

Granulocytic epithelial lesion (GEL) in heterotopic pancreas

BACKGROUND

The diagnosis of type 2 autoimmune pancreatitis (AIP) is dependent on typical radiologic imaging and the presence of the granulocytic epithelial lesion (GEL), which is characterized by ductal neutrophilic infiltration with or without neutrophilic acinar infiltration.

METHODS

We evaluated GEL and related clinicopathologic factors in 165 resected heterotopic pancreata (HPs) [57 gastric (35%), 56 duodenal (34%), 30 omental (18%), and 22 jejunal (13%)] and 29 matched orthotopic pancreata routinely examined during surgery.

RESULTS

GEL was noted in 8% (13/165) of HPs, including ductal epithelial (6/13, 46%) and intraluminal (8/13, 62%) neutrophilic infiltrations. However, there was no GEL in orthotopic pancreata. Abdominal pain was observed in 6 (46%) patients with GEL-positive HPs. GEL was more commonly observed in HPs having symptoms (p = 0.029), a larger size (p = 0.028), and an infiltrative growth pattern (p = 0.006). In addition, periductal lymphoplasmacytic infiltration and fibrosis (both p < 0.001), interstitial fibrosis (p = 0.017), acinar neutrophilic infiltration (p = 0.032), venulitis (p = 0.050), acinar ductal metaplasia (ADM; p = 0.040), and pancreatic intraepithelial neoplasia/intraductal papillary mucinous neoplasms (PanIN/IPMN; p < 0.001) were more commonly seen in HPs with GEL than in those without GEL. Inflammatory bowel disease was present only in one patient with GEL-negative HP.

CONCLUSIONS

GELs are detected in a subset of HPs without clinical evidence of AIP. Therefore, for the diagnosis of AIP, GEL should be carefully interpreted with the context of other histologic, clinical, and radiologic findings.

Pancreatic Disorders in Patients with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) can involve multiple organ systems, and pancreatic manifestations of IBD are not uncommon. The incidence of several pancreatic diseases is more frequent in patients with Crohn's disease and ulcerative colitis than in the general population. Pancreatic manifestations in IBD include a heterogeneous group of disorders and abnormalities ranging from mild, self-limited disorders to severe diseases. Asymptomatic elevation of amylase and/or lipase is common. The risk of acute pancreatitis in patients with IBD is increased due to the higher incidence of cholelithiasis and drug-induced pancreatitis in this population. Patients with IBD commonly have altered pancreatic histology and chronic pancreatic exocrine dysfunction. Diagnosing acute pancreatitis in patients with IBD is challenging. In this review, we discuss the manifestations and possible causes of pancreatic abnormalities in patients with IBD.

The features and clinical outcomes of inflammatory bowel disease associated with autoimmune pancreatitis: A greater awareness is needed

The prevalence of inflammatory bowel disease (IBD) has been described in 5% to 40% of autoimmune pancreatitis (AIP) patients. The aim of our study was to evaluate the prevalence, endoscopic features, and outcome of IBD in association with AIP.A retrospective analysis including all consecutive patients with AIP and a histological diagnosis of IBD from 2010 to 2020 was performed. Demographical data, AIP, and IBD features, as well as clinical course, were recorded.Among 267 AIP patients, 45 were diagnosed with ulcerative colitis (UC) (27 men, mean age 31.6), all with a diagnosis of type 2 AIP. The most frequent presentation of AIP was acute pancreatitis (55.5%). Both diffuse (51.1%) and focal (48.9%) pancreatic involvement were observed. The AIP relapse rate was 11.1% over a mean follow-up of 55 months. In 69% of patients, the interval time between the diagnosis of AIP and UC was <1 year. When UC was present at AIP onset, UC was in clinical remission in 50% of patients. Fecal calprotectin levels, when available, were elevated in 86.6% of these patients. Mostly, mild-moderate pancolitis was initially diagnosed (55.5%). During follow-up, escalation therapy for UC was required in 40% of patients after a mean time of 45 months. Two patients (4.4%) underwent colectomy.The prevalence of UC in AIP patients was 17%. Mild pancolitis with a low rate of colectomy was found. Greater awareness is needed to avoid a delayed diagnosis of UC, and the dosage of fecal calprotectin levels could have a role in this setting.

Type 2 Autoimmune Pancreatitis: Consensus and Controversies

Autoimmune pancreatitis (AIP) has attracted much attention in the last two decades, and due to the diagnostic value of immunoglobulin G4 (IgG4), the number of cases diagnosed in clinical practice has markedly increased. However, in contrast to prototypic IgG4-related type 1 AIP, a minor subtype of AIP, referred to as type 2 AIP, is less widely known and has thus not yet been characterized in detail. Type 2 AIP is unrelated to IgG4 and is a completely distinct entity from type 1 AIP. One confusing factor is that the two types of AIP share patterns of clinical presentation (e.g., acute pancreatitis and painless jaundice) and imaging abnormalities (e.g., diffuse or segmental enlargement). Since there are currently no established serum markers, the diagnosis of type 2 AIP is highly challenging and requires the tissue confirmation of neutrophilic injury to the pancreatic ducts, a finding designated as a granulocytic epithelial lesion. Approximately one-third of cases are associated with inflammatory bowel disease, particularly ulcerative colitis; however, the pathological relationship between these two conditions has not yet been clarified. Unanswered questions relate to its pathophysiology, the potential development of a similar granulocytic injury in other organs, and the characteristics of pediatric cases. This review summarizes consensus and controversies surrounding type 2 AIP, with the aim of increasing awareness and highlighting the unmet needs of this underrecognized condition.

Multifocal autoimmune pancreatitis: A retrospective study in a single tertiary center of 26 patients with a 20-year literature review

BACKGROUND

Multifocal-type autoimmune pancreatitis (AIP), sometimes forming multiple pancreatic masses, is frequently misdiagnosed as pancreatic malignancy in routine clinical practice. It is critical to know the imaging features of multifocal-type AIP to prevent misdiagnosis and unnecessary surgery. To the best of our knowledge, there have been no studies evaluating the value of diffusionweighted imaging (DWI), axial fat-suppressed T1 weighted image (T1WI), and dynamic contrast enhanced-computed tomography (DCE-CT) in detecting the lesions of multifocal-type AIP.

AIM

To clarify the exact prevalence and radiological findings of multifocal AIP in our cohorts and compare the sensitivity of DWI, axial fat-suppressed T1WI, and DCE-CT for detecting AIP lesions. We also compared radiological features between multifocal AIP and pancreatic ductal adenocarcinoma with several key imaging landmarks.

METHODS

Twenty-six patients with proven multifocal AIP were retrospectively included. Two blinded independent radiologists rated their confidence level in detecting the lesions on a 5-point scale and assessed the diagnostic performance of DWI, axial fat-suppressed T1WI, and DCE-CT. CT and magnetic resonance imaging of multifocal AIP were systematically reviewed for typical imaging findings and compared with the key imaging features of pancreatic ductal adenocarcinoma.

RESULTS

Among 118 patients with AIP, 26 (22.0%) had multiple lesions (56 lesions). Ulcerative colitis was associated with multifocal AIP in 7.7% (2/26) of patients, and Crohn’s disease was present in 15.3% (4/26) of patients. In multifocal AIP, multiple lesions, delayed homogeneous enhancement, multifocal strictures of the main pancreatic duct, capsule-like rim, lower apparent diffusion coefficient values, and elevated serum Ig4 level were observed significantly more frequently than pancreatic ductal adenocarcinoma, whereas the presence of capsule-like rim in multifocal-type AIP was lower in frequency than total AIP. Of these lesions of multifocal AIP, DWI detected 89.3% (50/56) and 82.1% (46/56) by the senior and junior radiologist, respectively.

CONCLUSION

Multifocal AIP is not as rare as previously thought and was seen in 22.0% of our patients. The diagnostic performance of DWI for detecting multifocal AIP was best followed by axial fat-suppressed T1WI and DCE-CT.

Risks and characteristics of pancreatic cancer and pancreatic relapse in autoimmune pancreatitis patients

BACKGROUND AND AIM

We examined the differences in the risks and characteristics of pancreatic relapse (PR) and pancreatic cancer (PC) in patients with autoimmune pancreatitis (AIP).

METHODS

We retrospectively reviewed 123 type 1 AIP patients with a median follow-up of 55 months (interquartile range, 27-98). The following items were evaluated: (i) cumulative relapse rates and risk factors, (ii) the incidence of PC, (iii) PR versus PC, and (iv) outcomes after the appearance of morphological changes in the pancreas (focal enlargement, apparent mass lesions, or main pancreatic duct dilation).

RESULTS

(i) The cumulative PR rates were 1.7% within 1 year, 11.5% within 3 years, and 22.6% within 5 years. Lack of maintenance therapy, IgG4-related sclerosing cholangitis, and IgG4-related kidney disease were identified as independent predictors of relapse. (ii) Two patients (1.6%) were diagnosed with PC at 17 and 22 months after initial AIP diagnosis. (iii) Thirteen (59.1%) and four (18.2%) patients with PR had focal enlargement and main pancreatic duct dilation, respectively. The median CA19-9 level at initial diagnosis was significantly higher in PC patients (21 vs 220.5 U/mL, P = 0.014). (iv) Eight PR patients underwent endoscopic ultrasound-guided fine-needle aspiration, none of whom had malignant findings. PC was diagnosed by ultrasound-guided fine-needle aspiration in both cancer patients.

CONCLUSIONS

Although the incidence of PC is low, it may mimic PR in AIP patients. Surveillance is important, and when morphological changes occur, biopsy and evaluation of serum IgG4 and CA19-9 levels (particularly if the levels were high before) should be considered.

Prevalence of histological features resembling autoimmune pancreatitis in neoplastic pancreas resections

AIMS

Types 1 and 2 autoimmune pancreatitis (AIP) can mimic pancreatic neoplasia. Due to the small quantity of tissue in mass-targeted pancreas biopsies, inflammatory features may raise the differential of AIP. However, the frequency of AIP-like histology in neoplastic pancreas is not well characterised. Therefore, the specificity of inflammatory lesions on biopsy with respect to the diagnosis of AIP is uncertain.

METHODS AND RESULTS

Neoplastic pancreas resections performed at our institution between 2008 and 2019 were retrospectively reviewed. Features of AIP types 1 and 2 were assessed in the non-neoplastic areas. If features of immunoglobulin (Ig)G4-associated AIP were seen, IgG4 immunohistochemistry was performed. We identified 163 neoplastic pancreas resections. Of these, 34 had one or more types of inflammatory lesions in non-neoplastic pancreatic tissue. Dense lymphoplasmacytic inflammation mimicking type 1 AIP was found in six cases with mild to moderately increased IgG4-positive plasma cells. Neutrophilic infiltrates in small intralobular ducts were found in 20 cases. Mild extralobular ductitis or duct microabscess was found in 10 specimens. Marked neutrophilic duct destruction that resembled granulocytic epithelial lesions was found in 12 cases. Some cases showed multiple features.

CONCLUSION

Approximately 20% of neoplastic pancreas resections showed focal areas that could raise the differential of AIP. More cases showed neutrophilic predominant inflammation as seen in type 2 autoimmune pancreatitis, compared to dense lymphoplasmacytic infiltrates seen in type 1 AIP. Pathologists must be cautious when making a diagnosis of AIP on biopsy tissue based on histological findings alone.

Acute Pancreatitis as the Initial Manifestation in 2 Cases of COVID-19 in Wuhan, China

Clinical data on coronavirus disease 2019 (COVID-19) with pancreatic injury are extremely limited. An acute manifestation of acute pancreatitis in COVID-19 has not been reported. We describe here 2 cases of COVID-19 with acute pancreatitis as the initial manifestation in Wuhan, China. Patient 1 died despite maximal mechanical ventilatory support and circulation support, while patient 2 was finally discharged after showing significant improvement. Low T cells in peripheral blood may indicate a poor outcome.

Sialadenitis in a patient with ulcerative colitis and autoimmune pancreatitis type 2

Autoimmune pancreatitis (AIP) is a distinct form of chronic pancreatitis that has been increasingly recognised over the last decades and shows a good response to corticosteroid treatment. Two different forms of AIP have been characterized. Type 1 AIP is the pancreatic manifestation of IgG4-related disease and often affects multiple organ systems. In contrast, type 2 AIP is confined to the pancreas and involvement of extra-pancreatic organs has previously only very rarely been reported, except for an association with inflammatory bowel disease. The hallmark lesion of type 2 AIP is the granulocyte epithelial lesion (GEL), showing infiltration of neutrophilic granulocytes in the epithelium of pancreatic ducts and their accumulation in the duct lumen. We present a 61-year-old female patient who underwent pancreaticoduodenectomy with a postoperative histological diagnosis of type 2 AIP. Three months later, she underwent colectomy and was diagnosed with ulcerative colitis. One year later, she presented with swelling and pain of the right-sided submandibular salivary gland which was resected. Sialadenitis with lymphoplasmacytic inflammation, obliterative phlebitis, fibrosis and frequent accumulation of neutrophilic granulocytes in ducts, reminiscent of GELs, without IgG4-positivity or epitheloid cell granulomas, was found. Later, she presented with swelling and pain related to the left-sided submandibular gland, which resolved after steroid treatment. We describe the clinical, histological and immunohistochemical findings in this patient. It may be hypothesized that the sialadenitis may represent a rare extrapancreatic manifestation of, alternatively a rare association with, type 2 AIP or ulcerative colitis.

The Etiology of Pancreatic Manifestations in Patients with Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an idiopathic chronic and recurrent condition that comprises Crohn's disease and ulcerative colitis. A pancreatic lesion is one of the extraintestinal lesions in patients with IBD. Acute pancreatitis is the representative manifestation, and various causes of pancreatitis have been reported, including those involving adverse effects of drug therapies such as 5-aminosalicylic acid and thiopurines, gall stones, gastrointestinal lesions on the duodenum, iatrogenic harm accompanying endoscopic procedures such as balloon endoscopy, and autoimmunity. Of these potential causes, autoimmune pancreatitis (AIP) is a relatively newly recognized disease and is being increasingly diagnosed in IBD. AIP cases can be divided into type 1 cases involving lymphocytes and IgG4-positive plasma cells, and type 2 cases primarily involving neutrophils; the majority of AIP cases complicating IBD are type 2. The association between IBD and chronic pancreatitis, exocrine pancreatic insufficiency, pancreatic cancer, etc. has also been suggested; however, studies with high-quality level evidence are limited, and much remains unknown. In this review, we provide an overview of the etiology of pancreatic manifestation in patients with IBD.