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

Autoimmune pancreatitis: Biopsy interpretation and differential diagnosis

Autoimmune pancreatitis (AIP) is classified into type 1 (IgG4-related) and type 2 (IgG4-unrelated) and the interpretation of pancreatic biopsy findings plays a crucial role in their diagnosis. Needle biopsy of type 1 AIP in the acute or subacute phase shows a diffuse lymphoplasmacytic infiltrate, storiform fibrosis, obliterative phlebitis, and the infiltration of many IgG4-positive plasma cells. In a later phase, changes become less inflammatory and more fibrotic, making interpretations more challenging. Confirmation of the lack of 'negative' findings that are unlikely to occur in type 1 AIP (e.g., neutrophilic infiltration, abscess) is important to avoid an overdiagnosis. The number of IgG4-positive plasma cells increases to >10 cells/high-power field (hpf), and the IgG4/IgG-positive plasma cell ratio exceeds 40 %. However, these are minimal criteria and typical cases show >30 positive cells/hpf and a ratio >70 % even in biopsy specimens. Therefore, cases with a borderline increase in this number or ratio need to be diagnosed with caution. In cases of ductal adenocarcinoma, the upstream pancreas rarely shows type 1 AIP-like changes; however, the ratio of IgG4/IgG-positive plasma cells is typically <40 %. Although the identification of a granulocytic epithelial lesion (GEL) is crucial for type 2 AIP, this finding needs to be interpreted in conjunction with a background dense lymphoplasmacytic infiltrate. An isolated neutrophilic duct injury can occur in peritumoral or obstructive pancreatitis. Drug-induced pancreatitis in patients with inflammatory bowel disease often mimics type 2 AIP clinically and pathologically. IL-8 and PD-L1 are potential ancillary immunohistochemical markers for type 2 AIP, requiring validation studies.

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.

Extra-pancreatic manifestations reported in association with pancreatitis; an international survey report

BACKGROUND/OBJECTIVES

Local and systemic manifestations have been reported in association with pancreatitis, anecdotally. However, a systematic collection on the prevalence of each of these symptoms in pancreatitis is lacking. We aimed to determine the prevalence of symptoms and diagnoses reported by a cohort of patients with pancreatitis, refer to as "extra pancreatic manifestation of pancreatitis".

METHODS

Cross-sectional study approved by the IRB and administered through a REDCap survey by "Mission: Cure", a nonprofit organization.

RESULTS

Of the 225 respondents analyzed; 89% were adults, 69% females, 89% Caucasians with 74% residing in the USA. 42% of children and 50% of adults reported exocrine pancreatic insufficiency while 8% of children and 26% of adults reported DM. Type 3c DM was reported in all children and 45% of adult DM cases. Children were diagnosed with genetic or hereditary pancreatitis more frequently compared to adults (33.3% versus 8%; p = <0.001). Significantly more symptoms and diagnoses were reported by adults when compared to children including nighttime sweats, bloating, or cramping, greasy or oily stools, feeling cold and GERD with p values of 0.002, 0.006, 0.046, 0.002 and 0.003 respectively.

CONCLUSIONS

Adults with pancreatitis frequently report symptoms not known to be associated with pancreatitis. Studies investigating mechanisms for these associated symptoms should be explored.

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.