Lymphoplasmacytic Sclerosing Pancreatitis Research Articles

Role of Endoscopic Ultrasonography-Guided Fine Needle Aspiration/Biopsy in the Diagnosis of Autoimmune Pancreatitis

Type 1 autoimmune pancreatitis (AIP) is histologically characterized by lymphoplasmacytic sclerosing pancreatitis (LPSP). Recently, the diagnostic yield of endoscopic ultrasonography-guided fine needle aspiration/biopsy (EUS-FNA/B) for AIP has been reported. However, its role in the diagnostic flow of AIP is not fully elucidated. We retrospectively reviewed 53 consecutive patients who were suspected with AIP and underwent EUS-FNA/B. We evaluated the contribution of EUS-FNA/B to the diagnosis of AIP before considering response to steroid therapy among patients with diffuse enlargement of the pancreas and those with focal enlargement, respectively. Twenty-two patients showed diffuse pancreatic enlargement and 31 showed focal enlargement. The final diagnosis was definitive AIP in 32 patients, probable AIP in 2, possible AIP in 1, and mass-forming focal pancreatitis in 18. There was no change in diagnosis after EUS-FNA/B among patients with diffuse pancreatic enlargement, while diagnosis changed in 38.7% (12/31) among those with focal enlargement—there was a probable to definitive diagnosis in 4 patients, unspecified to definitive in 3, and unspecified to probable in 5. EUS-FNB provided a significantly higher sensitivity for typical pathological findings of LPSP than EUS-FNA, and 10 patients were diagnosed as pathologically definitive AIP by EUS-FNB, though none were by EUS-FNA (p = 0.002). EUS-FNA/B was useful in the diagnosis of focal type AIP, and steroid therapy could be introduced after the diagnosis was confirmed. Meanwhile, EUS-FNA/B provided no contribution to diagnosis of diffuse type AIP. EUS-FNB showed a higher diagnostic yield than FNA.

Comparison of a 22-gauge Franseen-tip needle with a 20-gauge forward-bevel needle for the diagnosis of type 1 autoimmune pancreatitis: a prospective, randomized, controlled, multicenter study (COMPAS study)

Histologic diagnosis of autoimmune pancreatitis (AIP) using EUS-guided FNA (EUS-FNA) is difficult. To address this issue, new fine-needle biopsy (FNB) needles were recently developed. Here, we prospectively evaluated 2 newly designed EUS-FNB needles for histologic evaluation in patients with type 1 AIP. This was a prospective, randomized, multicenter trial comparing biopsy specimens obtained with a 22-gauge Franseen needle or a 20-gauge forward-bevel needle in patients with suspected type 1 AIP. AIP was diagnosed according to international consensus diagnostic criteria. The primary endpoint was the sensitivity of EUS-FNB needles, and secondary endpoints were the amount of specimen obtained, histology of the pancreas based on evaluation of lymphoplasmacytic sclerosing pancreatitis (LPSP), and contribution of histologic findings to the diagnosis of AIP. One hundred ten patients were randomly assigned to the Franseen group (22-gauge Franseen needle) or the forward-bevel group (20-gauge forward-bevel needle). EUS-FNB sampling was successful in all patients. Nine patients were excluded because of diagnoses other than AIP. Compared with the forward-bevel needle, the Franseen needle obtained a significantly greater number of high-power fields. Of 101 patients, 39 patients (78%) in the Franseen group and 23 patients (45%) in the Forward-bevel group were diagnosed with level 1 or 2 LPSP (P= .001). Thirty-six patients could not be diagnosed with type 1 AIP without EUS-FNB specimen results. The 22-gauge Franseen needle should be routinely used for histologic diagnosis of type 1 AIP. (Clinical trial registration number: UMIN 000027668.).

The role of EUS-guided fine needle aspiration in autoimmune pancreatitis: a single center prospective study

Objectives: Histopathological examination is pivotal in diagnosing autoimmune pancreatitis (AIP). The usefulness of EUS-guided fine needle aspiration (EUS-FNA) in diagnosing AIP remains controversial worldwide. The authors conducted this study to evaluate the efficacy of EUS-FNA for AIP diagnosis using a 22-gauge needle.Methods: Between January 2013 and May 2017, 37 patients had imaging studies suggestive of AIP at Tongji Hospital, and 27 patients of them were enrolled in this study. Tissue specimens acquired through EUS-FNA were analyzed for periductal lymphoplasmacytic infiltrate (LPI), storiform fibrosis (SF), obliterative phlebitis (OP) and immunoglobulin G4 (IgG4)-positive plasma cell counts. Clinical Trials.gov no: TJ-C20121220.Results: LPI and SF were present in 18 (66.67%) and 18 (66.67%) of 27 patients, respectively. Abundant IgG4-positive plasmacyte infiltration >10/high-power field (HPF) was detected in 8 of 27 patients (29.63%). OP and the characteristic findings of idiopathic duct-centric chronic pancreatitis (IDCP) and granulocytic epithelial lesion (GEL) were not detected in this study. According to the International Consensus Diagnostic Criteria (ICDC) for AIP, 5 and 12 of 27 patients were assessed as having level 1 and level 2 histological findings, respectively, suggesting that 17 of 27 patients (62.96%) had lymphoplasmacytic sclerosing pancreatitis (LPSP) based on the ICDC.Conclusions: In 92.6% of patients, pancreatic tissues with >5 HPFs were obtained by EUS-FNA using a 22-G needle. In 63% of patients, histology was evaluated to be ≥ level 2 according to the ICDC. The study indicates that EUS-FNA with a 22-G needle is valuable in the histopathological diagnosis of AIP.

Diagnosis of Autoimmune Pancreatitis: The Evolution of Diagnostic Criteria for a Rare Disease

Diagnosis of Autoimmune Pancreatitis: The Evolution of Diagnostic Criteria for a Rare Disease

From Pathogenesis, Clinical Manifestation, and Diagnosis to Treatment: An Overview on Autoimmune Pancreatitis.

Autoimmune pancreatitis (AIP) is a special type of chronic pancreatitis which is autoimmune mediated. The international consensus diagnostic criteria (ICDC) 2011 proposed two types of AIP: type I is associated with histological pattern of lymphoplasmacytic sclerosing pancreatitis (LPSP), characterized by serum IgG4 elevation, whereas type 2 is named idiopathic duct-centric pancreatitis (IDCP), with granulocytic epithelial lesion (GEL) and immunoglobulin G4 (IgG4) negative. The pathogenic mechanism is unclear now; based on genetic factors, disease specific or related antigens, innate and adaptive immunity may be involved. The most common clinical manifestations of AIP are obstructive jaundice and upper abdominal pain. The diagnosis can be made by a combination of parenchymal and ductal imaging, serum IgG4 concentrations, pancreatic histology, extrapancreatic disease, and glucocorticoid responsiveness according to ICDC 2011. Because of the clinical and imaging similarities with pancreatic cancer, general work-up should be done carefully to exclude pancreatic malignant tumor before empirical trial of glucocorticoid treatment. Glucocorticoid is the most common drug for AIP to induce remission, while there still exists controversy on steroid maintenance and treatment for relapse. Further studies should be done to identify more specific serum biomarkers for AIP, the pathogenic mechanisms, and the treatment for relapse.

Autoimmune pancreatitis.

Autoimmune pancreatitis (AIP) is a rare, distinct and increasingly recognized form of pancreatitis which has autoimmune features. The international consensus diagnostic criteria (ICDC) for AIP recently described two subtypes; type 1[lymphoplasmacytic sclerosing pancreatitis (LPSP)] and type 2 [idiopathic duct-centric pancreatitis (IDCP) or AIP with granulocytic epithelial lesion (GEL)]. Type 1 is the more common form of the disease worldwide and current understanding suggests that it is a pancreatic manifestation of immunoglobulin G4-related disease (IgG4-RD). In contrast, type 2 AIP is a pancreas-specific disease not associated with IgG4 and mostly without the overt extra-pancreatic organ involvement seen in type 1. The pathogenesis of AIP is not completely understood and its clinical presentation is non-specific. It shares overlapping features with more sinister pathologies such as cancer of the pancreas, which continues to pose a diagnostic challenge for clinicians. The diagnostic criteria requires a variable combination of histopathological, imaging and serological features in the presence of typical extrapancreatic lesions and a predictable response to steroids.

Comparison of neutrophil infiltration between type 1 and type 2 autoimmune pancreatitis

BackgroundCharacteristics of type 2 autoimmune pancreatitis (AIP) is granulocyte epithelial lesions, called idiopathic duct-centric pancreatitis (IDCP). To clarify pathogenesis of IDCP, we investigated mechanism of neutrophil infiltration in type 1 AIP, called lymphoplasmacytic sclerosing pancreatitis (LPSP) and IDCP. MethodThis study was performed on resected pancreata from patients with alcoholic chronic pancreatitis (ACP, n = 10), LPSP (n = 10) and IDCP (n = 12). The number of neutrophils around the pancreatic ducts was counted. The expression of neutrophils chemoattractants granulocyte chemotactic protein-2 (GCP-2) and interleukin-8 (IL-8) in the pancreatic duct epithelia was examined using immunohistochemistry. The cell staining intensity is scored as negative (0), weak (1), moderate (2) or strong (3). ResultsThe median number of neutrophils around the interlobular pancreatic ducts was significantly higher in IDCP (15.16; interquartile range [IQR]: 9.74–18.41) than in ACP (2.66; IQR: 1.33–4.33) (P < 0.05) and LPSP (3.16; IQR: 2.74–4.57) (P < 0.01). There was no significant difference in the median number of neutrophils around the intralobular pancreatic ducts among ACP (1.16; IQR: 0.33–3.41), LPSP (3.16; IQR: 0.74–5.5) and IDCP (3.00; IQR: 1.08–7.91). The median score of GCP-2 in the interlobular pancreatic duct epithelia was significantly higher in IDCP (1.5; IQR: 0.25–2) than in ACP (0; IQR: 0–0.75) (P < 0.05) and LPSP (0; IQR: 0–0.75) (P < 0.05). There was no significant difference in the median score of IL-8 in the interlobular pancreatic duct epithelia among ACP (0; IQR: 0–0.75), LPSP (1; IQR: 0–1.75) and IDCP (0.5; IQR: 0–1). ConclusionsSignificantly increased neutrophil infiltration around the interlobular pancreatic duct in IDCP may depend on GCP-2.

Multiple gene mutations in patients with type 2 autoimmune pancreatitis and its clinical features.

BackgroundIt is now clear that there are two histological types (type 1 and type 2) of autoimmune pancreatitis (AI P). The histological substance of type 1 AI P is known as lymphoplasmacytic sclerosing pancreatitis (LPSP) or traditional AIP, and type 2 AIP is characterized by distinct histology called idiopathic duct centric pancreatitis (IDCP). Serum IgG4 increase is considered as a marker for type 1 AI P. Far less is known about type 2 and it lacks predicting markers, so it easily leads to missed diagnosis and misdiagnosis.The aim of this studyThe aim of this study was to describe multi-gene mutations in patients with type 2 AI P and its clinical features.Material and methodsThree unrelated patients with type 2 AI P, 10 cases with type 1 AIP, 15 cases with other chronic pancreatitis and 120 healthy individuals were studied. The mutations and polymorphisms of 6 genes involved in chronic pancreatitis or pancreatic cancer — PRSS1, SPINK1, CFTR, MEN1, PKHD1, and mitochondrial DNA – were sequenced. Information of clinical data was collected by personal interview using a structured questionnaire.ResultsNovel mutations were found in the genes encoding for MEN1 (p.546 Ala > The) and PKHD1 (c. 233586 A > G and c. 316713 C > T) from patients with type 2 AIP. What is more, the serum TCR (T cell receptor) level is relatively higher in patients with type 2 AIP than in patients with type 1 AIP and other chronic pancreatitis or normal controls. Weight loss was the major manifestation and no patients had extrapancreatic involvement in type 2 AIP.ConclusionsType 2 AIP may occur with multi-gene mutations. For screening purposes, it is more reasonable to evaluate TCR levels in serum.

Histological evaluation of obliterative phlebitis for the diagnosis of autoimmune pancreatitis

Obliterative phlebitis is a useful pathological finding for the diagnosis of lymphoplasmacytic sclerosing pancreatitis (LPSP), or type 1 autoimmune pancreatitis. The present study evaluated histological findings of obliterative phlebitis, including the significance of adding Elastica van Gieson stain (EVG) in comparison with other pancreatic conditions. Specimens of LPSP (n=18), chronic pancreatitis (CP; n=24), and pancreatic ductal adenocarcinoma (PDA; n=45) were enrolled. Obliterative venous lesions (OVLs), defined as the presence of inflammatory cells and/or fibrosis inside the tunica adventitia, were counted and compared between hematoxylin and eosin stain (H&E) and EVG. OVLs were classified into three types: OVL-1, lymphoplasmacytic infiltration and fibrosis against a loose textured background; OVL-2, dense fibrosis with minimal or no lymphoplasmacytic infiltration; and OVL-3, densely packed lymphoplasmacytic infiltration without fibrosis. OVL type and OVL size were compared between disease groups. OVL counts in LPSP, CP, and PDA were significantly higher with EVG than with H&E (p<0.001). OVL-1 was most common in LPSP (H&E 92.4%, EVG 79.8%), and was identified in almost all cases of LPSP, but was less common in CP and PDA. Maximum diameter and OVL count in 1cm(2) of OVL-1 were high for LPSP. Maximum diameter of OVL-1 ≥150μm was observed in 17 LPSP, 0 CP, and 1 PDA cases (sensitivity 94.4%, specificity 98.6%). Additional EVG is useful for excluding conditions mimicking OVL-1 or detecting OVL in small specimens. The presence of OVL-1 with diameter ≥150μm is highly diagnostic for LPSP.

Autoimmune Pancreatitis-What is Known, What Needs to be Known

Autoimmune Pancreatitis (AIP) is an emerging clinical entity found in 4.6-6 percent of patients with chronic pancreatitis [1]. It was first reported as an idiopathic chronic pancreatitis associated with hypergammaglobulinemia by Sarles et al. [2], with the term AIP being first used by Yoshida et al. [3]. In 2003, Notohara and coworkers described two types of AIP: Lymphoplasmacytic Sclerosing Pancreatitis (LPSP) termed “type 1 AIP” and idiopathic duct-centric chronic pancreatitis with Granulocyte Epithelial Lesion (GEL) termed “type 2 AIP” [1] (Table 1).

A case of pancreatic ductal adenocarcinoma with marked infiltration with IgG4-positive cells

A 75-year-old man was diagnosed as having pancreatic ductal carcinoma containing remarkable lymphocytic and plasma cell infiltration, as revealed by the cytological examination of endoscopic ultrasound guided fine-needle aspiration (EUS-FNA) specimen. The EUS-FNA specimen showed small amounts of atypical epithelium with noticeable lymphocytes and plasma cells. A pancreatic resection was performed, and the histopathological features showed an invasive pancreatic ductal carcinoma with autoimmune pancreatitis (AIP) lymphoplasmacytic sclerosing pancreatitis (LPSP)-like lesions. Most of the plasma cells were immunoreactive to anti-IgG4 antibody. EUS-FNA may be necessary for the differential diagnosis of AIP and pancreatic cancer, and close attention should be given to the presence of marked lymphoplasmacytic cells in EUS-FNA specimens while making the diagnosis.

Differences between diffuse and focal autoimmune pancreatitis

To investigate differences in clinical features between diffuse- and focal-type autoimmune pancreatitis (AIP). Based on radiological findings by computed tomography and/or magnetic resonance imaging, we divided 67 AIP patients into diffuse type (D type) and focal type (F type). We further divided F type into head type (H type) and body and/or tail type (B/T type) according to the location of enlargement. Finally, we classified the 67 AIP patients into three groups: D type, H type and B/T type. We compared the three types of AIP in terms of clinical, laboratory, radiological, functional and histological findings and clinical course. There were 34 patients with D-type, 19 with H-type and 14 with B/T-type AIP. Although obstructive jaundice was frequently detected in D-type patients (88%) and H-type patients (68%), no B/T-type patients showed jaundice as an initial symptom (P < 0.001). There were no differences in frequency of abdominal pain, but acute pancreatitis was associated more frequently in B/T-type patients (36%) than in D-type patients (3%) (P = 0.017). Serum immunoglobulin G (IgG)4 levels were significantly higher in D-type patients (median 309 mg/dL) than in B/T-type patients (133.5 mg/dL) (P = 0.042). Serum amylase levels in B/T-type patients (median: 114 IU/L) were significantly greater than in H-type patients (72 IU/L) (P = 0.049). Lymphoplasmacytic sclerosing pancreatitis (LPSP) was histologically confirmed in 6 D-type, 7 H-type and 4 B/T-type patients; idiopathic duct-centric pancreatitis was observed in no patients. Marked fibrosis and abundant infiltration of CD20-positive B lymphocytes with few IgG4-positive plasma cells were detected in 2 B/T-type patients. Steroid therapy was effective in all 50 patients (31 D type, 13 H type and 6 B/T type). Although AIP relapsed during tapering or after stopping steroids in 3 D-type and 3 H-type patients, no patients relapsed in B/T type. During follow-up, radiological features of 6 B/T-type patients were not changed and 1 B/T-type patient improved naturally. Clinical features of H-type AIP were similar to those of D-type, but B/T-type differed from D and H types. B/T-type may involve diseases other than LPSP.

Autoimmune Pancreatitis with Histologically Proven Lymphoplasmacytic Sclerosing Pancreatitis with Granulocytic Epithelial Lesions

Recent histological and clinical studies have suggested the existence of 2 distinct types of autoimmune pancreatitis (AIP): type 1 AIP related to IgG4, exhibiting lymphoplasmacytic sclerosing pancreatitis (LPSP), and type 2 AIP related to granulocyte epithelial lesions (GELs), exhibiting idiopathic duct-centric chronic pancreatitis (IDCP). We herein present a case of type 1 AIP with histologically proven LPSP with GELs. This patient had neither serum IgG4 elevation nor MPD narrowing. In this case, the clinically and histologically atypical findings for type 1 AIP are intriguing.

Endoscopic ultrasound-guided fine needle aspiration in the differentiation of type 1 and type 2 autoimmune pancreatitis

To investigate the usefulness of endoscopic ultra-sound-guided fine needle aspiration (EUS-FNA) in the differentiation of autoimmune pancreatitis (AIP). We retrospectively reviewed 47 of 56 AIP patients who underwent EUS-FNA and met the Asian diagnostic criteria. On 47 EUS-FNA specimens, we evaluated the presence of adequate material and characteristic features of lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct-centric pancreatitis (IDCP) mentioned in the International Consensus Diagnostic Criteria and examined if these findings make a contribution to the differential diagnosis of type 1 and type 2 AIP. A disposable 22-gauge needle was used for EUS-FNA. Adequate specimens including pancreatic tissue for differentiating AIP from cancer were obtained from 43 of 47 patients who underwent EUS-FNA. EUS-FNA was performed from the pancreatic head in 21 cases, which is known to be technically difficult when performed by core biopsy; there was no significant difference in the results compared with pancreatic body-tail. Nine of 47 patients met level 1 findings of LPSP and 5 patients met level 2 findings of LPSP. No one met level 1 findings of IDCP, but 3 patients met level 2 findings of IDCP. Of 10 seronegative cases, 2 cases were diagnosed with "definitive type 1 AIP", and 3 cases were diagnosed with "probable type 2 AIP" when considering both the level 2 histological findings and response to steroids. EUS-FNA is useful in the differentiation of type 1 and type 2 AIP, particularly in seronegative cases.

Recent advances in autoimmune pancreatitis

It is now clear that are two histological types (Type-1 and Type-2) of autoimmune pancreatitis (AIP). The histological pattern of Type-1 AIP, or traditional AIP, is called lymphoplasmacytic sclerosing pancreatitis (LPSP). The histological pattern of Type-2 AIP is characterized by neutrophilic infiltration in the epithelium of the pancreatic duct. In general, Type-2 AIP patients are younger, may not have a male preponderance, and rarely show elevation of serum IgG4 compared with Type-1 AIP patients. Unlike Type-1 AIP patients, Type-2 AIP patients rarely have associated sclerosing diseases, but they are more likely to have acute pancreatitis and ulcerative colitis. Although Type-2 AIP is sometimes observed in the USA and Europe, most AIP cases in Japan and Korea are Type-1. The international consensus diagnostic criteria for AIP comprise 5 cardinal features, and combinations of one or more of these features provide the basis for diagnoses of both Type-1 and Type-2 AIP. Due to the fact that steroid therapy is clinically, morphologically, and serologically effective in AIP patients, it is the standard therapy for AIP. The indications for steroid therapy in AIP include symptoms such as obstructive jaundice and the presence of symptomatic extrapancreatic lesions. Oral prednisolone (0.6 mg/kg/day) is administered for 2–4 weeks and gradually tapered to a maintenance dose of 2.5–5 mg/day over a period of 2–3 months. Maintenance therapy by low-dose prednisolone is usually performed for 1–3 years to prevent relapse of AIP.

Pathologic Findings of Autoimmune Pancreatitis and IgG4-Related Disease

Autoimmune pancreatitis (AIP) is pathologically characterized by lymphoplasmacytic infiltration and fibrosis. However, AIP is not a single entity, but rather includes two histological types — lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct-centric chronic pancreatitis (IDCP) — of which the former constitutes the pancreatic manifestation of IgG4-related disease. The inflammation seen in peripancreatic adipose tissue and the interlobular area in LPSP, such as dense lymphoplasmacytic infiltration with fibrosis, storiform fibrosis, and obliterative phlebitis, is common among the various lesions that belong to IgG4-related disease. However, some lesions in the family of IgG4-related disease, such as IgG4-related sclerosing sialadenitis and lymphadenopathy, often lack prominent fibrosis, suggesting the histological variation of this entity. Nonetheless, histological features are important in the formation of a pathological diagnosis of IgG4-related disease because the presence of numerous IgG4-positive plasma cells is not necessarily specific to this disease.

History of Autoimmune Pancreatitis and Mikuliczs Disease

The concept of a new class of systemic disease, IgG4-related disease, was established from findings in patients with autoimmune pancreatitis and Mikuliczs disease, showing the involvement of other organs. Autoimmune pancreatitis presents as a swollen pancreas that mimics pancreatic cancer and was first recognized by its characteristic findings of lymphoplasmacytic sclerosing pancreatitis (LPSP) and irregular narrowing of the main pancreatic duct. It was later found to be associated with autoimmunity and with high serum IgG4 concentrations and IgG4-bearing plasma cell infiltration. Autoimmune pancreatitis is also characterized by the systemic distribution of extra-pancreatic lesions and shows similar pathological findings of IgG4-bearing plasma cell infiltration, suggesting that autoimmune pancreatitis is a systemic, IgG4-related disease. Mikuliczs disease is another type of IgG4-related disease, presenting as symmetrical, painless enlargement of the lacrimal and salivary glands. Mikuliczs disease was considered as a complex of symptoms, rather than a disease entity. Furthermore, this disease had been regarded as one manifestation of a more generalized symptom complex known as Sjogrens syndrome. Mikuliczs disease was later distinguished from Sjogrens syndrome by its high serum IgG4 concentration and several characteristic clinical features. Mikuliczs disease shows similar systemic organ involvements as autoimmune pancreatitis. At present, autoimmune pancreatitis and Mikuliczs disease are recognized as major constituents of IgG4-relatated disease. Keywords: Autoimmune pancreatitis, IgG4, IgG4-related disease, lymphoplasmacytic sclerosing pancreatitis, Mikulicz's disease, Sjogren's syndrome, Corticosteroid Treatment, Mikulicz's Syndrome

IgG4-Related Disease : A Novel Lymphoproliferative Disorder Discovered and Established in Japan in the 21st Century

IgG4-related disease is a novel lymphoproliferative disorder that shows hyper-IgG4-γ-globulinemia and IgG4-producing plasma cell expansion in affected organs with fibrotic or sclerotic changes. Patients show systemic inflammatory conditions and various symptoms depending on the affected organ. Since the first report of patients with elevated serum IgG4 in sclerosing pancreatitis in 2001, various systemic disorders described by many names have been reported. Despite similarities in the organs involved in IgG4-related Mikulicz's disease and Sjögren's syndrome, there are marked clinical and pathological differences between these conditions. Most patients diagnosed with autoimmune pancreatitis in Japan have IgG4-related pancreatitis [Type 1 autoimmune pancreatitis (AIP), lymphoplasmacytic sclerosing pancreatitis (LPSP)], a disease distinct from some of the western type [Type 2 AIP, idiopathic duct-centric chronic pancreatitis (IDCP), autoimmune pancreatitis with granulocytic epithelial lesions (GEL)]. Diagnosis of IgG4-related disease is characterized by both elevated serum IgG4 (>135 mg/dL) and histopathological features including lymphocyte and IgG4(+) plasma cell infiltration (IgG4(+) plasma cells/IgG(+) plasma cells>40%). Differential diagnosis from other distinct disorders, such as sarcoidosis, Castleman's disease, Wegener's granulomatosis, lymphoma, cancer, and other existing conditions associated with high serum IgG4 level or abundant IgG4-bearing plasma cells in tissues is necessary. We have begun a clinical prospective study to establish a treatment strategy (Phase II prospective treatment study for IgG4-multiorgan lymphoproliferative syndrome: UMIN R000002311).

Serum IgG4-negative autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is considered to be a pancreatic lesion of IgG4-related systemic disease, but about 20% of AIP patients do not have elevated serum IgG4 levels. This study aimed to clarify the pathophysiology of AIP patients without elevated serum IgG4 levels. Fifty-eight AIP patients were divided into 2 groups: those with elevated serum IgG4 levels (>135 mg/dl; SIgG4-positive AIP) and those without (SIgG4-negative AIP). The 2 groups' clinical, serological, radiological, and histological findings, as well as salivary and lacrimal gland function, were compared. Serum IgG4 levels were elevated in 45 AIP patients and normal in 13 patients. In SIgG4-negative AIP patients, the female ratio tended to be high; obstructive jaundice was less likely; abdominal pain and acute pancreatitis were more likely; segmental swelling of the pancreatic body and/or tail was more common; sclerosing extrapancreatic lesions, salivary and lacrimal gland dysfunction, and abundant infiltration of IgG4-positive plasma cells in the gastric mucosa were less likely; and conservative follow-up was sometimes implemented. Histological examination of the pancreas of SIgG4-negative AIP showed lymphoplasmacytic sclerosing pancreatitis (LPSP) rather confined to the pancreas (n = 4), inadequate material (n = 2), and pancreatic fibrosis showing infiltration of lymphocytes without infiltration of IgG4-positive cells or neutrophils (n = 2). Clinicopathological features of SIgG4-negative AIP differed from those of SIgG4-positive AIP. Some SIgG4-negative AIP cases are LPSP rather confined to the pancreas. SIgG4-negative AIP may include idiopathic duct-centric pancreatitis (IDCP) or sclerosing pancreatitis other than LPSP or IDCP, but further studies are needed to clarify this issue.

Histopathologic and Clinical Subtypes of Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) has been extensively reported from Japan, Europe, and the United States. Whereas the descriptions of AIP from Japan have predominantly been based on the presence of a distinct clinical phenotype, reports from Europe and the United States describe at least 2 histopathologic patterns in patients' condition currently diagnosed as AIP, viz, lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct centric pancreatitis (IDCP) or granulocyte epithelial lesion (GEL)-positive pancreatitis. Although the 2 entities share common histopathologic features (periductal lymphoplasmacytic infiltration and peculiar periductal fibrosis), expert pathologists can accurately distinguish them based on other unique histopathologic features. Clinically, the 2 entities have similar clinical presentation (obstructive jaundice/pancreatic mass and a dramatic response to steroids) but differ significantly in their demography, serological characteristics, other organ involvement, and disease relapse. While LPSP is associated with elevation in titers of nonspecific autoantibodies and serum IgG4 levels, IDCP does not have definitive serological autoimmune markers. All experts agreed that the clinical phenotypes associated with LPSP and IDCP should be nosologically distinguished; however, their terminology was debated. Whereas most experts agreed that the entities should be referred to as type 1 and type 2 AIP, respectively, others had concerns regarding use of the term "autoimmune" to describe IDCP.