Review article: autoimmune pancreatitis - management of an emerging disease

Diagnostic Utility of Serum IgG4 in Autoimmune Pancreatitis: An Updated Comprehensive Systematic Review and Meta-analysis

OBJECTIVES

Despite many studies suggesting an association between serum immunoglobulin G4 (sIgG4) and autoimmune pancreatitis (AIP), the evidence of utility in differentiation between AIP and pancreatic cancer (PC) remain uncertain.

METHODS

The analysis based on published studies. Data were pooled by means of a random-effects model, and sensitivity, specificity, diagnostic odds ratios (DOR), areas under summary receiver operating characteristic curves were calculated.

RESULTS

In the included thirteen studies, sIgG4 were measured in 594 patients with AIP and 958 patients with PC. The pooled sensitivity, specificity, DOR, and area under the curve were 0.72 [95% confidence interval (CI): 0.68-0.75], 0.93 (95% CI: 0.92-0.95), 51.37 (95% CI: 23.20-113.74), and 0.91 (95% CI: 0.87-0.95). Subgroup analyses of the DORs for region and year: Asia, (112.10; 95% CI: 27.72-453.32), non-Asia (26.01; 95% CI: 12.38-54.65), and year before 2011 (107.61; 95% CI: 39.30-294.68), year after 2011 (26.96; 95% CI: 9.78-74.32). Overall, sIgG4 was associated with AIP, the result revealed a moderate sensitivity 0.72 and high specificity 0.93. In the meta-analysis, the pooled DOR of sIgG4 levels of 2-fold upper limit 50.44 was similar with the DOR 51.37 when 1-fold cut-off value, but the summary receiver operating characteristic was 0.755 and 0.91. The higher specificity (from 93% to 98%) derived from the cut-off value (from 130-140 to 260-280 mg/dL) for sIgG4 occurred at a significant reduction in sensitivity (from 72% to 43%).

CONCLUSIONS

The study revealed sIgG4 is a good marker of AIP. Screening of sIgG4 may help clinicians differentiate between AIP and PC, and the best cut-off value should be 140 rather than 280 mg/dL.

Determination of the duration of glucocorticoid therapy in type 1 autoimmune pancreatitis: A systematic review and meta-analysis

BACKGROUND

The indications for maintenance glucocorticoid therapy (MGT) and its duration after initial remission of type 1 autoimmune pancreatitis (AIP) remain controversial. In contrast to the Japanese treatment protocol, the Mayo protocol does not recommend MGT after initial remission. This study aimed to evaluate the relapse rate in patients with type 1 AIP according to the duration of glucocorticoid therapy.

METHODS

We conducted a systematic literature review up until November 30, 2020, and identified 40 studies reporting AIP relapse rates. The pooled relapse rates were compared between groups according to the protocol and duration of glucocorticoids (routine vs. no MGT; glucocorticoids ≤6 months vs. 6-12 months vs. 12-36 months vs. ≥ 36 months). The pooled rates of adverse events related to glucocorticoids were also evaluated.

RESULTS

Meta-analysis indicated calculated pooled relapse rates of 46.6% (95% confidence interval (CI), 38.9-54.3%) with glucocorticoids for ≤ 6 months, 44.3% (95% CI, 38.8-49.8%) for 6-12 months, 34.1% (95% CI, 28.6-39.7%) for 12-36 months, and 27.0% (95% CI, 23.4-30.6%) for ≥ 36 months. The rate of relapse was also significantly lower in patients with routine-use protocol of MGT (31.2%; 95% CI, 27.5-34.8%) than in patients with no MGT protocol (44.1%; 95% CI, 35.8-52.4%). Adverse events were comparable between groups.

CONCLUSIONS

The rate of relapse tended to decrease with extended durations of glucocorticoid therapy up to 36 months. Clinicians may decide the duration of glucocorticoids according to patient condition, including comorbidities and risk of relapse.

Relapse predictors and serologically unstable condition of IgG4-related disease: a large Chinese cohort

OBJECTIVES

Patients with IgG4-related disease (IgG4-RD) typically respond well to initial glucocorticoid therapy, but always relapse with tapered or maintenance dosage of steroid. We aimed to identify the risk factors for relapse of IgG4-RD and explore the impact of active intervention on the serologically unstable condition.

METHODS

We performed a retrospective study of 277 IgG4-RD patients at Peking University People's Hospital from February 2012 through February 2019. They were all followed for >4 months. The primary outcome was patient relapse. Data on recurrence of IgG4-RD symptoms, laboratory and image findings were recorded, along with information on treatment in the serologically unstable condition.

RESULTS

The cumulative relapse rate was 12.86%, 27.84% and 36.1% at 12, 24 and 36 months, respectively. Younger age at onset, younger age at diagnosis, longer time from diagnosis to treatment and history of allergy were associated with relapse. Identified independent risk factors were longer time from diagnosis to treatment and history of allergy. When serum IgG4 level was 20%, 50% or 100% higher than that of the remission period, similar percentages of patients finally relapsed, regardless of whether they were in the immunosuppression intensified or non-intensified group. Median duration from serum IgG4 level instability to relapse in the intensified and non-intensified group was not statistically different.

CONCLUSION

The risk factors of relapse were longer time from diagnosis to treatment and history of allergy. Intervention in the serologically unstable condition was not helpful for reducing relapse rate.

British Society of Gastroenterology and UK-PSC guidelines for the diagnosis and management of primary sclerosing cholangitis

These guidelines on the management of primary sclerosing cholangitis (PSC) were commissioned by the British Society of Gastroenterology liver section. The guideline writing committee included medical representatives from hepatology and gastroenterology groups as well as patient representatives from PSC Support. The guidelines aim to support general physicians, gastroenterologists and surgeons in managing adults with PSC or those presenting with similar cholangiopathies which may mimic PSC, such as IgG4 sclerosing cholangitis. It also acts as a reference for patients with PSC to help them understand their own management. Quality of evidence is presented using the AGREE II format. Guidance is meant to be used as a reference rather than for rigid protocol-based care as we understand that management of patients often requires individual patient-centred considerations.

Serum Immunoglobulin G4 in Discriminating Autoimmune Pancreatitis From Pancreatic Cancer: A Diagnostic Meta-analysis

OBJECTIVE

Differentiation between autoimmune pancreatitis (AIP) and pancreatic cancer (PC) is a clinical challenge. Emerging published data on the accuracy of serum immunoglobulin G4 (IgG4) for the differential diagnosis between AIP and PC are inconsistent. The objective of our study was to perform a meta-analysis evaluating the clinical utility of serum IgG4 in the differential diagnosis between AIP and PC.

METHODS

We performed a systematic literature search of multiple electronic databases. The methodological quality of each study was assessed according to the Quality Assessment of Diagnostic Accuracy Studies checklist. Random-effects model was used to summarize the diagnostic odds ratio and other measures of accuracy.

RESULTS

Eleven studies comprising 523 AIP patients and 771 PC patients were included in the meta-analysis. The summary estimates for serum IgG4 in distinguishing AIP from PC were as follows: diagnostic odds ratio, 57.30 (95% confidence interval [CI], 23.17-141.67); sensitivity, 0.72 (95% CI, 0.68-0.76); specificity, 0.93 (95% CI, 0.91-0.94). The area under the curve of serum IgG4 in distinguishing AIP from PC was 0.9200.

CONCLUSIONS

Our meta-analysis found that serum IgG4 has high specificity and relatively low sensitivity in the differential diagnosis between AIP and PC. Therefore, serum IgG4 is useful in distinguishing AIP from PC.

Azathioprine Maintenance Therapy to Prevent Relapses in Autoimmune Pancreatitis

OBJECTIVES

Steroids are used to induce remission in autoimmune pancreatitis (AIP). Low-dosage steroid therapy or immunosuppressant (IMs) has been proposed as maintenance therapy to prevent AIP relapse. Few and conflicting data have been published on the efficacy of azathioprine (AZA) in preventing AIP relapse. The aim of this study was to evaluate the indication and efficacy of AZA as maintenance therapy to prevent disease relapse in AIP.

METHODS

Patients suffering from AIP diagnosed according to the ICDC in type 1, type 2, and not otherwise specified (NOS) were divided in those treated with AZA (AZA⁺ group) as maintenance therapy and not treated with maintenance therapy (AZA^- group). Exclusion criteria were: previous pancreatic surgery, other autoimmune diseases as indication for AZA treatment, and use of IMs different from AZA. Drug safety, clinical and instrumental outcome of AZA⁺ patients were evaluated.

RESULTS

A total of 23 patients (18 Males and 5 Females, mean age 54±11 years) in AZA⁺ group and 97 (58 Males and 39 Females, mean age 45±18 years) in AZA^- group were compared. In AZA⁺ group, patients were significantly older (P=0.043), type 1 AIP was more frequently diagnosed (87 vs. 51%, P=0.006), sIgG4 higher (758±625 vs. 311±409 mg/dl, P<0.001), other organ involvement (OOI) more frequently observed (83 vs. 48%, P=0.002), with higher frequency of relapse before AZA treatment (78 vs. 14%, P<0.001). Three patients in AZA⁺ group required drug discontinuation because of adverse events. Twenty patients were therefore evaluated for outcome. Six out of 20 patients (30%) relapsed after 24±15 months (5 in pancreas and 1 on biliary tract). They were retreated with steroids and continued AZA. Two out of 6 patients (33%) had a second relapse,after respectively 11 months (in pancreas and kidney) and 22 months (in kidney).

CONCLUSIONS

AZA is an effective and safe treatment to prevent AIP relapses.

Autoimmune Pancreatitis - A Riddle Wrapped in an Enigma

Autoimmune pancreatitis (AIP) was recognized as a clinical entity, at least in the West little more than 10 years ago. Since then, studies globally, and international collaboration, have led to important advances in our understanding of its clinical features, disease course, and management, although the aetiopathogenesis of this curious disease remains to be fully elucidated. Types 1 and 2 AIP have been described, of which type 1 is the commonest form, and best defined. International consensus now recognizes it as one of the many clinical manifestations of IgG4-related disease, and is now termed IgG4-related pancreatitis (IgG4-RP). The disease is not confined to a particular race, gender, or age, but often presents after the fifth decade in men. A common presentation is with jaundice due to low bile duct obstruction related to diffuse pancreatic enlargement (historically often leading to a misdiagnosis of cancer). Acute pancreatitis is unusual. Other organ involvement is a particular feature, including biliary disease, retroperitoneal fibrosis, generalized lymphadenopathy, renal, and lung involvement. No single test makes the diagnosis, and diagnostic criteria for type 1 AIP/IgG4-RP, which incorporate clinical, laboratory, radiological, pathological, and therapeutic parameters should be applied. A particular attempt should be made to make a histological diagnosis, which is characterized by an IgG4-positive lymphoplasmacytic infiltrate. Management is not based on randomized studies, but corticosteroids are the mainstay of treatment, providing rapid clinical and radiological benefit. However, clinical relapse is common (particularly in type 1 AIP, and in those with associated other organ involvement). Additional immunosuppression may be required, including azathioprine, and rituximab may play an emerging role. The disease course is variable, but loss of organ function (especially pancreatic exocrine failure and pancreatic atrophy) may occur.

The importance of IgG4 in the predictive model of thyroiditis

Immunoglobulin (Ig)G4-related sclerosing disease (IgG4-RSD) is a new disease entity first proposed with regard to autoimmune pancreatitis. A 67-year-old male patient was examined because of weight loss and an abdominal pain. Based on the clinical characteristics, laboratory parameters and ultrasound features, we identified the diagnosis of the IgG4-related systemic disease (IgG4-RSD), that was confirmed by the histopathological analysis after the biopsy of the head of pancreas. After confirmation, we started with the corticosteroid therapy with a good clinical, biochemical and morphological response. During the previous therapy, the disturbance of glucoregulation appeared, so we had to change the modality of treatment. We decided to add Azathioprine to the therapy in a dose of 150 mg/day. We achieved a stable phase of the disease with IgG 4.37 g/l and IgG4 0.179 g/l, and with no side effects from the therapy.

Biliary and hepatic involvement in IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD) is a multi-systemic disorder. IgG4-related sclerosing cholangitis (IgG4-SC) is the biliary manifestation of the disease, often in association with autoimmune pancreatitis (AIP). Hepatic manifestations of IgG4-RD are less well described within the literature.

AIM

To examine and present an overview of IgG4-RD with a focus on the biliary and hepatic manifestations.

METHODS

An electronic search using Medline was performed. Search items included 'IgG4 multi-system disease, IgG4 associated cholangitis, IgG4 associated liver disease and autoimmune pancreatitis (AIP)'.

RESULTS

IgG4-RD is characterised by an IgG4-positive lymphoplasmacytic tissue infiltrate, storiform fibrosis and an obliterative phlebitis. The HISORt criteria may be used to establish the diagnosis and incorporate a multi-disciplinary approach involving histology, radiology, serum IgG4 levels and response to steroid therapy. IgG4-SC is the commonest extrapancreatic manifestation of type-1 AIP, while the hepatic manifestations remain poorly defined. Important differential diagnoses include primary sclerosing cholangitis, secondary sclerosing cholangitis, cholangiocarcinoma and pancreatic carcinoma. Current treatment regimens remain ill defined although steroid therapy is used first line unless contraindicated. Patients with relapsing disease or multifocal disease should be considered for azathioprine. Available data would also suggest a role for rituximab.

CONCLUSIONS

IgG4-related sclerosing cholangitis is a common manifestation of IgG4-related disease which requires a multi-disciplinary approach to establish the diagnosis. Differentiating IgG4-related sclerosing cholangitis from other conditions, both benign and malignant, is challenging, but vital. Steroids remain the mainstay of treatment. Our understanding of the pathogenesis of the hepatic manifestations of IgG4-related disease continues to evolve.

Type 1 autoimmune pancreatitis and IgG4-related sclerosing cholangitis is associated with extrapancreatic organ failure, malignancy, and mortality in a prospective UK cohort

OBJECTIVES

Type I autoimmune pancreatitis (AIP) and IgG4-related sclerosing cholangitis (IgG4-related SC) are now recognized as components of a multisystem IgG4-related disease (IgG4-RD). We aimed to define the clinical course and long-term outcomes in patients with AIP/IgG4-SC recruited from two large UK tertiary referral centers.

METHODS

Data were collected from 115 patients identified between 2004 and 2013, and all were followed up prospectively from diagnosis for a median of 33 months (range 1-107), and evaluated for response to therapy, the development of multiorgan involvement, and malignancy. Comparisons were made with national UK statistics.

RESULTS

Although there was an initial response to steroids in 97%, relapse occurred in 50% of patients. IgG4-SC was an important predictor of relapse (P<0.01). Malignancy occurred in 11% shortly before or after the diagnosis of IgG4-RD, including three hepatopancreaticobiliary cancers. The risk of any cancer at diagnosis or during follow-up when compared with matched national statistics was increased (odds ratio=2.25, CI=1.12-3.94, P=0.02). Organ dysfunction occurred within the pancreas, liver, kidney, lung, and brain. Mortality occurred in 10% of patients during follow-up. The risk of death was increased compared with matched national statistics (odds ratio=2.07, CI=1.07-3.55, P=0.02).

CONCLUSIONS

Our findings suggest that AIP and IgG4-SC are associated with significant morbidity and mortality owing to extrapancreatic organ failure and malignancy. Detailed clinical evaluation for evidence of organ dysfunction and associated malignancy is required both at first presentation and during long-term follow-up.

Diagnostic utility of single-user peroral cholangioscopy in sclerosing cholangitis

OBJECTIVE

To evaluate the diagnostic utility of single-operator peroral cholangioscopy (SOC) in patients with sclerosing cholangitis.

METHODS

All patients with sclerosing cholangitis who underwent SOC procedures due to suspicious biliary strictures, in one Swedish and four UK tertiary centers in 2008-2012, were retrospectively enrolled. For each SOC procedure in sclerosing cholangitis, another one attempted due to a single biliary stricture in the same center and calendar year was randomly selected as control. Patients were followed up until death or last clinic visit until November 2012.

RESULTS

Fifty-four SOC procedures were attempted in 52 sclerosing cholangitis patients (48 with primary sclerosing cholangitis, 4 with IgG4-related sclerosing cholangitis). Cannulation with the SOC system failed more frequently in sclerosing cholangitis (15% vs. 2% in controls; p = 0.015). The sensitivity, specificity, and accuracy of SOC (including tissue sampling) for cancer diagnosis were similar in sclerosing cholangitis and controls (50% vs. 55%, 100% vs. 97%, and 88% vs. 80%, respectively) with largely overlapping confidence intervals. Adverse events were more common in sclerosing cholangitis, due to an increased frequency of cholangitis (11% vs. 2% in controls; p = 0.051).

CONCLUSIONS

SOC is equally accurate in cancer diagnosis in sclerosing cholangitis and patients with single biliary strictures. However, cholangioscope insertion may be hampered by bile duct narrowing and post-SOC cholangitis is more common in sclerosing cholangitis.

Review of the diagnosis, classification and management of autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a rare form of chronic pancreatitis, with as yet undetermined incidence and prevalence in the general population. Our understanding of it continues to evolve. In the last few years, 2 separate subtypes have been identified: type 1 AIP has been recognised as the pancreatic manifestation of a multiorgan disease, named immunoglobulin G4 (IgG4)-related disease while type 2 AIP is a pancreas specific disorder not associated with IgG4. International criteria for the diagnosis of AIP have been defined: the HISORt criteria from the Mayo clinic, the Japan consensus criteria and, most recently, the international association of pancreatology “International Consensus Diagnostic Criteria”. Despite this, in clinical practice it can still be very difficult to confirm the diagnosis and differentiate AIP from a pancreatic cancer. There are no large studies into the long-term prognosis and management of relapses of AIP, and there is even less information at present regarding the Type 2 AIP subtype. Further studies are necessary to clarify the pathogenesis, treatment and long-term outcomes of this disease. Critically for clinicians, making the correct diagnosis and differentiating the disease from pancreatic cancer is of the utmost importance and the greatest challenge.

Autoimmune pancreatitis: role of endoscopy in diagnosis and treatment

This review addresses the role of endoscopy in the diagnosis and treatment of autoimmune pancreatitis (AIP) and provides a diagnostic process for patients with suspected AIP. When should AIP be suspected? When can it be diagnosed without endoscopic examination? Which endoscopic approaches are appropriate in suspected AIP, and when? What are the roles of diagnostic endoscopic retrograde pancreatography, endoscopic biopsies, and IgG4 immunostaining? What is the proper use of the steroid trial in the diagnosis of AIP in patients with indeterminate computed tomography imaging? Should biliary stenting be performed in patients with AIP with obstructive jaundice?

IgG4-related disease

The term "IgG4-related disease" encompasses several disorders described many years ago under various designations depending on the organ or system involved (e.g., Mikulicz syndrome, Riedel's thyroiditis, and retroperitoneal fibrosis). The clinical presentation varies widely, as one or more organs may be affected, usually in the same region of the body and either synchronously or metachronously. The main targets are the pancreas, bile ducts, salivary glands, lachrymal glands, mediastinal lymph nodes, and retroperitoneum. IgG4-related disease is rare, with an estimated incidence of 0.2 to 1/100,000 in Japan and no available incidence data in occidental countries. Men older than 50 years are predominantly affected. Serum IgG4 levels are often greater than 1.35 g/L. Enlargement of the involved organs, which may be pseudotumoral, is due to a combination of infiltration by T cells and IgG4-expressing plasma cells, storiform fibrosis, and obliterative thrombophlebitis. Glucocorticoid therapy is effective but may be followed by relapses requiring the use of immunomodulating agents such as azathioprine, methotrexate and, more recently, rituximab. IgG4-related disease is not an autoimmune condition related to IgG4 autoantibodies, and neither does it involve immune complexes. Specific joint involvement has been reported in a very small number of patients.

Autoimmune pancreatitis: an illustrated guide to diagnosis

Autoimmune pancreatitis (AIP) remains one of the rarer forms of pancreatitis but has become increasingly well recognized and widely diagnosed as it is an important differential, particularly due to the dramatic response to appropriate therapy. It is now best considered as part of a multisystem disease and the notion of "IgG4-related systemic sclerosing disease" has become widely recognized as the number of extra-pancreatic associations of AIP grows. More recently AIP has been classified into two subtypes: lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct-centric pancreatitis (IDCP) with distinct geographical, age and sex distributions for the two subtypes, in addition to different pathological characteristics. The role of imaging is crucial in AIP and should be considered in conjunction with clinical, serological, and histopathological findings to make the diagnosis. Radiologists are uniquely placed to raise the possibility of AIP and aid the exclusion of significant differentials to allow the initiation of appropriate management and avoidance of unnecessary intervention. Radiological investigation may reveal a number of characteristic imaging findings in AIP but appearances can vary considerably and the focal form of AIP may appear as a pancreatic mass, imitating pancreatic carcinoma. This review will illustrate typical and atypical appearances of AIP on all imaging modes. Emphasis will be placed on the imaging features that are likely to prove useful in discriminating AIP from other causes prior to histopathological confirmation. In addition, examples of relevant differential diagnoses are discussed and illustrated.

Lymphotoxin β receptor signaling promotes development of autoimmune pancreatitis

BACKGROUND & AIMS

Little is known about the pathogenic mechanisms of autoimmune pancreatitis (AIP), an increasingly recognized, immune-mediated form of chronic pancreatitis. Current treatment options are limited and disease relapse is frequent. We investigated factors that contribute to the development of AIP and new therapeutic strategies.

METHODS

We used quantitative polymerase chain reaction, immunohistochemical, and enzyme-linked immunosorbent analyses to measure the expression of cytokines and chemokines in tissue and serum samples from patients with and without AIP. We created a mouse model of human AIP by overexpressing lymphotoxin (LT)α and β specifically in acinar cells (Ela1-LTab mice).

RESULTS

Messenger RNA levels of LTα and β were increased in pancreatic tissues from patients with AIP, compared with controls, and expression of chemokines (CXCL13, CCL19, CCL21, CCL1, and B-cell-activating factor) was increased in pancreatic and serum samples from patients. Up-regulation of these factors was not affected by corticosteroid treatment. Acinar-specific overexpression of LTαβ (Ela1-LTαβ) in mice led to an autoimmune disorder with various features of AIP. Chronic inflammation developed only in the pancreas but was sufficient to cause systemic autoimmunity. Acinar-specific overexpression of LTαβ did not cause autoimmunity in mice without lymphocytes (Ela1-LTab/Rag1(-/-)); moreover, lack of proinflammatory monocytes (Ela1-LTab/Ccr2(-/-)) failed to prevent AIP but prevented early pancreatic tissue damage. Administration of corticosteroids reduced pancreatitis but did not affect production of autoantibodies, such as antipancreatic secretory trypsin inhibitor in Ela1-LTab mice. In contrast, inhibition of LTβR signaling reduced chemokine expression, renal immune-complex deposition, and features of AIP in Ela1-LTab mice.

CONCLUSIONS

Overexpression of LTαβ specifically in acinar cells of mice causes features of AIP. Reagents that neutralize LTβR ligands might be used to treat patients with AIP.

Chronic pancreatitis in dogs

Chronic pancreatitis used to be considered uncommon in dogs, but recent pathological and clinical studies have confirmed that it is in fact a common and clinically significant disease. Clinical signs can vary from low-grade recurrent gastrointestinal signs to acute exacerbations that are indistinguishable from classical acute pancreatitis. Chronic pancreatitis is a significant cause of chronic pain in dogs, which must not be underestimated. It also results in progressive impairment of endocrine and exocrine function and the eventual development of diabetes mellitus or exocrine pancreatic insufficiency or both in some affected dogs at end stage. The etiology is unknown in most cases. Chronic pancreatitis shows an increased prevalence in certain breeds, and recent work in English Cocker Spaniels suggests it is part of a polysystemic immune-mediated disease in this breed. The histological and clinical appearance is different in different breeds, suggesting that etiologies may also be different. Diagnosis is challenging because the sensitivities of the available noninvasive tests are relatively low. However, with an increased index of suspicion, clinicians will recognize more cases that will allow them to institute supportive treatment to improve the quality of life of the patient.

Diagnostic Dilemma in a Patient with Jaundice: How to Differentiate between Autoimmune Pancreatitis, Primary Sclerosing Cholangitis and Pancreas Carcinoma

A 68-year-old male patient was referred to our institution in May 2011 for a suspected tumor in the pancreatic head with consecutive jaundice. Using magnetic resonance imaging, further differentiation between chronic inflammation and a malignant process was not possible with certainty. Apart from cholestasis, laboratory studies showed increased values for CA 19-9 to 532 U/ml (normal <37 U/ml) and hypergammaglobulinemia (immunoglobulin G, IgG) of 19.3% (normal 8.0–15.8%) with an elevation of the IgG4 subtype to 2,350 mg/l (normal 52–1,250 mg/l). Endoscopic retrograde cholangiopancreatography revealed a prominent stenosis of the distal ductus hepaticus communis caused by pancreatic head swelling and also a bihilar stenosis of the main hepatic bile ducts. Cytology demonstrated inflammatory cells without evidence of malignancy. Under suspicion of autoimmune pancreatitis with IgG4-associated cholangitis, immunosuppressive therapy with steroids and azathioprine was started. Follow-up endoscopic retrograde cholangiopancreatography after 3 months displayed regressive development of the diverse stenoses. Jaundice had disappeared and blood values had returned to normal ranges. Moreover, no tumor of the pancreatic head was present in the magnetic resonance control images. Due to clinical and radiological similarities but a consecutive completely different prognosis and therapy, it is of fundamental importance to differentiate between pancreatic cancer and autoimmune pancreatitis. Especially, determination of serum IgG4 levels and associated bile duct lesions induced by inflammation should clarify the diagnosis of autoimmune pancreatitis and legitimate immunosuppressive therapy.

Immunoglobulin subclass 4 for the diagnosis of immunoglobulin subclass 4-associated diseases in an unselected liver and pancreas clinic population

AIMS

  The diagnosis of autoimmune pancreatitis (AIP) and immunoglobulin subclass 4 (IgG(4) )-associated cholangitis (IAC) is based on imaging studies, serology, histology and a response to steroid therapy. The major serological finding is an elevation of the serum IgG(4) concentration. Previous studies have shown that its sensitivity is about 70% and its specificity exceeds 90% at a cut-off of 140 mg/dl in selected patient populations. The aim of the present study was to assess the performance of serum IgG(4) as a diagnostic parameter in an unselected liver and pancreas clinic population.

METHODS AND RESULTS

  IgG(4) was prospectively determined in 1412 patients and clinical diagnoses were recorded from a review of patient charts. The prevalence of AIP or IAC in the entire cohort was 1.1% (n= 15). The sensitivity of IgG(4) for the diagnosis of AIP and IAC was 80% and the specificity was 86% at a cut-off value of ≥135 mg/dl. The positive predictive value and the negative predictive value were 6% and 99.7%, respectively. The most common differential diagnosis in patients with elevated IgG(4) was liver cirrhosis.

CONCLUSION

  IgG(4) has a reasonable sensitivity and specificity in a liver and pancreas clinic population, where liver cirrhosis appears to be the most frequent differential diagnosis for elevated IgG(4) concentrations.