Pathological features of IgG4-related sclerosing disease. Curr Opin Rheumatol. 2011;23:74-79. [PMID: 21124089 DOI: 10.1097/BOR.0b013e328341347b]

Multimodality pictorial review of IgG4-related disease in the abdomen and pelvis

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a systemic, immune-mediated disease that can affect multiple organs, including the orbits, salivary glands, thyroid gland, lungs, aorta, pancreas, bile ducts, lymph nodes, and retroperitoneum. While timely diagnosis is particularly important given the efficacy of glucocorticoid treatment for IgG4-RD, accurate recognition can prove a challenge given the overlap between the imaging features of this disease and other entities.

PURPOSE

After a review of the epidemiology, pathophysiology, and clinical considerations (including treatment) associated with IgG4-RD, this pictorial review will showcase the variable imaging manifestations of this disease in the abdomen and pelvis. Post-treatment imaging appearance of these entities will be reviewed and mimickers of this disease in the abdomen and pelvis will be presented.

CONCLUSION

The presence of mass-like soft tissue with radiographic characteristics of fibrosis affecting multiple organs should raise suspicion for IgG4-RD, although definite diagnosis can only be made with appropriate clinical, serological, and pathologic data.

Vasculitis Mimics and Other Related Conditions

The approach to diagnosis of primary systemic vasculitis can be challenging, often requiring consideration of important secondary causes of vasculitis and non-inflammatory mimics. An atypical pattern of vascular involvement and/or atypical features of primary vasculitis (eg, cytopenia, lymphadenopathy) should prompt a more thorough investigation into other diseases. Herein, we review selected mimics organized by the size of blood vessels typically affected.

Immunoglobulin G4-Related Sclerosing Cholangitis Revealed by 68Ga-FAPI PET/MR

ABSTRACT

A 60-year-old woman with surgically confirmed immunoglobulin G4-related sclerosing cholangitis underwent 18F-FDG PET/CT due to significantly elevated serum CA-19-9 level, which revealed a hypermetabolic lesion in the residual liver. 68Ga-FAPI PET/MR was performed to further evaluate whether the FDG-avid lesion is a malignant tumor. Astonishingly, diffuse intense radioactivity was revealed throughout the liver, suggesting involvement of active immunoglobulin G4-related sclerosing cholangitis, but nonfocal elevated 68Ga-FAPI accumulation in the FDG-avid lesion indicated postoperative change. From this case, we speculated that FAPI imaging could be used for evaluation of chronic liver disease because fibroblast activation protein has a profibrogenic role in chronic liver injury.

The eosinophilic esophagitis and IgG4-related disease involving the esophagus

The study of eosinophilic esophagitis has become a dynamic field with an evolving understanding of the pathogenesis, diagnosis, and treatment. Immunoglobulin G4 (IgG4)-related disease exhibits systemic involvement but very rarely involves the esophagus. The article presents a clinical case: the history of ulcer and stricture of the esophagus in a young man of 17 years. The patient was finally diagnosed with IgG4-related and eosinophilic esophagitis and showed a good response to corticosteroid therapy. We herein report a rare case of dysphagia associated with IgG4-related disease and eosinophilic. We presented a review of modern data on the relationship of eosinophilic esophagitis and pathological IgG4-response.

Recurrent Immunoglobulin G4-Related Disease Shown on 18F-FDG and 68Ga-FAPI PET/CT

A 21-year-old man had been diagnosed with immunoglobulin G4-related disease (IgG4-RD) for 5 years, and the disease recurred 1 month ago. F-FDG PET/CT revealed intense FDG activity in the pituitary stalk, submandibular gland, pleura, pericardium, pancreas, liver, prostate, and multiple lymph nodes, which were considered the involvements of IgG4-RD. Ga-FAPI PET/CT also showed intense Ga-FAPI uptake in the above FDG-avid lesions except the lymph node involvement. Additionally, involvement in the lacrimal glands was detected by Ga-FAPI. The positive findings of Ga-FAPI in the current case highlighted that Ga-FAPI may have value in the evaluation of IgG4-RD.

Fibroblast Activation Protein-Targeted PET/CT with 68Ga-FAPI for Imaging IgG4-Related Disease: Comparison to 18F-FDG PET/CT

IgG4-related disease (RD) is characterized by lymphoplasmacytic infiltration enriched in IgG4-positive plasma cells and variable degrees of fibrosis with a characteristic storiform pattern. Since fibrosis is an important feature of IgG4-RD, we performed a prospective cohort study to evaluate the performance of ⁶⁸Ga-fibroblast activation protein inhibitor (FAPI), a recently introduced PET agent targeting fibroblast activation protein, in IgG4-RD. Methods: Twenty-six patients with IgG4-RD were recruited. All patients underwent both ⁶⁸Ga-FAPI and ¹⁸F-FDG PET/CT. The positive rates of the PET/CT scans in the involved organs and the uptake values were compared. Results: In a total of 136 involved organs in the 26 patients, ⁶⁸Ga-FAPI PET/CT additionally detected 18 (13.2%) involved organs in 13 (50.0%) patients, compared with ¹⁸F-FDG PET/CT. ⁶⁸Ga-FAPI PET/CT had a higher positive rate than ¹⁸F-FDG PET/CT in detecting involvement in the pancreas, bile duct/liver, and lacrimal gland. ⁶⁸Ga-FAPI also demonstrated significantly higher uptake than ¹⁸F-FDG in the matched disease in the pancreas, bile duct/liver, and salivary gland (P < 0.01). However, lymph node involvement with flip-flop uptake of ¹⁸F-FDG did not accumulate ⁶⁸Ga-FAPI. Conclusion: ⁶⁸Ga-FAPI might be a promising imaging agent for the assessment of IgG4-RD.

IgG4-related pleural disease in a patient with a history of unknown origin acute pancreatitis: a case report and review of the literature

Immunoglobulin G4-related disease is a rare autoimmune systemic disease with the capability of involving every organ. The disease is microscopically defined by a diffuse tissular inflammation with an infiltration of IgG4 positive plasma cells in the affected organs. IgG4 disease has an increasing incidence in the last few years with a growing interest in its pathophysiology still misunderstood to date. Despite the growing recognition of this pathology, the literature still does not allow to propose a simple diagnostic algorithm. In this article, we present a case of a 56-year-old man with a history of unknown etiology acute pancreatitis and a unilateral pleural effusion.

Clinical and pathological features of patients with antineutrophil cytoplasmic antibody-associated vasculitides concomitant with IgG4-related disease

AIM

The characteristics and the pathogenesis of the concomitant antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) and immunoglobulin G4-related disease (IgG4-RD) have not been elucidated.

METHOD

We included 92 AAV patients with renal biopsy results. Among them, 10 patients met both AAV and IgG4-RD criteria (concomitant group). The IgG subclasses of myeloperoxidase (MPO)-ANCA in both serum and renal tissue were measured and complement activation components were detected in serum.

RESULTS

Patients in the concomitant group had both elevated serum IgG4 levels and positive MPO-ANCA. They had higher levels of eosinophil counts, serum globulin, IgG, IgE and C-reactive protein than patients in the AAV alone group. All 10 patients had glomerulonephritis with crescents and seven patients also had segmental necrosis of the glomerular capillary wall. Most of them also presented with storiform fibrosis and lymphoplasmacytic infiltration in renal interstitium with IgG4 positive plasma cells more than 10/high-power field. Eight patients achieved remission with improved renal function, the other two patients were on maintenance dialysis. The IgG4 subclass of MPO-ANCA was higher in the concomitant group than that in AAV alone group. A merge of IgG4 and MPO immunofluorescence was observed in parts of the mesangium of concomitant AAV and IgG4-RD patients. For complement components, Bb and mannose-binding lectin were elevated in serum of concomitant AAV and IgG4-RD patients.

CONCLUSION

We showed a new overlap syndrome of AAV and IgG4-RD, in which the IgG4 subclass of ANCA may be a pathogenic factor.

The Challenge of Autoimmune Pancreatitis: A Portrayal From the Pediatric Perspective

Autoimmune pancreatitis (AIP) is a rare disorder characterized by prompt clinical response to corticosteroids. Lost tolerance to a variety of pancreatic antigens and subsequent development of autoantibodies are presumably involved in the initiation of AIP. Even pediatric patients have been reported with features of AIP, and awareness of this disorder is increasing among different clinicians. The terms lymphoplasmacytic sclerosing pancreatitis and idiopathic duct-centric pancreatitis refer to the different histologic patterns of AIP, named type 1 and type 2, respectively. A combination of serologic, radiologic, and histologic investigations is needed to assess diagnosis of AIP and rule out neoplastic disorders. In addition, type 1 AIP can be distinguished by raised levels of serum immunoglobulin G4 and should be considered as part of systemic immunoglobulin G4-related disease. Conversely, type 2 AIP is frequently reported in younger patients and has less clear immune-mediated pathogenetic mechanisms. The natural history of pediatric AIP is obscure, and the diagnostic usefulness of different autoimmune abnormalities found in adults with AIP is limited for children. Tips to manage pediatric patients with AIP have been recently drafted through a set of recommendation statements. This review describes the current data about AIP and the pathogenic contribution of specific autoantibodies expressly in the pediatric population.

Reprint of: Pathologic manifestations of Immunoglobulin(Ig)G4-related lung disease

Immunoglobulin(Ig)G4-related disease (IgG4-RD) is a fibroinflammatory condition that can affect virtually any organ and usually presents as tumefactive lesions involving multiple sites. Characteristic histopathology of IgG4-RD consists of dense lymphoplasmacytic infiltrate, fibrosis (often in storiform pattern), and obliterative phlebitis, accompanied by tissue infiltration of IgG4-positive plasma cells with or without elevation of serum IgG4 level. Despite a general similarity in the morphologic manifestations of IgG4-RD, site-specific unique morphologic features have been described in some organs including the lung. Compared with other sites, pulmonary involvement by IgG4-RD has been recognized more recently, and lung biopsy interpretation for this condition is often challenging, as both a relative paucity of pathognomonic features and a plethora of overlapping findings with other fibroinflammatory processes of the lung. This review is focused on the morphologic spectrum of IgG4-related lung disease documented in the current literature and on the pertinent issues in the differential diagnoses with other conditions encountered in the lung.

Immunoglobulin G4 (IgG4)-Related Hypophysitis

We report two different cases of IgG4-related hypophysitis. In the first case, a pituitary lesion was accompanied by lymphocytic meningitis possibly mimicking tuberculous meningitis. The second case was unassociated with involvement of other organs. No histologic differences were noted between the two cases indicating that the morphologic features of the hypophysial lesion do not depend on the presence of other lesions. The pathogenesis of IgG4 hypophysitis is not known, and further study is necessary to explore the cause, progression, and influencing factors of this disease.

IgG4-related disease involving the esophagus: a clinicopathological study

Immunoglobulin G4 (IgG4)-related disease is a recently coined systemic disease characterized by specific histopathologic findings of an intense lymphoplasmacytic infiltrate, storiform fibrosis, and obliterative phlebitis in the presence of predominant IgG4-positive plasma cells. Although IgG4-related disease has been described in many organs, involvement of the esophagus is very rare. In this study, we describe the clinicopathologic characteristics of eight patients with IgG4-related esophagitis. We evaluated chronic esophagitis specimens with lymphoplasmacytic infiltrate obtained over the past 6 years (from January 2011 to February 2017) using a chart review, pathologic examination, and IgG4 immunohistochemical staining. The diagnoses of the specimens were either confirmed as IgG4-related esophagitis (IgG4-RE) or chronic esophagitis, not otherwise specified (CENOS), and the clinicopathologic data from each group were compared. Eight patients were diagnosed with IgG4-RE and 10 controls were identified and diagnosed with CENOS. In the IgG4-RE group, esophageal strictures were identified in three patients, two patients had postmyotomy treated achalasia, one patient had erosive esophagitis and another presented with an esophageal nodule. Only one patient had an unremarkable mucosa on endoscopy. In the CENOS group, four patients had esophageal strictures, six had erosive esophagitis, one patient had mild esophagitis. The IgG4-RE group had significantly higher numbers of IgG4-positive plasma cells (66.9 ± 21.9 vs. 4.7 ± 2.4 per high power field; P< 0.001) and a greater IgG4: IgG ratio 0.76 ± 0.13 vs. 0.06 ± 0.05; P< 0.001) when compared to CENOS patients. Two of the patients with recurrent esophageal strictures in the IgG4-RE group showed initial response to steroid therapy and are currently on immunosuppressive therapy which has significantly reduced the need for multiple esophageal dilatations. The presentation of IgG4-related esophageal disease can vary and the key to diagnosis is dependent on histopathology. These observations highlight the need for IgG4 immunohistochemical staining of esophageal biopsies especially in patients with mucosal ulceration, chronic inflammation, and plasmacytosis on biopsy. This will prevent unwarranted esophagectomies and failed medical treatment due to lack of recognition of this entity.

Detection of serum IgG4 levels in patients with IgG4-related disease and other disorders

Objective

Elevated serum IgG4 levels are an important hallmark for diagnosing IgG4-related disease (IgG4-RD), but can also be observed in other diseases. This study aimed to compare two different testing methods for IgG4: ELISA and nephelometric assay. Both assays were used to measure serum IgG4 concentrations, and to assess the prevalence of high serum IgG4 levels in both IgG4-RD and non-IgG4-RD diseases.

Methods

A total of 80 serum samples were tested using the nephelometric assay and ELISA method that we established. Serum IgG4 concentrations were determined by ELISA for 957 patients with distinct diseases, including 12 cases of IgG4-RD and 945 cases of non-IgG4-RD.

Results

IgG4 levels from 80 selected serum samples examined by ELISA were in agreement with those detected using the nephelometry assay. Meanwhile, the serum IgG4 concentrations measured by ELISA were also consistent with the clinical diagnoses of patients with IgG4-RD during the course of disease. The Elevated levels of serum IgG4 (>1.35 g/L) were detected in all IgG4-RD (12/12) patients, and the prevalence of high IgG4 serum levels was 3.39% in non-IgG4-RD cases. Among them, the positive rates of serum IgG4 were 2.06% in patients with carcinoma and 6.3% in patients with other non-IgG4 autoimmune diseases.

Conclusion

Our established ELISA method is a reliable and convenient technique, which could be extensively used in the clinic to measure serum IgG4 levels. High levels of IgG4 were observed in IgG4-RD. However, this phenomenon could also be observed in other diseases, such as carcinomas and other autoimmune diseases. Thus, a diagnosis of IgG4 disease cannot only be dependent on the detection of elevated serum IgG4 levels.

Immunoglobulin G4 related chronic sclerosing sialadenitis

Background:

ENT surgeons may be the first specialists to encounter and diagnose patients with salivary gland disease. A new entity involving the salivary glands has recently been described of which ENT surgeons need to be aware: immunoglobulin G4 related chronic sclerosing sialadenitis.

Method:

A literature search of Medline, Embase and Cochrane Library databases was performed, using the search terms ‘IgG4’, ‘hyperIgG4 syndrome’ and ‘IgG4 related chronic sclerosing sialadenitis’.

Results:

Knowledge concerning immunoglobulin G4 related chronic sclerosing sialadenitis is rapidly increasing. This new entity is part of a fibro-inflammatory corticosteroid-responsive systemic disease (immunoglobulin G4 related disease) and has been described in almost every organ. Biopsy of the submandibular gland can be diagnostic. However, the diagnosis can easily be overlooked if: clinical suspicion is not high, one is unaware of the classical morphology and/or immunoglobulin G4 staining is not performed. This paper presents a summary of the current understanding of the disease and its management.

Conclusion:

ENT surgeons should be aware of this new disease entity. Patients with systemic disease should be managed under a multidisciplinary team, with input from clinicians who have an interest in such diseases (such as gastroenterologists and rheumatologists), and input from histopathologists and radiologists.

Sudden cardiac death due to coronary artery involvement by IgG4-related disease: a rare, serious complication of a rare disease

Immunoglobulin G4-related disease (IgG4-RD) is a systemic disorder characterized by multiorgan fibrosis with IgG4-producing plasma cells, increased IgG4 serum concentration, and responsiveness to steroid therapy. Involvement of the pancreas, salivary glands, orbit, aorta, and other sites has been well documented in the literature; however, there have been limited reports of cases involving the coronary arteries. We report the case of a 53-year-old Hispanic man who was brought to the emergency center and diagnosed with sudden cardiac death. Autopsy was subsequently performed, revealing multiorgan involvement by IgG4-RD, including involvement of the coronary arteries. The inflammation and fibrosis, in combination with concomitant atherosclerotic disease, resulted in severe stenosis of the coronary arteries. Two of the coronary arteries were further occluded by thrombosis. These factors led to cardiac hypoperfusion, myocardial infarction and, ultimately, sudden cardiac death. Fatal involvement of the coronary arteries has not been previously reported, raising a new concern for a severe complication of IgG4-RD.

Histological evaluation of obliterative phlebitis for the diagnosis of autoimmune pancreatitis

BACKGROUND

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.

METHODS

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.

RESULTS

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 1 cm(2) of OVL-1 were high for LPSP. Maximum diameter of OVL-1 ≥150 μm was observed in 17 LPSP, 0 CP, and 1 PDA cases (sensitivity 94.4 %, specificity 98.6 %).

CONCLUSIONS

Additional EVG is useful for excluding conditions mimicking OVL-1 or detecting OVL in small specimens. The presence of OVL-1 with diameter ≥150 μm is highly diagnostic for LPSP.

IgG4-related orbital disease: a meta-analysis and review

IgG4-related orbital disease (IgG4-ROD) is a recently described condition that may account for a significant proportion of idiopathic lymphoplasmacytic or sclerotic orbital lesions. This study is the first meta-analysis of published cases and reveals several differences between IgG4-related disease affecting the orbit and that affecting the pancreas. IgG4-ROD affects a slightly younger group of patients, affects men and women approximately equally, is commonly associated with salivary gland lesions, is associated with a relatively higher serum IgG4 and may confer an increased risk of non-Hodgkin Lymphoma. Its pathogenesis may involve an immune response to antigen exposure in the upper aerodigestive tract.

Pulmonary inflammatory myofibroblastic tumor and IgG4-related inflammatory pseudotumor: a diagnostic dilemma

IgG4-related inflammatory pseudotumor (IPT) and inflammatory myofibroblastic tumor (IMT) share morphological features like a prominent fibroblastic/myofibroblastic proliferation and the presence of inflammatory cells. Since IPT is managed conservatively and IMT is treated by surgical excision, it is important to differentiate these two lesions. The aim of this study is to highlight morphological and immunohistochemical features that distinguish IPT and IMT. Clinicopathological characteristics of cases diagnosed as pulmonary IPT or IMT from 1997 to 2013 were reviewed. The histological features were studied on hematoxylin and eosin-stained sections. Immunohistochemistry was done for IgG, IgG4, ALK-1, SMA, desmin, and CD34 for classification into IPT and IMT. Of the ten patients, seven were male and the age ranged from 4 to 58 years. The tumor size ranged from 1.5 to 4.0 cm in diameter. Histologically, proliferation of bland-looking spindle cells along with fibrosis and an inflammatory infiltrate comprising of lymphocytes and plasma cells were the common morphological features of both lesions. The spindle cell proliferation was more marked in IMT whereas lymphoplasmacytic infiltrate was more prominent in IPT. Obstructive phlebitis was observed only in cases of IPT. IgG4 expression was noted in IPT, and the number of IgG4-positive plasma cells and the ratio of IgG4+/IgG+ plasma cells were significantly lower in IMT than in IgG4-related IPT. Expression of anaplastic lymphoma kinase (ALK) was observed only in IMT, but not in IgG4-related IPT. The proportion of proliferating spindle cells, lymphoplasmacytic infiltrate, obstructive phlebitis, IgG4+ plasma cells and the ratio of IgG4+/IgG+ plasma cells, and ALK expression are helpful in differentiating these morphologically similar but biologically different lesions, which require different treatment modalities.

Infiltration of peritumoural but tumour-free parenchyma with IgG4-positive plasma cells in hilar cholangiocarcinoma and pancreatic adenocarcinoma

BACKGROUND

Recently, new guidelines for diagnosing IgG4-associated cholangitis have been published devaluing the diagnostic significance of IgG4-positive plasma cells and steroid trials. We sought to evaluate the utility of IgG4-positive plasma cells in discriminating IgG4-associated cholangitis from hilar cholangiocarcinoma and autoimmune pancreatitis from pancreatic adenocarcinoma under conditions when malignancy is likely to be missed.

METHODS

Resection specimens obtained from patients with hilar cholangiocarcinoma, pancreatic adenocarcinoma or hepatocellular carcinoma were re-evaluated for IgG4-positivity. Histological analysis focussed on peritumoural but tumour-free sections. Perioperative biochemical and clinical data were reviewed.

RESULTS

Nineteen patients with hilar cholangiocarcinoma and 29 patients with pancreatic adenocarcinoma were eligible for histological re-evaluation. Six of 19 (32%) patients with hilar cholangiocarcinoma and 5 of 29 (17%) patients with pancreatic adenocarcinoma were IgG4-positive (≥20 IgG4-positive plasma cells per high power field). Patients with IgG4-positive hilar cholangiocarcinoma showed significantly higher levels of serum total bilirubin (3.6mg/dl vs. 1.8mg/dl; P<0.05) and serum alanine-aminotransferase (median 343U/l vs. 63U/l, P<0.05) compared to IgG4-negative patients with hilar cholangiocarcinoma.

CONCLUSIONS

IgG4-positive plasma cells are of limited utility especially in distinguishing hilar cholangiocarcinoma from IgG4-associated cholangitis even when combined with clinical parameters and may be misleading under conditions when malignancy is missed.

Assessment of pathologically diagnosed patients with Castleman's disease associated with diffuse parenchymal lung involvement using the diagnostic criteria for IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4RD) is a recently recognized disease entity. Differentiating IgG4RD from plasma cell type Castleman's disease (PCD) is important but also difficult using only pathological findings. In addition, little is known about the association between these two diseases with diffuse parenchymal lung involvement.

METHODS

We analyzed the serum IgG4 levels and the ratio of IgG4/IgG-positive plasmacytes in the lung and lymph node specimens of eight patients previously pathologically diagnosed of PCD with diffuse parenchymal lung involvement (DL-PCD). We also compared the clinical and laboratory findings observed in these patients.

RESULTS

Six of the eight patients exhibited abundant IgG4-positive plasmacytes in the lung and lymph node tissues and elevated serum IgG4 levels, thereby fulfilling the diagnostic criteria of IgG4RD with DL (DL-IgG4RD) in addition to having obstructive phlebitis and massive lymphoplasmacytic infiltration with fibrosis. However, three of these six patients exhibited higher levels of serum interleukin-6 and were still diagnosed with DL-PCD. Accordingly, three of these eight patients were considered as IgG4RD with DL (DL-IgG4RD), and the other five patients were ultimately given a diagnosis of DL-PCD. These two diseases have different characteristics in terms of age, symptoms, serum levels of C-reactive protein, and IgA, complicating allergic disorders, response to corticosteroids, and prognosis.

CONCLUSIONS

This is the first report to show a high prevalence of DL-IgG4RD in DL-PCD patients, although additional large investigations are necessary. Clinical and laboratory findings are important for distinguishing between these two diseases in other organs, as previously described.

IgG4-related disease and hypertrophic pachymeningitis

Hypertrophic pachymeningitis (HP) is an inflammatory condition in which the dura mater of the cranium or spine becomes thickened, leading to symptoms that result from mass effect, nerve compression, or vascular compromise. The differential diagnosis of HP includes immune-mediated conditions such as rheumatoid arthritis and vasculitis, malignancies, and infections. Many times, no diagnosis is reached; in such cases, the disease has been described as idiopathic HP. IgG4-related disease (IgG4-RD) is a recently described inflammatory condition known to cause tumefactive lesions at myriad anatomical locations. Both IgG4-RD and idiopathic HP share similar demographics, histopathology, and natural history. We hypothesized that IgG4-RD is a common cause of idiopathic HP.To investigate this hypothesis, we identified all pathology specimens diagnosed as noninfectious HP during 25 years at our institution. Fourteen cases had stained slides and paraffin blocks to permit review of the original hematoxylin and eosin stained slides as well as immunostaining of cell blocks. Recently published consensus guidelines describing characteristic histopathology and the necessary quantity of IgG4+ plasma cell infiltrate were used to diagnose IgG4-RD.Four cases (66.6%) that had been regarded previously as representing idiopathic HP were diagnosed as IgG4-RD; of all the reviewed cases, IgG4-RD represented 29% of cases. Of the remaining cases, 3 cases were associated with granulomatosis with polyangiitis (GPA), 2 with lymphoma, and 1 each with rheumatoid arthritis, giant cell arteritis, and sarcoidosis. Two of the cases could not be diagnosed more precisely and were classified as undifferentiated HP. Clinical history, serologic tests, cerebrospinal fluid studies, and radiology alone could not identify the cause of HP. Rather, biopsy with histopathology and immunostaining was necessary to reach an accurate diagnosis. Significant IgG4+ plasma cell infiltrates were observed in rheumatoid arthritis, granulomatosis with polyangiitis, and lymphoma, underscoring the importance of histopathology in making the diagnosis of IgG4-RD.This case series demonstrates that IgG4-RD may be the most common etiology of noninfectious HP and highlights the necessity of biopsy for accurate diagnosis.

IgG4-associated cholangitis

IgG4-associated cholangitis is the hepatobiliary manifestation of a recently characterized inflammatory systemic disease, associated with increased IgG4 serum levels and IgG4-positive lymphoplasmacytic infiltration. Often, patients present with obstructive jaundice, and imaging reveals stenoses of the extrahepatic or intrahepatic bile ducts, often in association with parenchymal pancreatic findings and irregularities of the pancreatic duct. The histologic findings include lymphoplasmacytic infiltrates, on occasion resulting in tumefactive lesions (which can mimic malignancy), obliterative phlebitis, and fibrotic changes. Steroid treatment is the mainstay of management, but relapse is common after discontinuation of therapy or during tapering of steroids and may require further treatment.

IgG4-related diseases

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a fascinating condition recognised as a systemic disease in 2003 [1,2]. The first link between autoimmunity affecting the pancreas, elevated serum IgG4 concentrations and large numbers of IgG4-positive plasma cells in pancreatic tissue was described only 2 years earlier [3]. Since then, many diseases that have long been viewed organ-specific are now considered within the spectrum of IgG4-RD. Practically any organ can be affected, having in common a key pathological feature consisting in dense lymphocyte and plasma cell infiltrate rich in IgG4-positive plasma cells, storiform fibrosis and often an elevated serum IgG4 concentration. While good clinical response to steroid therapy is observed, immunosuppressive or B-cell depleting therapy can be required. It is important to distinguish the IgG4-RD from traditional organ-specific autoimmune disease to guide therapy.

Immunoglobulin G4-related disease mimicking asthma

Immunoglobulin (Ig) G4-related disease (also known as 'IgG4-related sclerosing disease', 'IgG4-related systemic disease' or 'hyper-IgG4-disease') is a recently recognized systemic fibroinflammatory disease associated with IgG4-positive plasma cells in tissue lesions. IgG4-related disease was initially described as autoimmune pancreatitis, but it is now known to affect virtually any organ. The authors describe a patient presenting with multi-organ manifestations, including airway inflammation mimicking asthma, pulmonary parenchymal infiltrates, intrathoracic lymphadenopathy, submandibular gland swelling and a kidney mass.

Pathologic manifestations of Immunoglobulin(Ig)G4-related lung disease

Immunoglobulin(Ig)G4-related disease (IgG4-RD) is a fibroinflammatory condition that can affect virtually any organ and usually presents as tumefactive lesions involving multiple sites. Characteristic histopathology of IgG4-RD consists of dense lymphoplasmacytic infiltrate, fibrosis (often in storiform pattern), and obliterative phlebitis, accompanied by tissue infiltration of IgG4-positive plasma cells with or without elevation of serum IgG4 level. Despite a general similarity in the morphologic manifestations of IgG4-RD, site-specific unique morphologic features have been described in some organs including the lung. Compared with other sites, pulmonary involvement by IgG4-RD has been recognized more recently, and lung biopsy interpretation for this condition is often challenging, as both a relative paucity of pathognomonic features and a plethora of overlapping findings with other fibroinflammatory processes of the lung. This review is focused on the morphologic spectrum of IgG4-related lung disease documented in the current literature and on the pertinent issues in the differential diagnoses with other conditions encountered in the lung.

[Hypophysitis: increasingly complex clinicopathological spectrum!]

Hypophysitis is a chronic inflammation of the pituitary gland that comprises an increasingly complex clinicopathological spectrum. Lymphocytic and granulomatous hypophysitis are the most common forms, but new variants have recently been reported such as IgG4-related hypophysitis that is identified by well-defined criteria. For the first time, hypophysitis in ANCA-associated vasculitides has been reported. Monoclonal antibodies directed against the cytotoxic T-lymphocyte antigen-4 (CTLA-4), investigated in metastatic melanoma, can induce hypophysitis. Hypophysitis's pathogenesis remains obscure but several candidate pituitary autoantigens have been described in the last decade, although none has proven useful as a diagnostic tool.

Is IgG4-Related Disease a Cause of Xerostomia? A Cohort Study of 60 Patients

Objective. Immunoglobulin-G4-(IgG4-) related disease (IgG4 RD) is a fibrosing process characterized by a significant infiltration of IgG4-secreting plasma cells. IgG4 RD can affect almost all organs including salivary glands. Whether IgG4 RD plays a role in the development of sicca syndrome and particularly dry mouth syndrome remains to be investigated. Methods. We conducted a monocentric cohort study for two years to search for IgG4 RD features in patients with dry mouth syndrome using immunostainings of labial salivary gland specimens with anti-IgG4 antibody. Results. Among 60 patients presenting with dry mouth syndrome who underwent labial salivary gland biopsy, 18 showed positive immunostaining with the anti-IgG4 antibody including 4 patients with typical systemic IgG4 RD. Five also fulfilled criteria for Sjögren's syndrome. Conclusion. These findings suggest that clinical forms of IgG4 RD salivary involvement without salivary swelling may occur. This salivary involvement is probably overlooked in everyday practice and could represent a mild form of IgG4 RD.

Recent advances in research of immunoglobulin G4-related sclerosing cholangitis

Immunoglobulin G4-related sclerosing cholangitis (IgG4-SC) is a recently defined disease entity characterized by elevated serum IgG4, chronic progressive obstructive jaundice, and diffuse or mass-forming inflammatory reaction rich in IgG4-positive plasma cells and lymphocytes associated with fibrosclerosis and obliterative phlebitis, which shares a number of clinical, biochemical, and radiological features with primary sclerosing cholangitis (PSC) or cholangiocarcinoma (CC). IgG4-SC is commonly associated with autoimmune pancreatitis (AIP). Steroid therapy comprises the mainstay of treatment for IgG4-SC patients. However, liver transplantation is the only useful treatment for PSC patients, and CC patients require surgical therapy. Therefore, the accurate discrimination between IgG4-SC and PSC or CC is a very important issue. In this article, we will review the features and role of immunoglobulin G4 (IgG4), the diagnosis and therapy of IgG4-SC, and the relations between IgG4-SC and AIP, PSC or CC.

Autoantibodies in autoimmune pancreatitis

Autoimmune pancreatitis (AIP) was first used to describe cases of pancreatitis with narrowing of the pancreatic duct, enlargement of the pancreas, hyper-γ-globulinaemia, and antinuclear antibody (ANA) positivity serologically. The main differential diagnosis, is pancreatic cancer, which can be ruled out through radiological, serological, and histological investigations. The targets of ANA in patients with autoimmune pancreatitis do not appear to be similar to those found in other rheumatological diseases, as dsDNA, SS-A, and SS-B are not frequently recognized by AIP-related ANA. Other disease-specific autoantibodies, such as, antimitochondrial, antineutrophil cytoplasmic antibodies or diabetes-specific autoantibodies are virtually absent. Further studies have focused on the identification of pancreas-specific autoantigens and reported significant reactivity to lactoferrin, carbonic anhydrase, pancreas secretory trypsin inhibitor, amylase-alpha, heat-shock protein, and plasminogen-binding protein. This paper discusses the findings of these investigations and their relevance to the diagnosis, management, and pathogenesis of autoimmune pancreatitis.

Increased IgG4-Positive Plasma Cells in Granulomatosis with Polyangiitis: A Diagnostic Pitfall of IgG4-Related Disease

Granulomatosis with polyangiitis (Wegener's) (GPA) may mimic IgG4-related disease (IgG4-RD) on histologic examination of some biopsies, especially those from head and neck sites. IgG4 immunostain is often performed in this context for differential diagnosis with IgG4-RD. However, the prevalence of IgG4+ cells in GPA has not been explored. We examined the IgG4+ cells in 26 cases confirmed as GPA by a thorough clinical and pathologic assessment. Twenty-six biopsies consisted of 14 sinonasal/oral cavity/nasopharynx, 7 orbit/periorbital, 3 lung/pleura, 1 iliac fossa/kidney, and 1 dura specimens. Eight of 26 (31%) biopsies revealed increased IgG4+ cells (>30/HPF and >40% in IgG4+/IgG+ ratio). The IgG4+ cells and IgG4+/IgG+ ratio ranged 37–137/hpf and 44–83%, respectively. Eight biopsies with increased IgG4+ cells were from sinonasal (n = 4) or orbital/periorbital (n = 4) sites. In conclusion, increased IgG4+ cells are not uncommonly seen in sinonasal or orbital/periorbital biopsies of GPA, which could pose as a diagnostic pitfall.