IgG4-Related Fibrotic Diseases from an Immunological Perspective: Regulators out of Control?

Myofibroblast and pro-fibrotic cytokines in fibrosis of IgG4-related disease (IgG4-RD) patients from South Asia: preliminary data

INTRODUCTION

Fibrosis is a typical pathological characteristic in IgG4-RD patients and often irreversible. There exists a lack of suitable markers for detection of earlier onset of fibrosis in various organs in IgG4-RD patients. Hence, this study aims at analysing ambispectively the myofibroblasts and the pro-fibrotic cytokines, IFN gamma and IL-33 involved in IgG4-RD associated fibrosis in South Asian patients.

METHOD

Archived biopsy samples of definite/probable/possible cases of IgG4-RD, classified according to diagnostic criteria, taken from patients who attended the OPD and IPD of our tertiary care centre during January 2015-January 2020 were chosen for this study. The paraffin sections were examined qualitatively for fibrosis and the excessive collagen deposition by Hematoxylin & Eosin and Masson's Trichrome staining. Also, the presence of alpha-Smooth muscle actin (α-SMA) expressing myofibroblasts and the involvement of pro-fibrotic cytokines (IFN-gamma, IL-33) were assessed by Immunohistochemistry and scored semi-quantitatively (+mild, ++moderate, +++ severe). Serum IL-33 levels were analysed by indirect Elisa (R & D Systems).

RESULTS

Myofibroblasts were present in 10/12 biopsy samples, in moderate levels in 4 (33%) and very high levels (+++) in 3 (25%) of the patients. IFN-gamma was expressed at low levels in 6 (50%) and absent in 6 (50%). All patients showed IL-33 expression with very high levels in tissue (6, 50%), as well as in serum samples.

CONCLUSION

The findings of this study reinforce the role of myofibroblasts and profibrotic cytokines like IL-33 in fibrosis of Ig4-RD patients, pointing to their potential as earlier predictive markers of onset and extent of fibrosis.

Activation and Regulation of Pancreatic Stellate Cells in Chronic Pancreatic Fibrosis: A Potential Therapeutic Approach for Chronic Pancreatitis

In the complex progression of fibrosis in chronic pancreatitis, pancreatic stellate cells (PSCs) emerge as central figures. These cells, initially in a dormant state characterized by the storage of vitamin A lipid droplets within the chronic pancreatitis microenvironment, undergo a profound transformation into an activated state, typified by the secretion of an abundant extracellular matrix, including α-smooth muscle actin (α-SMA). This review delves into the myriad factors that trigger PSC activation within the context of chronic pancreatitis. These factors encompass alcohol, cigarette smoke, hyperglycemia, mechanical stress, acinar cell injury, and inflammatory cells, with a focus on elucidating their underlying mechanisms. Additionally, we explore the regulatory factors that play significant roles during PSC activation, such as TGF-β, CTGF, IL-10, PDGF, among others. The investigation into these regulatory factors and pathways involved in PSC activation holds promise in identifying potential therapeutic targets for ameliorating fibrosis in chronic pancreatitis. We provide a summary of recent research findings pertaining to the modulation of PSC activation, covering essential genes and innovative regulatory mediators designed to counteract PSC activation. We anticipate that this research will stimulate further insights into PSC activation and the mechanisms of pancreatic fibrosis, ultimately leading to the discovery of groundbreaking therapies targeting cellular and molecular responses within these processes.

Thoracic manifestations of IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year. The disease can affect virtually any organ and is characterized by unifying histopathological findings. Recently, four subgroups of patients have been characterized: hepatobiliary, head and neck, Mikulicz syndrome and retroperitoneal fibrosis, who illustrate the mainly abdominal and ENT tropism of the disease. Yet, thoracic involvement is not uncommon. It can be detected in up to 30% of patients with systemic IgG4-RD and is the exclusive manifestation of the disease in about 10% of cases. Clinical symptoms are nonspecific and may include dyspnoea, cough or chest pain. Chest CT findings are heterogeneous and primarily include peribronchovascular thickening, nodules, ground-glass opacities and lymphadenopathy. There is no specific diagnostic test for IgG4-RD thoracic involvement, which may mimic malignancy or vasculitis. Therefore, a cautious approach is needed to make an accurate diagnosis: a search for extra-thoracic manifestations, elevated serum IgG4 levels, circulating levels of plasmablasts and pathologic evidence of disease is warranted. Although very suggestive, neither the presence of a polyclonal IgG4 lymphoplasmacytic infiltrate, storiform fibrosis or obliterative phlebitis are sufficient to confirm the histological diagnosis. Steroids are recommended as first-line therapy. Rituximab or disease-modifying antirheumatic drugs may be used in relapsed or rare cases of steroid-refractory disease. In this review, we summarize current knowledge regarding the pathophysiology, epidemiology, diagnostic modalities (clinical-biological-imaging-histopathology) and treatment of IgG4-RD thoracic involvement.

Concomitant adult onset xanthogranuloma and IgG4-related orbital disease: a rare occurrence

Adult onset xanthogranulomatous disease is a rare orbital disease. IgG4-related disease is a systemic disease that can often manifest in the orbit. In this communication, we present the case of a patient with a xanthelasma-like lesion on the upper eyelid, and an enlarged lacrimal gland, which on biopsy was diagnosed as an orbital xanthogranuloma. Detailed serological workup showed that the patient was found to have elevated serum IgG4 levels. The orbital specimen was re-stained and found to be positive for IgG4. The patient was treated with oral steroids with partial resolution of the lesion. This is an interesting case of both histopathological adult onset xanthogranuloma (AOX) and IgG4-related orbital disease (IgG4-ROD). The early evidence suggests that the diagnosis of one of these disorders should point the physician to investigate for the presence of the other, especially if xanthogranulomatous disease is diagnosed first.

The Possible Pathogenic Role of IgG4-Producing Plasmablasts in Stricturing Crohn's Disease

BACKGROUND

Crohn's disease (CD) is a condition on the spectrum of inflammatory bowel disease that affects up to 20 people per 100,000 in the US annually, and with incidence increasing. One of the most significant sources of morbidity in CD is the formation of strictures, with resultant intestinal blockage a common indication for hospitalization and surgical intervention in these patients. The pathophysiology of stricture formation is not fully understood. However, the fibroplasia that leads to fibrostenotic stricture formation may have shared pathophysiology with IgG4-related fibrosis.

SUMMARY

Initial intestinal inflammation recruits innate immune cells, such as neutrophils, that secrete IL-1β and IL-23, which induces a type 17 CD4+ T-helper T-cell (Th17)-mediated adaptive immune response. These CD4+ Th17 T cells also contribute to inflammation by secreting proinflammatory cytokines such as IL-17 and IL-21. IL-21 recruits and stimulates CD4+ T follicular helper (Tfh) cells, which secrete more IL-21. This causes ectopic germinal center formation, recruiting and stimulating naïve B cells. The IL-17 and IL-21 produced by Th17 cells and Tfh cells also induce IgG4 plasmablast differentiation. Finally, these IgG4-producing plasmablasts secrete platelet-derived growth factor (PDGF), which activates local PDGF-receptor expressing fibroblasts and myofibroblasts, resulting in uncontrolled fibroplasia.

Mimickers of pulmonary lymphoma

There are multiple entities that involve the lung that have radiographic, clinical, and morphologic overlaps with pulmonary lymphoma. In this review, we will discuss these entities in detail and provide relevant updates.

IgG4-Related Disease coexisting with Behçet's Disease

We describe a case of Immunoglobulin G4-related disease (IgG4-RD) coexisting with Behçet’s disease. A 49-year-old man, with a diagnosis of Behçet’s Disease for 15 years who was found to have an acute kidney injury. His investigations revealed an elevated IgG4 level and the abdominal computerized tomography showed a retroperitoneal mass, which was diagnosed to be IgG4-RD based on histology. The patient showed symptomatic and radiological improvement after starting high dose steroid for 1 month followed by a maintenance dose. Our case report suggested that the two diseases arose separately.

IgG4-Related Lung Disease Exhibiting the Invasion into the Diaphragm: A Case Report

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition which involves various organs. This is a very rare case of IgG4-related lung disease (IgG4-RLD) with the invasion into diaphragm. The patient was a 71-year-old man with a long-term exposure to asbestos who had a mass shadow in the left lower lung lobe, which was suspected to invade the left diaphragm on computed tomography (CT). Positron emission tomography (PET)/CT also presented an avid intake of fluorodeoxyglucose in the mass, which suspected lung cancer. Although bronchoscopic biopsy could not lead to the definite diagnosis, we performed left lower lobectomy combined with the resection of left diaphragm. The specimen showed the features of IgG4-RLD on pathology: the vein stenosis and fibrosis around the vein, the infiltration of IgG4-positive cells, and IgG cells to IgG4 cells ratio of 40%. Furthermore, there were inflammatory cells infiltrating to the diaphragm.

Neuro-ophthalmic complications of IgG4-related disease

PURPOSE OF REVIEW

IgG4-related disease (IgG4-RD) is increasingly recognized as a fibroinflammatory disease with a plethora of organ-specific manifestations but a particular predilection for head and neck tissues, including the nervous system. This review discusses general features and organ-specific presentations of IgG4-RD as well as treatment considerations, particularly emphasizing features of neuro-ophthalmic interest.

RECENT FINDINGS

IgG4-RD is emerging as a common cause of several fibroinflammatory disorders in the head and neck that were previously considered idiopathic, such as sclerosing orbital pseudotumor, orbital myositis, hypophysitis, and hypertrophic pachymeningitis. New and unusual presentations continue to be described, including a number of vascular manifestations. Substantial progress has been made in elucidating the cell types involved in IgG4-RD, and new pathogenic models are being proposed. Although clinicopathologic correlation remains the cornerstone of diagnosis, ancillary tests such as flow cytometry for circulating plasmablasts and PET-computed tomography have high sensitivity, and certain radiologic features are recognized to be particularly suggestive, such as infraorbital nerve enlargement in IgG4-RD orbitopathy. IgG4-RD often responds to steroids but incomplete responses and relapses are common. Rituximab is emerging as a promising new therapy.

SUMMARY

The current review summarizes manifestations of IgG4RD that are of particular relevance to neuro-ophthalmic practice.

The impact of IgG-4-ROD on the diagnosis of orbital tumors: A retrospective analysis

This study was to determine the prevalence of immunoglobulin G4 (IgG4)-related orbital disease (IgG4-ROD) among patients who have previously undergone biopsy and were diagnosed to have idiopathic orbital inflammatory disease (IOID) or orbital lymphoproliferative disease (OLD), namely, lymphoma and benign reactive lymphoid hyperplasia (BRLH). This is a retrospective cross-sectional study. The charts and slides of all patients who underwent biopsies and were histopathologically diagnosed to have either IOID or OLD were reviewed. Demographics, clinical features, initial histopathological diagnoses, treatment received, and final outcome were noted. Using the diagnostic criteria for diagnosis for IgG4 disease, those cases that would classify as "possible IgG4-related disease (IgG4-RD)" were reviewed, reclassified, and reassigned a diagnosis of IgG4-ROD. We reviewed 105 patients' clinical charts. Of these 105 patients, upon reviewing the histopathology, 18 (17.15%) patients were found to fit the diagnostic criteria for possible IgG4-ROD. Of these 18 patients who were now reassigned the diagnosis of IgG4-ROD, the most common previous histopathological diagnosis was found to be IOID, for eight patients (44%), then BRLH, which was noted in five patients (27.8%), followed by lymphoma, which was noted in two patients (11.1%). Previously diagnosed cases of IOID and OLD were found to fulfill the criteria for IgG4-ROD. Given the advent of recent diagnostic and histopathological techniques, all cases of suspected IOID and OLD should be screened for IgG4-ROD and all previously diagnosed cases must be closely followed up, given the systemic implication of IgG4-RD. Histopathological reassessment of previously diagnosed cases may be considered.

Immunoglobulin G4-Related Thyroid Diseases

Immunoglobulin G4-related disease (IgG4-RD) is a new disease category involving many organ systems, including the endocrine system in general and the thyroid in particular. Since an initial association was made between hypothyroidism and autoimmune (IgG4-related) pancreatitis, more forms of IgG4-related thyroid disease (IgG4-RTD) have been recognized. Four subcategories of IgG4-RTD have so far been identified: Riedel thyroiditis (RT), fibrosing variant of Hashimoto thyroiditis (FVHT), IgG4-related Hashimoto thyroiditis, and Graves disease with elevated IgG4 levels. Although a male predominance is seen for IgG4-RD in general, RT and FVHT have a female preponderance. The pathogenesis of IgG4-RD is not completely understood; however, genetic factors, antigen-antibody reactions, and an allergic phenomenon have been described. Diagnosis of IgG4-RD requires a combination of clinical features, serological evidence, and histological features. Histology is the mainstay of diagnosis, with IgG4 immunostaining. Although serum IgG4 levels are usually elevated in IgG4-RD, raised serum IgG4 is neither necessary nor adequate for diagnosis. Imaging supports the diagnosis and is a useful tool in disease monitoring. Management of IgG4-RTD is both medical and surgical. Steroids are the first-line treatment and may produce a swift response. Tamoxifen and rituximab are second-line agents used in steroid-resistant patients. Surgical debulking is carried out in RT solely as a procedure to relieve obstruction. Other endocrine associations described with IgG4-RD are hypophysitis and Hashimoto encephalopathy. IgG4-RTD is an uncommon disease entity, and prompt diagnosis and treatment can improve outcomes.

IgG4 related lung disease extending to the thoracic vertebrae

IgG4-related disease (IgG4-RD) is a fibroinflammatory condition that can affect practically every organ. Although it was first identified in pancreas and salivary glands, major organs like liver, biliary tree, kidney, thyroid glands and lungs are commonly involved, sometimes resulting in organ failure. We describe a case of an 41-year-old man presented with back pain after a rotator cuff injury. A Computed Tomography (CT) revealed incidentally a right lower lobe paravertebral lesion extending across the T5 and T6 vertebral levels and invading into the adjacent pleural surface. The laboratory findings and the CT guided biopsy were inconclusive. Morphological and immunohistochemical findings after a lung biopsy by video-assisted thoracic surgery (VATS) were suggestive to IgG4-related lung disease (IgG4-RLD), which was confirmed with high serum levels of IgG4. This represents the first case of a IgG4-RLD lesion located in the mediastinum and extending to the adjacent pleural surface and vertebrae and should be included in the differential diagnosis of posterior mediastinal masses.

Immunoglobulin G4-related disease mimicking an epidural spinal cord tumor: case report

The authors report a case of immunoglobulin G4-related disease (IgG4-RD) presenting as a paraspinal, epidural mass. This disease encompasses a host of autoimmune conditions that were previously thought to be separate entities. It is characterized by fibrosis, mediated by the aberrant proliferation and tissue invasion of IgG4-positive plasma cells, which can occur in any organ. As with other autoimmune conditions, it tends to be responsive to steroids and other immunosuppressants. It can rarely present as a tumefactive lesion of the central nervous system, creating the potential for misdiagnosis (given its similar radiological appearance to malignancy) and mistreatment. In 2015, a panel of experts convened to set forth guidelines for the diagnosis and treatment of IgG4-RD. In the case presented here, the patient initially presented with pain and weakness in the left upper extremity. Initial neuroimages revealed a contrast-enhancing mass extending from C-4 to T-1, invading the epidural spinal canal, encasing the exiting nerve roots, infiltrating the paraspinal musculature, and surrounding the left vertebral artery. A PET scan confirmed the mass was hypermetabolic, but results of fine-needle aspiration and CT-guided biopsy were inconclusive. Open biopsy yielded fibrotic tissue that met the pathological criteria for IgG4-RD: lymphoplasmacytic infiltrate, fibrosis in a storiform pattern, and obliterative phlebitis. The patient was treated with 2 doses of 4 mg of dexamethasone (Decadron) and then 50 mg of prednisone per day. Within 2 weeks, the mass was radiologically shown to have drastically decreased in size. The prednisone dose was decreased to 40 mg per day, and 100 mg of azathioprine per day was added. The patient continued to improve and the mass continued to decrease over the next 6 months. Currently, she has been weaned from all steroids and will be maintained on a daily dose of 100 mg of azathioprine.

The Developmental History of IgE and IgG4 Antibodies in Relation to Atopy, Eosinophilic Esophagitis, and the Modified TH2 Response

A common reaction from anyone confronted with allergy is the question: what prevents universal allergy? We will discuss recent findings in the mouse system that have provided us with clues on why allergy is not more common. We will also address one crucial aspect of atopic allergy in humans, which is absent in most mouse model systems, an IgG/IgE ratio <10. We consider the typical mouse IgE response to be more closely related to the "modified TH2" response in humans. We will discuss the similarities and differences between the IgE and IgG4 response to allergens and an update on the IgG4 B cell, partly derived from studies on eosinophilic esophagitis and IgG4-related diseases.

IgG4-related disease: current challenges and future prospects

Immunoglobulin G4-related disease (IgG4-RD) represents an immune-mediated fibroinflammatory condition with a characteristic histopathological appearance that can affect various organs. Although numerous single-organ manifestations have been described more than a century ago, its systemic nature and unique features were only discovered in the last 2 decades, when IgG4-RD emerged as a new entity of disease. IgG4-RD is usually considered a rare disease, but its true epidemiology has not yet been fully clarified. Also, despite recent advances in the identification of the underlying immunological processes, its pathophysiology is only incompletely understood till now. The diagnostic workup of IgG4-RD is complex and usually requires a combination of clinical examination, imaging, histological, and serological analyses. However, no finding alone is specific for IgG4-RD. Therefore, its diagnosis requires careful interpretation of examination results in context with the patient’s clinical appearance as well as the exclusion of a broad variety of differential diagnoses. The past years brought rapid advances concerning this novel disease entity: diagnostic criteria, further insights into the underlying immunological processes, new biomarkers, and novel therapeutic approaches were proposed and widened the knowledge in the field of IgG4-RD. Still, a greater number of questions remain unanswered, and many recent developments require further discussion and proof from clinical trials. This review should give an overview on current knowledge and future perspectives in epidemiology, pathophysiology, diagnosis, and therapy of IgG4-RD.

Clinical review of pulmonary manifestations of IgG4-related disease

IgG4-related disease (IgG4-RD) is a recently recognized systemic disease characterized by tumefactive lesions in various organ systems. The list of organs that can be involved continues to expand, and recently computed tomography (CT) descriptions of the pulmonary lesions found in the disease have been described. The clinical symptoms are nonspecific and may include cough, dyspnea, chest pain, and fever. The appropriate clinical presentation along with elevated serum IgG4 concentrations and pathologic evidence of lymphoplasmacytic infiltrates with abundant IgG4-positive plasma cells and storiform fibrosis is consistent with the disease. Steroids are used to treat this disease in addition to immunosupressives such as cyclosporine or rituxumab for steroid refractory disease. The pulmonary manifestations and imaging features can often mimic malignancy, and as such knowledge of the diagnostic, clinicopathologic, and radiographic features of the disease is required in order to provide appropriate diagnostic workup and treatment.

Immunology of IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition that derives its name from the characteristic finding of abundant IgG4(+) plasma cells in affected tissues, as well as the presence of elevated serum IgG4 concentrations in many patients. In contrast to fibrotic disorders, such as systemic sclerosis or idiopathic pulmonary fibrosis in which the tissues fibrosis has remained largely intractable to treatment, many IgG4-RD patients appear to have a condition in which the collagen deposition is reversible. The mechanisms underlying this peculiar feature remain unknown, but the remarkable efficacy of B cell depletion in these patients supports an important pathogenic role of B cell/T cell collaboration. In particular, aberrant T helper type 2 (Th2)/regulatory T cells sustained by putative autoreactive B cells have been proposed to drive collagen deposition through the production of profibrotic cytokines, but definitive demonstrations of this hypothesis are lacking. Indeed, a number of unsolved questions need to be addressed in order to fully understand the pathogenesis of IgG4-RD. These include the identification of an antigenic trigger(s), the implications (if any) of IgG4 antibodies for pathophysiology and the precise immunological mechanisms leading to fibrosis. Recent investigations have also raised the possibility that innate immunity might precede adaptive immunity, thus further complicating the pathological scenario. Here, we aim to review the most recent insights on the immunology of IgG4-RD, focusing on the relative contribution of innate and adaptive immune responses to the full pathological phenotype of this fibrotic condition. Clinical, histological and therapeutic features are also addressed.

Increased IgG4 responses to multiple food and animal antigens indicate a polyclonal expansion and differentiation of pre-existing B cells in IgG4-related disease

Background

IgG4-related disease (IgG4-RD) is a systemic fibroinflammatory condition, characterised by an elevated serum IgG4 concentration and abundant IgG4-positive plasma cells in the involved organs. An important question is whether the elevated IgG4 response is causal or a reflection of immune-regulatory mechanisms of the disease.

Objectives

To investigate if the IgG4 response in IgG4-RD represents a generalised polyclonal amplification by examining the response to common environmental antigens.

Methods

Serum from 24 patients with IgG4-RD (14 treatment-naive, 10 treatment-experienced), 9 patients with primary sclerosing cholangitis and an elevated serum IgG4 (PSC-high IgG4), and 18 healthy controls were tested against egg white and yolk, milk, banana, cat, peanut, rice and wheat antigens by radioimmunoassay.

Results

We demonstrated an elevated polyclonal IgG4 response to multiple antigens in patients with IgG4-RD and in PSC-high IgG4, compared with healthy controls. There was a strong correlation between serum IgG4 and antigen-specific responses. Responses to antigens were higher in treatment-naive compared with treatment-experienced patients with IgG4-RD. Serum electrophoresis and immunofixation demonstrated polyclonality.

Conclusions

This is the first study to show enhanced levels of polyclonal IgG4 to multiple antigens in IgG4-RD. This supports that elevated IgG4 levels reflect an aberrant immunological regulation of the overall IgG4 response, but does not exclude that causality of disease could be antigen-driven.

Historic overview of allergy research in the Netherlands

Research in allergy has a long history in the Netherlands, although the relation with immunology has not always been appreciated. In many aspects Dutch researchers have made major contribution in allergy research. This ranges from the first characterization of house dust mite as an important allergen, the first characterization of human Th2 and Th1 T cell clones, to the development of diagnostic test systems. In this overview Aalberse and Knol have made an overview of the major contributions of Dutch immunologists in allergy.

B-cell depletion attenuates serological biomarkers of fibrosis and myofibroblast activation in IgG4-related disease

OBJECTIVES

Fibrosis is a predominant feature of IgG4-related disease (IgG4-RD). B-cell depletion induces a prompt clinical and immunological response in patients with IgG4-RD, but the effects of this intervention on fibrosis in IgG4-RD are unknown. We used the enhanced liver fibrosis (ELF) score to address the impact of rituximab on fibroblast activation. The ELF score is an algorithm based on serum concentrations of procollagen-III aminoterminal propeptide, tissue inhibitor of matrix metalloproteinase-1 and hyaluronic acid.

METHODS

Ten patients with active, untreated IgG4-RD were enrolled. ELF scores were measured and correlated with the IgG4-RD Responder Index, serum IgG4, circulating plasmablasts and imaging studies. Through immunohistochemical stains for CD3, CD20, IgG4 and α-smooth muscle actin, we assessed the extent of the lymphoplasmacytic infiltration and the degree of fibroblast activation in one patient with tissue biopsies before and after rituximab.

RESULTS

The ELF score was increased in patients with IgG4-RD compared with healthy controls (8.3±1.4 vs 6.2±0.9; p=0.002) and correlated with the number of organs involved (R(2)=0.41; p=0.04). Rituximab induced significant reductions in the ELF score, the number of circulating plasmablasts and the IgG4-RD Responder Index (p<0.05 for all three parameters). Rituximab reduced both the lymphoplasmacytic infiltrate and myofibroblast activation. IgG4-RD relapse coincided with recurrent increases in the ELF score, indicating reactivation of collagen deposition.

CONCLUSIONS

The ELF score may be a clinically useful indicator of active fibrosis and the extent of disease in IgG4-RD. B-cell depletion has the potential to halt continued collagen deposition by attenuating the secretory phenotype of myofibroblasts in IgG4-RD lesions.

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.

IgG4-related disease with atypical laryngeal presentation and Behçet/granulomatous polyangiitis mimicking features

The following report describes two male patients with an ongoing medical history with a predominant laryngeal focus, who were finally diagnosed with IgG4-related disease (IgG4-RD). Their primary symptoms included hoarseness and pain of the throat, and they had undergone multiple laryngeal surgeries and laser treatments due to tumorous growth with limited success. Due to the onset of additional symptoms, they initially received the diagnoses granulomatous polyangiitis (GPA) and Behçet's disease. However, further analysis showed elevated IgG4 levels in serum and infiltration of IgG4-positive plasma cells upon biopsy of laryngeal and pulmonary tissue. Treatment was started with moderate doses of prednisone, leading to a rapid resolution of symptoms.

Immunoglobulin G4+ clones identified by next-generation sequencing dominate the B cell receptor repertoire in immunoglobulin G4 associated cholangitis

Immunoglobulin G4 (IgG4)-associated cholangitis (IAC) is a manifestation of the recently discovered idiopathic IgG4-related disease. The majority of patients have elevated serum IgG4 levels and/or IgG4-positive B-cell and plasma cell infiltrates in the affected tissue. We hypothesized that clonally expanded, class-switched IgG4-positive B cells and plasma cells could be causal to these poorly understood phenomena. In a prospective cohort of six consecutive IAC patients, six healthy controls, and six disease controls, we used a novel next-generation sequencing approach to screen the B-cell receptor (BCR) repertoires, in blood as well as in affected tissue, for IgG4+ clones. A full repertoire analysis of the BCR heavy chain was performed using GS-FLX/454 and customized bioinformatics algorithms (>10,000 sequences/sample; clones with a frequency ≥0.5% were considered dominant). We found that the most dominant clones within the IgG+ BCRheavy repertoire of the peripheral blood at baseline were IgG4+ only in IAC patients. In all IAC patients, but none of the controls, IgG4+ BCR clones were among the 10 most dominant BCR clones of any immunoglobulin isotype (IgA, IgD, IgM, and IgG) in blood. The BCR repertoires of the duodenal papilla comprised the same dominant IgG4+ clones as the paired peripheral blood samples. In all IAC patients, after 4 and 8 weeks of corticosteroid therapy the contribution of these IgG4+ clones to the IgG+ repertoire as well as to total BCR repertoire was marginalized, mirroring sharp declines in serum IgG4 titers and regression of clinical symptoms.

CONCLUSION

The novel finding of highly abundant IgG4+ BCR clones in blood and tissue of patients with active IAC, which disappear upon corticosteroid treatment, suggests that specific B cell responses are pivotal to the pathogenesis of IAC. (HEPATOLOGY 2013 ).

Hepatic sarcoidosis with an increased serum level of immunoglobulin G4

A 70-year-old woman with an increased uptake of 18-Fluorodeoxyglucose (FDG) in whole liver on positron emission tomography (PET) was referred to our hospital. Laboratory examinations showed increased serum levels of total immunoglobulin G (IgG) and IgG4. Gallium scintigraphy showed a remarkable uptake in the liver but not in any other organs. On computed tomography (CT) and magnetic resonance imaging (MRI), multiple foci of abnormal density were observed in the liver, but the pancreas and bile duct lacked any indications of IgG4-related sclerosing disease. A liver biopsy specimen revealed multiple non-necrotizing granulomas. This is the first report of hepatic sarocidosis in a patient with an elevated serum level of IgG4.