Mechanisms and assessment of IgG4-related disease: lessons for the rheumatologist. Nat Rev Rheumatol. 2014;10:148-159. [PMID: 24296677 DOI: 10.1038/nrrheum.2013.183]

IgG4-related disease mimicking a liver abscess

IgG4-related disease (IGRD) is a complex medical condition affecting multiple organs, including the liver. The condition is characterized by excessive production of IgG4 antibodies, leading to chronic inflammation and tissue damage. We present a case of a 37-year-old man with a history of chronic pancreatitis was diagnosed with a liver mass. Initial treatment included piperacillin and tazobactam, but the patient's condition worsened. An ultrasound-guided biopsy revealed increased IgG4 positive cells, leading to the diagnosis of an inflammatory pseudotumor associated with IGRD. The patient was treated with prednisone taper therapy, and the liver mass resolved after six months of corticoid treatment.

A Case of IgG4-Related Disease Manifesting as Extensive Abdominal Periarteritis and Membranous Nephropathy, Successfully Controlled with Low-Dose Steroid Therapy without Relapse or Complications

INTRODUCTION

IgG4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disease that can affect nearly every organ system, including blood vessels and the kidney. IgG4-related vascular lesions mainly involve the aorta, and the dominant renal manifestation is tubulointerstitial nephritis (TIN). Here, we report a case of IgG4-RD demonstrating extensive abdominal periarteritis and membranous nephropathy (MN).

CASE PRESENTATION

The patient was a 71-year-old man with peptic ulcer who developed nephrotic syndrome, with a low serum albumin level (1.8 g/dL), massive urinary protein (6.1 g/day), and high serum IgG4 level (435 mg/dL). Computed tomography images revealed soft tissue mass around the medium-sized abdominal arteries. Renal pathological findings showed MN and focal infiltration of numerous IgG4-positive cells in the interstitium. The findings of high serum IgG4 levels, periarteritis, and focal inflammation with rich IgG4-positive plasma cells led to the diagnosis of IgG4-RD. We chose low-dose steroid therapy to prevent the recurrence of the peptic ulcer and aneurysm formation in the affected arteries, which can occur with medium to high doses of prednisolone. We successfully controlled IgG4-related periarteritis and kidney disease without relapse or complications.

CONCLUSION

The varied clinical manifestations of IgG4-RD sometimes make the diagnosis challenging. However, clinicians should diagnose IgG4-RD based on serological, radiological, and pathological evaluations because, without appropriate therapy, IgG4-RD can lead to irreversible organ failure caused by swelling, obstruction, or fibrosis of the organs.

Overlap syndromes in sarcoidosis: Unveiling the masquerader

As a multi system granulomatous disease, clinical presentations of sarcoidosis are highly variable. In the absence of a stereotypical clinical presentation such as asymptomatic bilateral hilar adenopathy, Lofgren's syndrome, or lupus pernio, a diagnosis of sarcoidosis typically requires 1) compatible clinical presentation, 2) histologic evidence of granulomatous inflammation, and 3) the exclusion of other causes. The clinical presentation of sarcoidosis is often nonspecific and a variety of other causes of granulomatous inflammation can make diagnosing sarcoidosis a challenge for clinicians. "Overlap syndromes" are often used to describe clinical presentations of sarcoidosis that share histologic and clinical features of other diseases, or when the diagnosis of sarcoidosis is made in association with the coexistence of another diagnosis with similar clinical or histologic findings. Because of the risk of diagnostic delay and diagnostic errors, it is vital for clinicians to be familiar with overlap syndromes in sarcoidosis. The coexistence of sarcoidosis with other diseases can also significantly impact disease management and outcomes. This article will review the most current published data on overlap syndromes in sarcoidosis to aid clinicians in diagnosing and managing these complex patients.

Renal Manifestations of IgG4-Related Disease: A Concise Review

IgG4-related disease (IgG4-RD) is an immune-mediated disorder marked by fibro-inflammatory masses that can infiltrate multiple organ systems. Due to its relatively recent discovery and limited understanding of its pathophysiology, IgG4-related disease may be difficult to recognize and is consequently potentially underdiagnosed. Renal involvement is becoming regarded as one of the key features of this disease. To date, the most well-recognized renal complication of IgG4-related disease is tubulointerstitial nephritis, but membranous glomerulonephritis, renal masses, and retroperitoneal fibrosis have also been reported. This concise review has two objectives. First, it will briefly encapsulate the history, epidemiology, and presentation of IgG4-related disease. Second, it will examine the reported renal manifestations of IgG4-related disease, exploring the relevant histology, imaging, clinical features, and treatment considerations. This synthesis will be highly relevant for nephrologists, rheumatologists, general internists, and renal pathologists to raise awareness and help improve early recognition of IgG4-related kidney disease (IgG4-RKD).

New insights into chronic rhinosinusitis associated with IgG4-related disease

IgG4-related disease (IgG4-RD) is a chronic inflammatory disorder characterized by elevated IgG4 serum levels, abundant IgG4-positive plasmacyte infiltration, and fibrosis of various organs, including the head and neck. We aimed to provide an overall review of IgG4-RD in the sinonasal region and propose a novel entity and criteria of chronic rhinosinusitis (CRS) associated with IgG4-RD as "IgG4-CRS," a distinct manifestation of IgG4-RD in the sinonasal region. Sinonasal involvement has been increasingly recognized; however, this region is not included in the classic IgG4-RD-affected organs. The clinical features of IgG4-CRS, including its prevalence and relationship with allergies and olfactory disturbances, have also been explored. Serum IgG4 levels and IgG4-positive plasma cell infiltrations, crucial diagnostic factors, have been discussed in association with IgG4-CRS pathogenesis. Fibrosis, a hallmark of IgG4-RD, is observed in sinonasal tissues; however, typical fibrosis, such as storiform fibrosis, is not usually found. Mimics or complications in eosinophilic CRS (ECRS) and antineutrophil cytoplasmic antibody-associated vasculitis (AAV) are highlighted. Treatment often involves typically effective glucocorticoids. Organ-specific diagnostic criteria for the sinonasal region have not currently been established. Hence, this review aims to foster awareness and understanding of IgG4-CRS among ENT physicians and to provide a basis for future research and diagnostic refinement.

Cardiac Tamponade as an Initial Manifestation of Diffuse Large B-cell Lymphoma One Year after IgG4-related Disease in Remission

A 65-year-old man with multiple lymphadenopathies was diagnosed with IgG4-related disease (IgG4-RD) based on findings of a cervical lymph node biopsy and an elevated serum IgG4 level. Treatment was initiated after the onset of autoimmune pancreatitis, and he achieved remission. He developed diffuse large B-cell lymphoma one year later. Pericardial involvement of lymphoma resulted in cardiac tamponade, and he died before histopathological confirmation of lymphoma was made due to a lethal arrhythmia caused by massive involvement of lymphoma into the myocardium. Because patients with IgG4-RD might have an increased risk of malignant diseases, including lymphoma, histopathological examinations should be considered at any time during the course of IgG4-RD.

Analysis of the saliva microbiome in patients with immunoglobulin G4-related disease

OBJECTIVES

This article aims to investigate the saliva microbiome in patients with immunoglobulin G4-related disease (IgG4RD) compared with primary Sjögren's syndrome (SS).

METHODS

Saliva samples were collected from 11 IgG4RD and 11 SS patients who visited IMSUT Hospital, The Institute of Medical Science, The University of Tokyo. Deoxyribonucleic acid (DNA) was extracted from the samples, and primers were used to amplify the V3-V4 regions of bacterial and archaeal 16S ribosomal RNA (rRNA) genes, which was then analysed by paired-end sequencing. Amplicon reads were processed using QIIME2 to generate representative sequences. The Greengenes database was used to identify the bacterial flora in each sample and compare them between groups.

RESULTS

The IgG4RD and SS groups exhibited differences in bacterial diversity. Cluster analyses of attributed classification groups by species and disease showed that IgG4RD and SS cases formed individual clusters. Significant differences in relative abundance between IgG4RD and SS were observed for the following organisms: Mogibacterium (P = .0051), Solobacterium moorei (P = .0195), Slackia (P = .0356), and Moryella (P = .0455).

CONCLUSIONS

Salivary microbiome analysis of IgG4RD and SS patients revealed significantly higher relative proportions of Mogibacterium, S. moorei, Slackia, and Moryella bacteria in IgG4RD compared with SS.

Autoimmune Polyglandular Syndrome Type 3 Complicated with IgG4-related Disease

A 52-year-old Japanese woman developed type 1 diabetes mellitus (type 1 DM) at 41 years old. She became complicated with Hashimoto's disease and showed swelling of both submandibular glands, which was diagnosed as IgG4-related disease (IgG4-RD). This is a rare case of a Japanese patient with autoimmune polyglandular syndrome type 3A (APS-3A) coexisting with autoimmune thyroid disease (AITD) and type 1 DM complicated by IgG4-RD. Bilateral submandibular gland resection was successfully performed without steroid therapy. We discuss the possibility that the immunological pathogenic mechanisms of APS-3A and IgG4-RD are related.

HLA-DRB1 Is Associated with Therapeutic Responsiveness in IgG4-related Disease

Objective Glucocorticoids are key drugs used in remission induction therapy for IgG4-related disease (IgG4-RD). However, the therapeutic outcomes vary widely, with some patients requiring long-term maintenance therapy and others relapsing repeatedly, whereas still others can tolerate withdrawal. These variations underscore the need for personalized treatment strategies for IgG4-RD. We examined the relationship between human leukocyte antigen (HLA) genotypes and the response to glucocorticoid treatment in patients with IgG4-RD. Methods Eighteen IgG4-RD patients visiting our hospital were included in the study. Peripheral blood samples were collected, HLA genotypes were determined, and the response to glucocorticoid treatment (maintenance dose at the time of last observation, glucocorticoid dose when the serum IgG4 level was the lowest after remission induction therapy, and occurrence of relapse) was examined retrospectively. Results The DQB1*12:01 genotypes were associated with a prednisolone maintenance dose of <7 mg/day. A prednisolone dose ≥10 mg with a minimum serum IgG4 level was significantly more common in B*40:01 and DRB1-GB-7-Val (DRB1*04:01, *04:03, *04:05, *04:06, and *04:10) patients than other alleles. Relapse also tended to be more common in DRB1-GB-7-Val carriers than other alleles. Conclusion These data suggest that HLA-DRB1 is associated with glucocorticoid treatment responsiveness and is important for follow-up monitoring of serum IgG4 levels during glucocorticoid tapering. We believe that these data will contribute to the future development of personalized medicine for IgG4-RD.

Imbalance of Th1 and Th2 Cytokines and Stem Cell Therapy in Pathological Pain

The pathophysiological importance of T helper 1 (Th1) and Th2 cell cytokines in pathological pain has been highly debated in recent decades. However, the analgesic strategy targeting individual cytokines still has a long way to go for clinical application. In this review, we focus on the contributions of Th1 cytokines (TNF-α, IFN-γ, and IL-2) and Th2 cytokines (IL-4, IL-5, IL-10, and IL-13) in rodent pain models and human pain-related diseases. A large number of studies have shown that Th1 and Th2 cytokines have opposing effects on pain modulation. The imbalance of Th1 and Th2 cytokines might determine the final effect of pain generation or inhibition. However, increasing evidence indicates that targeting the individual cytokine is not sufficient for the treatment of pathological pain. It is practical to suggest a promising therapeutic strategy against the combined effects of Th1 and Th2 cytokines. We summarize the current advances in stem cell therapy for pain-related diseases. Preclinical and clinical studies show that stem cells inhibit proinflammatory cytokines and release enormous Th2 cytokines that exhibit a strong analgesic effect. Therefore, a shift of the imbalance of Th1 and Th2 cytokines induced by stem cells will provide a novel therapeutic strategy against intractable pain. It is extremely important to reveal the cellular and molecular mechanisms of stem cell-mediated analgesia. The efficiency and safety of stem cell therapy should be carefully evaluated in animal models and patients with pathological pain.

Lysosome-Associated Membrane Protein 3 Induces Lysosome-Dependent Cell Death by Impairing Autophagic Caspase 8 Degradation in the Salivary Glands of Individuals With Sjögren's Disease

OBJECTIVE

Lysosome-associated membrane protein 3 (LAMP3) overexpression is implicated in the development and progression of Sjögren's disease (SjD) by inducing lysosomal membrane permeabilization (LMP) and apoptotic cell death in salivary gland epithelium. The aim of this study was to clarify the molecular details of LAMP3-induced lysosome-dependent cell death and to test lysosomal biogenesis as a therapeutic intervention.

METHODS

Human labial minor salivary gland biopsies were analyzed using immunofluorescence staining for LAMP3 expression levels and galectin-3 puncta formation, a marker of LMP. Expression level of caspase 8, an initiator of LMP, was determined by Western blotting in cell culture. Galectin-3 puncta formation and apoptosis were evaluated in cell cultures and a mouse model treated with glucagon-like peptide 1 receptor (GLP-1R) agonists, a known promoter of lysosomal biogenesis.

RESULTS

Galectin-3 puncta formation was more frequent in the salivary glands of SjD patients compared to control glands. The proportion of galectin-3 puncta-positive cells was positively correlated with LAMP3 expression levels in the glands. LAMP3 overexpression increased caspase 8 expression, and knockdown of caspase 8 decreased galectin-3 puncta formation and apoptosis in LAMP3-overexpressing cells. Inhibition of autophagy increased caspase 8 expression, while restoration of lysosomal function using GLP-1R agonists decreased caspase 8 expression, which reduced galectin-3 puncta formation and apoptosis in both LAMP3-overexpressing cells and mice.

CONCLUSION

LAMP3 overexpression induced lysosomal dysfunction, resulting in lysosome-dependent cell death via impaired autophagic caspase 8 degradation, and restoring lysosomal function using GLP-1R agonists could prevent this. These findings suggested that LAMP3-induced lysosomal dysfunction is central to disease development and is a target for therapeutic intervention in SjD.

Identification of risk factors for elevated serum IgG4 levels in subjects in a large-scale health checkup cohort study

Introduction

To allow the identification of IgG4-related disease (IgG4-RD) from a subclinical phase as it is important to understand the risk of elevated serum IgG4 levels. We planned to evaluate serum IgG4 levels in the participants of the Nagasaki Islands Study (NaIS), a large-scale health checkup cohort study.

Methods

This study included 3,240 individuals who participated in the NaIS between 2016 and 2018 and consented to participate in the study. Serum IgG4, IgG, and IgE levels and human leukocyte antigen (HLA) genotyping results of the NaIS subjects as well as lifestyle habits and peripheral blood test results were analyzed. The magnetic bead panel assay (MBA) and the standard nephelometry immunoassay (NIA) were used to measure serum IgG4 levels. The data were evaluated using multivariate analysis to identify lifestyle and genetic factors associated with elevated serum IgG4 levels.

Results

Serum IgG4 levels measured with the NIA and MBA showed a tight positive correlation between the two groups (correlation coefficient 0.942). The median age of the participants in the NaIS was 69 years [63-77]. The median serum IgG4 level was 30.2 mg/dL [IQR 12.5-59.8]. Overall, 1019 (32.1%) patients had a history of smoking. When the subjects were stratified into three groups based on the smoking intensity (pack-year), the serum IgG4 level was significantly higher among those with a higher smoking intensity. Accordingly, the multivariate analysis identified a significant relationship between smoking status and serum IgG4 elevation.

Conclusion

In this study, smoking was identified as a lifestyle factor correlating positively with elevated serum IgG4 levels.

IgG4-related Disease Emerging after COVID-19 mRNA Vaccination: A Case Report

A 78-year-old Japanese woman with no history of rheumatic disease received 2 doses of the BNT162b2 COVID-19 mRNA vaccine. Two weeks later, she noticed bilateral swelling in the submandibular region. Blood tests showed hyper-immunoglobulin (Ig)G4emia, and ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) revealed the strong accumulation of FDG in the enlarged pancreas. She was diagnosed with IgG4-related disease (IgG4-RD) according to the American College of Rheumatology (ACR)/the European League Against Rheumatism (EULAR) classification criteria. Treatment was started with prednisolone at 30 mg/day, and the organ enlargement improved. We herein report a case of IgG4-RD that may have been associated with an mRNA vaccine.

IgG4 related pericardium and lung disease in pediatric patient complicated with fatal massive hemoptysis: a case report and review of literature

BACKGROUND

IgG4-related disease (IgG4-RD) is a progressive and sometimes fatal disease that rarely affects pediatric age group. It may affect the orbits, lacrimal and salivary glands, pancreas, kidneys, peritoneum and other organs. Lung and pleura are not commonly reported in IgG4-RD. We here present a rare case of pediatric IgG4-RD with rare involvement of pericardium, pleura and lungs.

CASE PRESENTATION

A 13-year-old girl presented with intrathoracic IgG4-RD with pleuropericardial involvement. She showed initial improvement on prednisolone. Azathioprine and then mycophenolate failed to control relapses during steroid tapering. Her last relapse was treated by rituximab however, the patient developed acute fatal massive hemoptysis.

CONCLUSIONS

Pediatric IgG4-RD is a rare entity with pericardio-pulmonary affection as the rare of the rare. Usual treatment of prednisolone and steroid sparing agents should be used, with rituximab used as a rescue therapy, but fatal complications may occur.

Differentiation between IgG4-related Mikulicz disease and Sjögren's syndrome: A review case report and literature review

RATIONALE

IgG4-related diseases cause lesions in various organs throughout the body. In otorhinolaryngology, IgG4-related Mikulicz's disease is suspected and diagnosed based on the presence of lesions of the head and neck, salivary and lacrimal gland enlargement, and bilateral sinus opacity concentrated on the maxillary sinuses. However, in some cases, it is necessary to consider about differentiation between IgG4-related Mikulicz's disease and Sjögren syndrome.

PATIENT CONCERNS AND DIAGNOSIS

A 75-years-old male patient visited our hospital with bilateral otitis media with effusion, which was resistant to conservative treatment. Other symptoms at presentation included enlarged bilateral submandibular and sublingual glands marked oral dryness, severe decrease in saliva secretion (1 mL/10 minutes), and dry eyes. We conducted a Schirmer's and fluorescent dye tests, both of which were positive. High serum IgG4 levels were observed, and although the Sjögren syndrome (SS)-A/SS-B antibodies were negative, marked hypolacrimation and tear secretion were observed. Therefore, a detailed examination considering both IgG4-related Mikulicz's disease and SS was conducted. Salivary gland scintigraphy performed prior to the salivary gland biopsy revealed a marked decrease in uptake, which satisfied the diagnostic criteria for SS; however, it was difficult to diagnose IgG4-related disease based on the diagnostic definition.

INTERVENSIONS

Although a definitive diagnosis of SS was made, the persistent otitis media with effusion that was resistant to conservative treatment and bilateral mixed hearing loss were confirmed. As mixed hearing loss is considered an otological symptom of IgG4-related disease, oral steroid treatment was administered.

OUTCOME

Thereafter, marked recovery of hearing and reduced swelling and induration of the bilateral parotid and submandibular glands were observed. Clinically, IgG4-related Mikulicz's disease was strongly suspected, but a definite diagnosis of SS was made.

LESSONS

In the absence of an IgG4-related Mikulicz's disease diagnosis, careful differentiation between IgG4-related Mikulicz's disease and 2 diseases and their diagnostic criteria was essential.

New biomarkers for the diagnosis of pleural effusion

Background

Persistent undiagnosed effusion is present in approximately 15% of all causes of exudative effusion. Pleural effusion caused by immunoglobulin G4 (IgG4) is a new type of pleural effusion. Tumor markers such as Carcinoembryonic antigen (CEA) may play a role in the diagnosis of malignant pleural effusion. This study aimed to evaluate the use of serum Immunoglobulin G4 and carcinoembryonic antigen in diagnosing pleural effusion.

Methods

This observational descriptive cross-sectional study comprised 89 individuals with exudative pleural effusion who visited the Assiut university hospital's chest department. All patients were examined and asked about their medical history. Also, chest X-ray, MSCT chest, transthoracic ultrasonography, pleural fluid analysis and cytology, serum level of carcinoembryonic antigen, and immunoglobulin G4 were performed. In addition, pleural biopsy, bronchoscopy, and thoracoscopy were performed when required.

Results

In comparison to another diagnosis, the level of serum IgG 4 was observed to be substantially greater in individuals with IgG4-associated effusion (725± 225.45). Patients with malignant mesothelioma (70± 16.24) and metastatic adenocarcinoma (93.52± 19.34) had lower levels of IgG4. In contrast, the serum level of CEA was significantly higher in individuals with malignant mesothelioma (79.50± 29.47) and metastatic adenocarcinoma (68.71± 28.98). Patients with para-pneumonic effusion had a minor serum level of CEA (0.36 ± 0.26). At cutoff point > 152 mg/dl serum IgG-4 had 100% sensitivity and 94% specificity in the diagnosis of IgG4 related pleural effusion with an overall accuracy of 95.3% and area under the curve of 0.97. At the cutoff point > 5 ng/ml serum CEA had 77% sensitivity and 100% specificity in diagnosing malignant pleural effusion with an overall accuracy of 91.1% and area under the curve of 0.88.

Conclusion

Serum IgG4 higher than 152 mg/dl has good diagnostic accuracy in cases of undiagnosed pleural effusion. Carcinoembryonic antigen aids in diagnosing malignant pleural effusion with a cutoff point higher than 5 ng/ml in serum.

Trial registration

ClinicalTrials.gov registration ID NCT03260088

Idiopathic Multicentric Castleman Disease with Strikingly Elevated IgG4 Concentration in the Serum and Abundant IgG4-Positive Cells in the Tissue: A Case Report

Idiopathic multicentric Castleman disease (iMCD) can be challenging to distinguish clinically and histopathologically from Immunoglobulin G4-related disease (IgG4RD). A 73-year-old man was referred to a rheumatologist for suspected autoimmune-related polyclonal hypergammaglobulinemia. The patient had a history of multiple lymphadenopathies in the neck for over 20 years. Laboratory data showed elevated serum immunoglobulin G4 (IgG4) levels, hypergammaglobulinemia, high C-reactive protein (CRP) levels, marked anemia, and positivity for several autoantibodies. Additionally, imaging studies revealed multiple enlarged lymph nodes and multifocal, ill-defined, small patchy opacities over the lung. Biopsies of the neck lymph node and right lung revealed typical features of multicentric Castleman disease (MCD). Immunohistochemical staining was negative for human herpesvirus-8 (HHV-8) in both lymph nodes and the right lung, sub-classified as iMCD, whereas the IgG4/IgG ratio was >40%, which raised the suspicion of IgG4RD. However, serological cytokine analysis demonstrated an increased interleukin-6 (IL-6) level, alongside systemic inflammatory and histopathological features, distinguishing MCD from IgG4RD in this patient. The patient was treated with short-term glucocorticoids and regular infusion of an anti-IL-6 receptor monoclonal antibody (tocilizumab), with satisfactory clinical and radiographic responses. Notably, differentiating MCD from IgG4RD is crucial for optimal treatment. Clinical and pathological features may assist in distinguishing between these two diseases.

CD4+CD8+ T follicular helper cells regulate humoral immunity in chronic inflammatory lesions

T follicular helper (Tfh) cells drive humoral immunity by facilitating B cell responses at the initial and recall phases. Recent studies have indicated the possible involvement of Tfh cells in the process of chronic inflammation. However, the functional role of Tfh cells in persistent immune settings remains unclear. Here, we report that CD4⁺CD8⁺ (double-positive, DP; CD3⁺CD4⁺CD8⁺CXCR5^hiPD-1^hi) Tfh cells, a subset of germinal-center-type Tfh cells, were abundantly present in the fibroinflammatory lesions of patients with immunoglobulin G4-related disease (IgG4-RD). Transcriptome analyses showed that these DP-Tfh cells in the lesions of IgG4-RD preferentially expressed signature genes characteristic of cytotoxic CD8⁺ T cells, such as Eomes, CRTAM, GPR56, and granzymes, in addition to CD70. Scatter diagram analyses to examine the relationships between tissue-resident lymphocytes and various clinical parameters revealed that the levels of DP-Tfh cells were inversely correlated to the levels of serum IgG4 and local IgG4-expressing (IgG4⁺) memory B cells (CD19⁺CD27⁺IgD^-) in patients with IgG4-RD. Cell culture experiments using autologous tonsillar lymphocytes further suggested that DP-Tfh cells possess a poor B-cell helper function and instead regulate memory B cells. Since CD4⁺ (single positive, SP; CD3⁺CD4⁺CD8^-CXCR5^hiPD-1^hi) Tfh cells differentiated into DP-Tfh cells under stimulation with IL-2 and IL-7 as assessed by in vitro experiments, these data imply that SP-Tfh cells are a possible origin of DP-Tfh cells under persistent inflammation. These findings highlight the potential feedback loop mechanism of Tfh cells in immune tolerance under chronic inflammatory conditions. Further studies on DP-Tfh cells may facilitate control of unresolved humoral responses in IgG4-RD pathological inflammation.

T Cell Roles and Activity in Chronic Sclerosing Sialadenitis as IgG4-Related Disease: Current Concepts in Immunopathogenesis

IgG4-related disease is a multiorgan immunological fibroinflammatory disorder characterized by lymphoplasmacytic infiltration and fibrosis in multiple organs accompanied by high serum IgG4 levels. The salivary glands are the most common organs involved in this disease. Recently, chronic sclerosing sialadenitis affecting salivary glands, formerly known as Küttner's tumor, and Mikulicz's disease have been classified as a class of IgG4-related diseases. The etiopathobiology of IgG4-related disease is not fully understood. It has recently been hypothesized that the inflammatory and fibrotic process and the increased serum IgG4⁺ levels in IgG4-related disease are the result of an interaction between B cells and T helper cells, suggesting that T cells may play a key role in the pathogenesis of this disease. The aim of this review is to discuss the proposed roles of different T cell subsets in the pathogenesis of IgG4-related disease focusing on their roles in immunopathogenesis of IgG4-related sialadenitis.

The differential diagnosis of IgG4-related disease based on machine learning

INTRODUCTION

To eliminate the disparity and maldistribution of physicians and medical specialty services, the development of diagnostic support for rare diseases using artificial intelligence is being promoted. Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a rare disorder often requiring special knowledge and experience to diagnose. In this study, we investigated the possibility of differential diagnosis of IgG4-RD based on basic patient characteristics and blood test findings using machine learning.

METHODS

Six hundred and two patients with IgG4-RD and 204 patients with non-IgG4-RD that needed to be differentiated who visited the participating institutions were included in the study. Ten percent of the subjects were randomly excluded as a validation sample. Among the remaining cases, 80% were used as training samples, and the remaining 20% were used as test samples. Finally, validation was performed on the validation sample. The analysis was performed using a decision tree and a random forest model. Furthermore, a comparison was made between conditions with and without the serum IgG4 concentration. Accuracy was evaluated using the area under the receiver-operating characteristic (AUROC) curve.

RESULTS

In diagnosing IgG4-RD, the AUROC curve values of the decision tree and the random forest method were 0.906 and 0.974, respectively, when serum IgG4 levels were included in the analysis. Excluding serum IgG4 levels, the AUROC curve value of the analysis by the random forest method was 0.925.

CONCLUSION

Based on machine learning in a multicenter collaboration, with or without serum IgG4 data, basic patient characteristics and blood test findings alone were sufficient to differentiate IgG4-RD from non-IgG4-RD.

IgG4-Related Disease: A Clinical Case Series From a Tertiary Care Center in India

AIM

Immunoglobulin G4-related disease (IgG4-RD) is often an unrecognized, rare fibroinflammatory condition that can involve various organ systems. This study aimed to identify the different clinical patterns of this disease in a single center in North India.

METHODS

Patients were diagnosed on the basis of published diagnostic criteria for IgG4-RD. Patients' presenting complaints; epidemiologic profiles; and laboratory, radiologic, and histologic findings along with the treatment and outcomes were collected and analyzed.

RESULTS

In total, 70 patients were diagnosed with the disease. The female-to-male ratio was 0.94:1, and it increased with multiorgan involvement. The mean age of patients was 41.4 years, and the majority of the patients (65.7%) were younger than 50 years. Patients were diagnosed as possible (38.57%), probable (32.85%), and definite (28.57%) IgG4-RD. The incidence of the involvement of orbital and periorbital tissues was the highest (52.9%); however, 13% of the patients had multiple organ involvement. Patients with involvement of the retroperitoneal tissues and the lymph nodes were 8.5% and 5.7%, respectively. Increased serum IgG4 levels were found in 74.3% of the patients with single-organ involvement, whereas all patients with multiorgan involvement had increased IgG4 levels. The majority of patients (94.3%) required immunosuppressive medications along with corticosteroids. Azathioprine was the most commonly used (72.8%) immunosuppressive medication. Rituximab was used in 17.1% of the patients, of whom only one had multisystem involvement.

CONCLUSIONS

This study depicts the most common patterns of organ involvement, along with the epidemiologic, laboratory, histologic, and radiologic data and response to treatment, in IgG4-RD, with a definite ophthalmology referral bias.

Two cases of immunoglobulin G4-related disease diagnosed by transvaginal urethral needle biopsy

INTRODUCTION

Immunoglobulin G4-related disease is a systemic disease characterized by multifocal systemic involvement. We report two cases of women diagnosed with immunoglobulin G4-related disease in the urethra.

CASE PRESENTATION

Case 1: A 67-year-old woman presented with discomfort around her perineum. Magnetic resonance imaging revealed a well-defined mass around the urethra. She underwent an ultrasound-guided core needle biopsy of the mass. The pathologic specimen showed immunoglobulin G4 positive cells. Steroid therapy was initiated, causing improvement of symptoms, decreased serum immunoglobulin G4 levels, and shrinking of the mass. Case 2: An 89-year-old woman was accidentally diagnosed with renal pelvic wall thickening on computed tomography. The pathologic specimen captured by ultrasound-guided needle biopsy showed immunoglobulin G4 positive cells. She had no symptoms and received no medical treatment.

CONCLUSION

The frequency of urethral mass formation in female patients with immunoglobulin G4-related disease may also be high, and an echo-guided transvaginal urethral biopsy may be performed as a definitive diagnostic tool for immunoglobulin G4-related disease.

Pathogenic roles and therapeutic potential of the CCL8-CCR8 axis in a murine model of IgG4-related sialadenitis

BACKGROUND

Our previous studies reveal that CCL18-CCR8 chemokine axis is upregulated in patients of immunoglobulin G4-related disease (IgG4-RD), suggesting that the CCL18-CCR8 axis is implicated in the etiology of IgG4-RD, although whether this axis has a potential as a therapeutic target remains unclear. Our purpose was to clarify the pathogenic roles and therapeutic potential of the murine CCL8 (analog of human CCL18)-CCR8 axis by using an animal model of IgG4-RD (LAT Y136F knockin mice; LAT mice).

METHODS

We compared the infiltration of inflammatory cells and the fibrosis of the salivary glands of 6-week-old LAT mice and littermate mice. The expressions of Ccl8 and Ccr8 were also compared. Next, we investigated the therapeutic effects of intravenous administration of anti-CCL8 neutralizing antibody in LAT mice against inflammation and fibrosis of the salivary glands. We also investigated the effects of stimulation with recombinant mouse CCL8 on the collagen production in a mouse fibroblast cell line (NIH/3 T3) in vitro.

RESULTS

When compared with the littermates, the LAT mice showed apparent infiltration of inflammatory cells and fibrosis in the salivary glands. The focus and fibrosis score in the salivary glands were significantly higher in the LAT mice than in the littermates. The expression levels of Ccl8 in the spleen and of Ccr8 in the salivary glands were significantly higher in the LAT mice than in the littermates. Anti-CCL8 antibody significantly improved the focus and fibrosis score in the salivary glands of the LAT mice. In vitro, stimulation with recombinant mouse CCL8 significantly increased the expression of collagen and ERK1/2 phosphorylation in NIH/3 T3.

CONCLUSION

We clarified the overexpression and therapeutic potential of the mouse CCL8-CCR8 axis in LAT mice, which could play a crucial role in fibrosis via ERK1/2 phosphorylation, as well as the chemotaxis of inflammatory cells. The human CCL18-CCR8 axis might be a novel therapeutic target for IgG4-RD.

Inflammatory pseudotumor of Castleman disease and IgG4-related disease masquerading as kidney malignancy

Background

With widespread clinical application of imaging techniques, renal space-occupying lesions have been identified at an increasing frequency. Here, we report two rare cases, Castleman disease (CD) and IgG4-related disease (IgG4-RD), presenting primarily with the symptoms and imaging findings of kidney malignancy.

Case presentation

In case 1, an occupying lesion located in the right renal pelvis was detected using magnetic resonance imaging in a 32-year-old female who presented with hematuria and lumbago. First misdiagnosed as carcinoma of the renal pelvis, the patient underwent right radical nephroureterectomy. However, postoperative pathological and immunohistochemistry studies finally confirmed the diagnosis of CD. In case 2, a 45-year-old male presented with the chief complaint of anuria. Nephrostomy and renal biopsy indicated lymphoma, following which, antegrade urography and computed tomography urography were performed, which revealed bilateral hydronephrosis and mass lesions around the renal pelvis. Partial resection of the masses and frozen section examination indicated the diagnosis of CD. However, the results of postoperative histopathology and immunohistochemistry combined with serum IgG4 were consistent with IgG4-RD. Both the patients recovered well after drug treatment without recurrence of the diseases.

Conclusions

Inflammatory pseudotumor of CD and IgG4-RD with kidney involvement are primarily diagnosed by postoperative histopathology and can pose a preoperative diagnostic challenge because these lesions can masquerade as kidney malignancy. Therefore, we recommend core biopsy as a nonnegligible procedure to evaluate renal masses and potentially prevent unnecessary surgical treatment.

Immunoglobulin G4-related disease: case report and literature review

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a rare and chronic progressive clinical entity, characterized by elevated serum IgG4 along with tissue infiltration by IgG4 + plasma cells. It is an immune-mediated fibro-inflammatory condition that can affect virtually any organ and tissue. IgG4-related lung disease (IgG4-RLD) occupies 14% of all IgG4-RD, with nonspecific symptoms and various abnormal radiographic patterns. Published data on IgG4-related hypertrophic pachymeningitis (IgG4-RHP), an increasingly recognized central nervous system manifestation of IgG4-RD, is also limited. Both lung and cranial dura involvement have not yet been reported until now. We further entail a review of the literature on the clinicopathologic features and differential diagnosis of this uncommon disease. We herein report an interesting case of a 70-year-old male patient admitted due to headache and fever. A magnetic resonance imaging (MRI) of the brain revealed extensive dural thickening with marked enhancement. Chest computed tomography (CT) scan showed nodular or mass-like consolidation and focal interstitial change. Thoracoscopic lung biopsy and lumbar puncture were conducted. After careful histopathological observation and consideration of alternative differential diagnoses, he was diagnosed with IgG4-related disease with lung and cranial dural involvement based upon significant elevation of serum and cerebrospinal fluid (CSF) IgG4 concentration. The patient was started on oral prednisolone 60 mg/day (1.0 mg/kg/day) for 14 days, and a tapering dose of 5 mg every 2 weeks followed by maintenance therapy at low dose for 3 months. His clinical manifestations, and serologic and imaging findings improved with steroid treatment. Currently, the patient remains well without disease progression. IgG4-RD should be considered as a differential when diagnosing other similar multisystemic lesions. Clinical examination, careful histological observation, and immunostaining for appropriate markers are essential in establishing the diagnosis. Clinicians should become familiar with this alternative differential diagnosis.

Renal Involvement in Retroperitoneal Fibrosis: Prevalence, Impact and Management Challenges

Retroperitoneal fibrosis (RPF) is a rare disorder consisting of idiopathic and various secondary forms and characterized by chronic inflammatory infiltrates and marked fibrosis in the retroperitoneal space. In idiopathic RPF (IRPF), 35–60% of cases have been reported to be IgG4-related RPF, the retroperitoneal lesions of IgG4-related disease (IgG4-RD). IRPF can frequently lead to renal insufficiency mediated by urinary tract obstruction and hydronephrosis irrespective of being IgG4-related or not. Clinical pictures, laboratory and imaging findings, and location of the urinary tract obstruction are generally similar in IgG4-related and non-IgG4-related IRPF although multiple organ involvement and serum IgG4 elevation may be characteristic of the IgG4-related forms. Periaortic/periarterial lesions are the most frequent cause of renal insufficiency. Although the response to glucocorticoids is generally good, relapse does occur in a considerable proportion of patients, and may require an additional immunosuppressive agent and/or urological intervention in cases with multiple relapses or refractory obstructive uropathy. In general, the prognosis of patients with IRPF is good, but careful attention needs to be paid to chronic kidney disease as a major complication and rupture of the affected aorta/artery as a life-threatening one. Further studies are necessary to better understand the pathogenesis of the disease and to establish the optimal diagnostic and therapeutic strategies for it.

Sonographic findings of immunoglobulin G4-related sialadenitis and differences from Sjögren's syndrome

OBJECTIVE

To evaluate ultrasonic features of the major salivary glands in patients with immunoglobulin G₄-related sialadenitis (IgG₄-RS) and to explore the differences between IgG₄-RS and Sjögren's syndrome (SS).

METHOD

We conducted the study in 150 patients with IgG₄-RS and 100 patients with SS. Ultrasonographic variables of the static images of major salivary glands were analysed. An experienced radiologist scored the confidence rating regarding the presence of the characteristic imaging findings using a five-grade rating system. Ultrasonography scores between IgG₄-RS and SS were compared.

RESULTS

The major salivary glands were significantly larger in patients with IgG₄-RS than in the SS group. The main features of ultrasonography of the salivary glands in IgG₄-RS were various hypoechoic lesions and increased colour Doppler signalling. In contrast, the major salivary glands in SS exhibited hyperechoic lines and/or spots and obscuration of the gland configuration. The scores of the summarized sonographic characteristics also showed statistically significant differences between the IgG₄-RS and SS groups.

CONCLUSION

This study revealed different ultrasonic features of the major salivary glands in patients with IgG₄-RS and SS. The scored sonographic features were helpful in differentiating IgG₄-RS from SS. Consequently, we suggest that ultrasonography of major salivary glands could be a useful imaging procedure in the evaluation of patients suspected of having IgG₄-RS.

Allergic Aspects of IgG4-Related Disease: Implications for Pathogenesis and Therapy

IgG4-related disease (IgG4-RD) is a rare systemic fibroinflammatory disease frequently associated with allergy. The pathogenesis of IgG4-RD is poorly understood, and effective therapies are limited. However, IgG4-RD appears to involve some of the same pathogenic mechanisms observed in allergic disease, such as T helper 2 (Th2) and regulatory T cell (Treg) activation, IgG4 and IgE hypersecretion, and blood/tissue eosinophilia. In addition, IgG4-RD tissue fibrosis appears to involve activation of basophils and mast cells and their release of alarmins and cytokines. In this article, we review allergy-like features of IgG4-RD and highlight targeted therapies for allergy that have potential in treating patients with IgG4-RD.

Application of regenerative medicine to salivary gland hypofunction

Dry mouth results from hypofunction of the salivary glands due to Sjögren's syndrome (SS), various medications, and radiation therapy for head and neck cancer. In severe cases of salivary gland hypofunction, sialagogues are not always effective due to the loss of salivary parenchyma. Therefore, regenerative medicine using stem cell therapy is a promising treatment for severe cases. Stem cells are classified into three groups: tissue stem cells, embryonic stem cells, and induced pluripotent stem cells. Tissue stem cells, such as hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs) and salivary stem/progenitor cells, could rescue irradiation-induced salivary gland hypofunction. Both HSCs and MSCs can rescue salivary gland hypofunction through soluble factors in a paracrine manner, while salivary stem/progenitor cells can reconstitute the damaged salivary glands. In fact, we clarified that CD133-positive cells in mouse submandibular glands showed stem cell features, which reconstituted the damaged salivary glands. Furthermore, we focused on the challenge of producing functional salivary glands that are three-dimensionally induced from mouse ES cells.

Marfan syndrome resulting from a rare pathogenic FBN1 variant, ascertained through a proband with IgG4-related arteriopathy

A 57-year-old man with a family history of aortic aneurysm was found, during assessment of unexplained fever, to have an infrarenal aortic aneurysm requiring immediate repair. Dilatation of popliteal and iliac arteries was also present. Progressive aortic root dilatation with aortic regurgitation was documented from 70 years leading to valve-sparing aortic root replacement at 77 years, at which time genetic studies identified a likely pathogenic FBN1 missense variant c.6916C > T (p.Arg2306Cys) in exon 56. The proband's lenses were normally positioned and the Marfan syndrome (MFS) systemic score was 0/20. Cascade genetic testing identified 15 other family members with the FBN1 variant, several of whom had unsuspected aortic root dilatation; none had ectopia lentis or MFS systemic score ≥ 7. Segregation analysis resulted in reclassification of the FBN1 variant as pathogenic. The combination of thoracic aortic aneurysm and dissection (TAAD) and a pathogenic FBN1 variant in multiple family members allowed a diagnosis of MFS using the revised Ghent criteria. At 82 years, the proband's presenting abdominal aortic aneurysm was diagnosed retrospectively to have resulted from IgG4-related inflammatory aortopathy.

Congruent microbiome signatures in fibrosis-prone autoimmune diseases: IgG4-related disease and systemic sclerosis

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) and systemic sclerosis (SSc) are rare autoimmune diseases characterized by the presence of CD4+ cytotoxic T cells in the blood as well as inflammation and fibrosis in various organs, but they have no established etiologies. Similar to other autoimmune diseases, the gut microbiome might encode disease-triggering or disease-sustaining factors.

METHODS

The gut microbiomes from IgG4-RD and SSc patients as well as healthy individuals with no recent antibiotic treatment were studied by metagenomic sequencing of stool DNA. De novo assembly-based taxonomic and functional characterization, followed by association and accessory gene set enrichment analysis, were applied to describe microbiome changes associated with both diseases.

RESULTS

Microbiomes of IgG4-RD and SSc patients distinctly separated from those of healthy controls: numerous opportunistic pathogenic Clostridium and typically oral Streptococcus species were significantly overabundant, while Alistipes, Bacteroides, and butyrate-producing species were depleted in the two diseases compared to healthy controls. Accessory gene content analysis in these species revealed an enrichment of Th17-activating Eggerthella lenta strains in IgG4-RD and SSc and a preferential colonization of a homocysteine-producing strain of Clostridium bolteae in SSc. Overabundance of the classical mevalonate pathway, hydroxyproline dehydratase, and fibronectin-binding protein in disease microbiomes reflects potential functional differences in host immune recognition and extracellular matrix utilization associated with fibrosis. Strikingly, the majority of species that were differentially abundant in IgG4-RD and SSc compared to controls showed the same directionality in both diseases. Compared with multiple sclerosis and rheumatoid arthritis, the gut microbiomes of IgG4-RD and SSc showed similar signatures; in contrast, the most differentially abundant taxa were not the facultative anaerobes consistently identified in inflammatory bowel diseases, suggesting the microbial signatures of IgG4-RD and SSc do not result from mucosal inflammation and decreased anaerobism.

CONCLUSIONS

These results provide an initial characterization of gut microbiome ecology in fibrosis-prone IgG4-RD and SSc and reveal microbial functions that offer insights into the pathophysiology of these rare diseases.

B cell targeted therapy for immunoglobulin G4-related disease

Glucocorticoids are the first-line drug for the remission induction therapy of immunoglobulin (Ig) G4-related disease. Achieving drug-free remission using glucocorticoids alone is difficult, however, and many patients require maintenance therapy with glucocorticoids and immunosuppressants. Studies have recently found that the number of peripheral memory B cells and plasmablasts is increased in IgG4-related disease and have indicated the efficacy of rituximab, which, in remission induction therapy, rapidly reduces serum IgG4 levels and has the tapering effect of glucocorticoids. Rituximab has been shown to reduce the risk of relapse more than oral immunosuppressants such as azathioprine. However, maintaining drug-free remission is difficult with a single course of rituximab alone, and many cases require maintenance therapy with rituximab. This article outlines the potential of B-cell targeted therapy, focusing on the efficacy, and safety of rituximab for IgG4-related disease.

IgG4-positive plasma cells are more often detected in chronic periapical lesions arising from permanent rather than primary teeth

AIM

To characterize plasma cell subsets in chronic periapical lesions affecting permanent and primary teeth.

METHODOLOGY

Only chronic periapical lesions without root canal treatment were selected. Twenty-one radicular cysts and 7 periapical granulomas affecting permanent teeth and 19 radicular cysts and 4 periapical granulomas affecting primary teeth were assessed for immunoglobulin (Ig) light chain (kappa and lambda), Ig heavy chain (IgG, IgG4, IgA, IgM and IgD) and plasma cell immunohistochemical markers (MUM1/IRF4, EMA and CD138). The data acquired were analysed by Student's t test, Mann-Whitney U, Friedman test followed by Dunn's multiple comparison test and Spearman's rank correlation.

RESULTS

All cases were polyclonal (having similar kappa/lambda light chain ratios). IgG was most abundant compared to other Ig heavy chains (all, P < 0.001); like Ig light chains, but unlike IgA, there was greater expression of IgG in the primary compared to the permanent dentition, for both radicular cysts (P < 0.001) and periapical granulomas (P = 0.53). Notably, IgG4 expression was greater in the permanent than the primary dentition, for both radicular cyst (P < 0.05) and periapical granuloma (P = 0.65). IgM and IgD expression was scarce and variable, whereas plasma cell populations were detected efficiently through EMA, CD138 and MUM1/IRF4 markers, the latter being more sensitive in both dentitions.

CONCLUSIONS

There were slight variations in the Ig light and heavy chain profiles in chronic periapical lesions when comparing the permanent and primary dentitions. The ability of IgG4+ plasma cell infiltration to modulate inflammatory responses in chronic periapical lesions arising from permanent as opposed to primary teeth should be considered in future studies.

Long-term effects of intensive B cell depletion therapy in severe cases of IgG4-related disease with renal involvement

IgG4-related disease (IgG4-RD) is an immune-mediated disorder often showing elevated serum IgG4 concentrations, dense T and B lymphocyte infiltration, and IgG4-positive plasma cells and storiform fibrosis. We prospectively evaluated for 4 years 5 patients with histologically proven IgG4-RD of whom 3 had tubulointerstitial nephritis (TIN) and 2 had retroperitoneal fibrosis (RPF). They received an intensive B depletion therapy with rituximab. The estimated glomerular filtration rate of TIN patients after 1 year increased from 9 to 24 ml/min per 1.73 m2. IgG/IgG4 dropped from 3236/665 to 706/51 mg/dl, C3/C4 went up from 49/6 to 99/27 mg/dl, and the IgG4-RD responder index fell from 10 to 1. CD20+ B cells decreased from 8.7 to 0.5%. A striking drop in interstitial plasma cell infiltrate as well as normalization of IgG4/IgG-positive plasma cells was observed at repeat biopsy. Both clinical and immunological improvement persisted over a 4-year follow-up. Treating these patients who were affected by aggressive IgG4-RD with renal involvement in an effort to induce a prolonged B cells depletion with IgG4 and cytokine production decrease resulted in a considerable rise in eGFR, with IgG4-RD RI normalization and a noteworthy improvement in clinical and histological features. Furthermore, the TIN subgroup was shown not to need for any maintenance therapy.

CGRP-Mediated Prolactin Upregulation: a Possible Pathomechanism in IgG4-Related Disease

Similar to other immune-mediated diseases, IgG4-related disease (IgG4-RD) is the disease that develops in genetically susceptible individuals exposed to external or endogenous antigens. In the present study, it was confirmed that MAG (myelin-associated glycoprotein) antibodies (IgG, IgG4, and IgM) were detected by immunofluorescence (IFA) in serum of the patients with IgG4-RD. In vivo, the levels of prolactin and Th2 cytokines in CGRP^+/- rats were higher than those in wild-type. Our findings indicate that the presence of CGRP-deficiency-mediated MAG antibodies is a probable molecular basis for the initial events which were triggered in IgG4-RD immune responses via prolactin upregulation.

Overlap Syndromes in Sarcoidosis: Clinical Features and Outcomes

Sarcoidosis is a multisystem inflammatory disease characterized by noncaseating granulomatous inflammation. While pulmonary sarcoidosis is most common, extrapulmonary involvement occurs in 50 to 74% of patients and can be the presenting abnormality in some patients. The diagnosis of sarcoidosis is based on a compatible clinical presentation in combination with granulomas on histology and exclusion of other causes. However, the absence of a diagnostic biomarker for sarcoidosis, in addition to the overlap of granulomatous inflammation and nonspecific clinical findings with other diseases, often results in a delayed diagnosis. Sarcoidosis overlap syndromes are typically described when sarcoidosis is diagnosed in the presence of another disease (concurrently or sequentially) with shared clinical and histologic features, or when sarcoidosis presents with clinical features typically observed in, but not diagnostic of, other diseases. Awareness of overlap syndromes is important for clinicians to avoid diagnostic errors and evaluate for concomitant diagnoses that may impact the management and outcome of sarcoidosis. This article is intended to provide an overview of these presentations and the most commonly associated diseases, with attention to their prevalence, clinical features, and reciprocal impacts on disease outcomes.

Multi-organ IgG4-related disease continues to mislead clinicians: A case report and literature review

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a multisystemic mass forming immune-mediated disease that affects almost every organ and is a diagnostic challenge for every clinician. There is a lack of adequate epidemiological data worldwide, and evidence-based treatment recommendations are not yet established. We report the first case of IgG4-RD from Lithuania and the Baltic Sea region presented with thyroiditis, orbital myositis, orbitopathy, uveitis, scleritis, sialadenitis, autoimmune pancreatitis and prostatitis.

CASE SUMMARY

A 54-year-old Caucasian male was admitted to our tertiary Centre complaining of severe weight loss, diarrhoea, abdominal pain, salivary gland swelling, sicca symptoms and diplopia. On examination, bilateral palpable masses in the projection of major salivary glands, severe protrusion of the left eyeball and cachexia were noted. The patient was previously diagnosed with autoimmune thyroiditis and endocrine ophthalmopathy. The magnetic resonance imaging (MRI) of the head revealed enlarged extraocular muscles indicating orbital myositis. The biopsy from the salivary gland mass indicated sialadenitis. Abdominal MRI showed signs of autoimmune pancreatitis, and a serological test revealed the elevated serum IgG4 concentration. The patient was then diagnosed with IgG4-RD and successfully treated with prednisolone. There was a significant clinical, serological and radiological improvement after one month of treatment and no signs of relapse within twenty months. However, it took almost 18 years and the efforts of eight different medical specialists to establish the correct diagnosis.

CONCLUSION

A comprehensive approach to the patient is essential to improving the recognition of rare immune system conditions, such as IgG4-RD.

Is Peyronie's an IgG4-related disease?

OBJECTIVE

We believe that IgG4 may have a role in the pathogenesis of Peyronie's disease (PD), and this role could be particularly beneficial for developing new strategies; therefore, we aimed to investigate the role of IgG4 in PD.

METHODS

This study included 3 groups with a total of 139 subjects: (I) PD group (n=61), (II) control group (n=48), and (III) benign prostatic hyperplasia (BPH) group (n=30). IgG4 measurement was performed using the enzyme-linked immunosorbent assay. Plaque size, penile curvature, and the presence of concomitant impotence were evaluated in the PD group. Impotence was assessed based on the International Index of Erectile Function (IIEF).

RESULTS

A significant difference was observed between the PD and control groups and between the PD and BPH groups with regard to IgG4 levels, while no significant difference was found between the BPH and control groups (p=0.0001, p=0.002, and p=0.07, respectively). The IgG4 levels were significantly higher in the PD than in the other groups. The cutoff value determined between the groups was 87.5, 82, and 31.5, respectively. Mean plaque size was 2.0±1.01 cm, and a significant relationship was found between plaque size and IgG4 concentration (p=0.02). Mean penile curvature was 35.6±25.1°, and a significant relationship was found between penile curvature of >60° and IgG4 concentration (p=0.001). Mean IIEF score was 19 (range, 7-25). Moreover, no significant relationship was found between erectile dysfunction and IgG4 concentration. Penile pain was present in 24 (39.3%) patients with PD.

CONCLUSION

The IgG4 levels were significantly increased in patients with PD, which implies that IgG4 may have a role in the pathogenesis of PD. This finding could be particularly beneficial for developing new strategies. Future studies with larger patient series are needed to substantiate our findings.

Occurrence of Immunoglobulin G4-related Disease during Chemotherapy for Advanced Breast Cancer

Immunoglobulin G4-related disease (IgG4-RD) is defined as an inflammatory lymphoproliferative disorder. The relationship between malignancies and IgG4-RD remains unclear. We herein present a case of IgG4-RD that occurred during chemotherapy for advanced breast cancer. In this case, it was challenging to determine which of these diseases was responsible for the patient's mediastinal lymphadenopathy. Lymphadenopathy with IgG4-RD was diagnosed by assessing the reactivity to corticosteroids, which were used as premedication in chemotherapy, over time. The administration of prednisolone, which was initiated to treat active IgG4-RD, led to stable systemic therapy for malignancy. It is imperative to assess the disease activity and consider each treatment.

Definite IgG4-related disease had no overlap with eosinophilic granulomatosis with polyangiitis in Korean patients: a pilot study in one centre

OBJECTIVES

Serum IgG4 may often increases in allergic diseases. Eosinophilic granulomatosis with polyangiitis (EGPA) has an allergic phase. For this reason, it was questionable whether IgG4-RD and EGPA may share some clinical and laboratory features. In this study, we investigated whether definite IgG4-RD might share those features with EGPA.

METHODS

We retrospectively reviewed the medical records of 42 Korean immunosuppressive drug-naïve patients with definite IgG4-RD. The American College of Rheumatology 1990 criteria for classification (the 1990 ACR criteria) for Churg-Strauss syndrome (CSS, known as EGPA) were applied to patients who were previously diagnosed with definite IgG4-RD and had no antineutrophil cytoplasmic antibody (ANCA). Definite IgG4-RD was defined when 3 components of the comprehensive diagnostic criteria were met.

RESULTS

The median age of 42 patients was 61.0 years and 69% of them were men. The median serum IgG4 level was 379.0 mg/dL and the median IgG4+/IgG+ cells ratio was 50.0%. The most common biopsy site was the salivary gland (14.3%). Antinuclear antibody was detected in 6 patients, and test results for ANCA were negative in all patients. Among 42 patients with definite IgG4-RD without ANCA, none of them met the 1990 ACR classification criteria for EGPA.

CONCLUSIONS

Definite IgG4-RD found to have no overlap with EGPA when the 1990 ACR criteria for CCS were applied to Korean patients. Key Points • None of 42 Korean patients with definite IgG4-RD without ANCA met the 1990 ACR classification criteria for EGPA. • Definite IgG4-RD found to have no overlap with EGPA in Korean patients without ANCA.

Clinicopathological differential diagnosis of IgG4-related disease: A historical overview and a proposal of the criteria for excluding mimickers of IgG4-related disease

IgG4-related disease (RD) is a relatively new entity, which was first proposed in 2001. Since then, clinical and pathological characteristics of the disease have been investigated. As IgG4-RD has been studied extensively, the diagnostic criteria for IgG4-RD of each organ and the comprehensive diagnostic criteria for IgG4-RD have also been developed. However, one of the biggest challenges in the field is distinguishing between IgG4-RD and mimickers, which show overlapping features with IgG4-RD. It is now known that some non-IgG4-RDs may meet the diagnostic criteria of IgG4-RD and can be misdiagnosed as IgG4-RD. However, accurate diagnosis is crucial, as the treatments for IgG4-RD and those for other diseases that may be misdiagnosed as IgG4-RD are different. This prompted us to create and propose comprehensive exclusion criteria for IgG4-RD. In this review, we have described the comprehensive exclusion criteria for IgG4-RD, with a historical overview of the disease. These exclusion criteria were recently created by the Research Program for Intractable Disease of the Ministry of Health, Labor, and Welfare of Japan, All Japan IgG4 team, to support correct and accurate diagnosis of IgG4-RD.

Sclerosing sialadenitis of the submandibular gland is rarely an immunoglobulin G4-related disease in the Finnish population

Chronic sclerosing sialadenitis may represent one of many manifestations of an immunoglobulin G4-related disease. However, existing studies typically consist of small patient cohorts rarely conducted in Western populations. The clinical behavior of chronic sclerosing sialadenitis, including follow-up data, warrants further study. Thus, we aimed to determine whether chronic sclerosing sialadenitis always presents as IgG4-related disease or associates with autoimmune diseases and to determine which additional examinations patients may require. Between 2000 and 2017, 51 patients undergoing submandibular gland resection within the Helsinki University Hospital area were diagnosed with chronic sclerosing sialadenitis. We re-evaluated all specimens and performed immunostaining for IgG4. IgG and CD31 stainings were performed for IgG4-positive specimens. IgG4-related disease diagnosis was defined by the Boston consensus statement criteria. We revised clinical data, distributing a follow-up questionnaire to patients to register symptoms of IgG4-related disease or autoimmune disease during follow-up. The chronic sclerosing sialadenitis criteria were fulfilled in 34 patients, whereby 17 were diagnosed as non-sclerosing chronic sialadenitis. In 19 cases, a sialolith associated with a salivary gland lesion. In total, 12 of 51 cases were recognized as IgG4-positive, while two met the criteria for IgG4-related disease. These two cases belonged to the non-sclerosing chronic sialadenitis group, and both involved other organs. The histopathological features between chronic sclerosing sialadenitis and non-sclerosing chronic sialadenitis overlapped regarding the degree of fibrosis and inflammatory infiltrates. In the Finnish population, chronic sclerosing sialadenitis of the submandibular gland does not appear to present as IgG4-related disease. Non-sclerosing chronic sialadenitis can associate with IgG4-related disease. A histopathological distinction between chronic sclerosing sialadenitis and non-sclerosing chronic sialadenitis is not always unequivocal and the presence of a sialolith does not exclude IgG4-positivity. Therefore, immunostaining for IgG4 should be performed when dense plasma cell infiltration is present in either non-sclerosing chronic sialadenitis or chronic sclerosing sialadenitis.

Current approach to diagnosis and management of retroperitoneal fibrosis

Retroperitoneal fibrosis is characterized by fibrotic lesions around the abdominal aorta and common ileac artery causing ureteral obstruction. Secondary retroperitoneal fibrosis is associated with malignant disease, drugs, exposure to radiation and surgery. In contrast, the majority of retroperitoneal fibrosis is classified into idiopathic retroperitoneal fibrosis, for which immunological etiology has been suggested. Recently, idiopathic retroperitoneal fibrosis has been considered to be a spectrum of immunoglobulin G4-related disease, a systemic inflammatory disease, the concept of which has been developed during the past decade. In the management of retroperitoneal fibrosis, assessment of systemic lesions associated with immunoglobulin G4-related disease and the exclusion of secondary retroperitoneal fibrosis is mandatory. Histological examination of retroperitoneal lesions is desired for accurate diagnosis and management. Laparoscopic or open biopsy is often beneficial, although it is more invasive than needle biopsy. Treatment for idiopathic retroperitoneal fibrosis consists of meticulous glucocorticoid therapy based on that for immunoglobulin G4-related disease, which is expected to be highly effective. Ureteral obstruction is usually managed with conservative procedures, such as ureteral stenting or percutaneous nephrostomy. The goal of treatment for retroperitoneal fibrosis should be freedom from the stent/nephrostomy with withdrawal of the glucocorticoid in addition to salvage of renal function; however, conservative management does not always provide favorable outcomes. In contrast, aggressive surgical treatment, such as ureterolysis, can achieve the goal; however, the procedure is associated with high morbidity. Establishment of a consensus about treatment for idiopathic retroperitoneal fibrosis, including the optimal indications for the invasive surgical procedure and conservative management, is desired.

Cytotoxic Tph-like cells are involved in persistent tissue damage in IgG4-related disease

OBJECTIVES

The aim of this study was to determine pathological features of T peripheral helper (Tph)-like (PD-1⁺CXCR5^-CD4⁺ T) cells in IgG4-related disease (IgG4-RD).

METHODS

Tph-like cells in the blood and submandibular glands (SMGs) from IgG4-RD patients were analyzed by flow cytometry. Correlations between level of a Tph-like cell subset and clinical parameters of IgG4-RD were investigated. The cytotoxic capacity of Tph-like cells was also examined. Expression profiles of a molecule related to a Tph-like cell subset in IgG4-RD SMGs were assessed by immunohistochemistry.

RESULTS

Tph-like cells from IgG4-RD patients highly expressed a fractalkine receptor, CX3CR1. Percentages of circulating CX3CR1⁺ Tph-like cells were significantly correlated with clinical parameters including IgG4-RD Responder Index, number of involved organs, and serum level of soluble IL-2 receptor. CX3CR1⁺ Tph-like cells abundantly possessed cytotoxic T lymphocyte-related molecules such as granzyme A, perforin, and G protein-coupled receptor 56. Functional assays revealed their cytotoxic potential against vascular endothelial cells and ductal epithelial cells. Immunohistochemistry showed that fractalkine was markedly expressed in vascular endothelial cells and ductal epithelial cells in IgG4-RD SMGs.

CONCLUSION

CX3CR1⁺ Tph-like cells are thought to contribute to persistent tissue injury in IgG4-RD and are a potential clinical marker and/or therapeutic target for inhibiting progression of IgG4-RD.

Orbital inflammation and colitis in pediatric IgG4-related disease: A case report and review of the literature

IgG4-related disease (IgG4-RD) is an inflammatory disorder characterized by tumor-like swelling in one or more organs, elevated serum IgG4 levels, and histological alterations with infiltration of IgG4-positive plasma cells. IgG4-RD is rare and likely underdiagnosed in children. We report a case of a 16-year-old girl with IgG4-positive colitis that developed weeks after IgG4-related ophthalmic disease and discuss diagnosis and treatment in the context of the literature available. Since the pathophysiology of IgG4-RD is unknown, treatment options are empiric and, for the most part, untargeted. Systemic corticosteroid treatment is the basis of anti-inflammatory treatment in IgG4-RD and induced early remission in our patient. During corticosteroid taper, the patient developed weight loss and intestinal inflammation. Histopathological assessment of the intestinal walls confirmed IgG4-positive colitis. Immune-modulating treatment with non-biologic (e.g., methotrexate (MTX) and mycophenolate mofetil) or biologic (rituximab) disease-modifying antirheumatic drugs has been reported in treatment refractory or corticosteroid-dependent patients. The patient responded to treatment with anti-inflammatory therapy with food rich in TGF-β2 (modulen) and MTX. This is one of the first pediatric patients reported with IgG4-related colitis extending the phenotype of pediatric IgG4-RD. International collaboration to prospectively document clinical presentation and treatment responses may help to further establish the phenotype and treatment options and to raise awareness for IgG4-RD.

Hypocomplementemia is related to elevated serum levels of IgG subclasses other than IgG4 in IgG4-related kidney disease

OBJECTIVES

This study investigated the clinical features of IgG4-RKD patients with hypocomplementemia compared with those without it, so as to clarify the factors related to hypocomplementemia.

METHODS

In this single-center retrospective study, we analyzed the clinical features of 25 patients with IgG4-RKD according to the presence/absence of hypocomplementemia. Additionally, we validated the results of a single-center study in a separate large multicenter cohort of 328 patients with IgG4-RD, and searched for factors related to hypocomplementemia.

RESULTS

Serum IgG levels (p < .001), non-IgG4 IgG levels, calculated as the total IgG minus IgG4 (p < .001), serum IgG1 levels (p = .017), and the number of involved organs (p = .018) were significantly higher in the hypocomplementemia group. At relapse of renal lesions in four patients, all had serum IgG4 re-elevation, with the three with hypocomplementemia presenting worsening of hypocomplementemia and re-elevation of non-IgG4 IgG levels. In a validation cohort of 328 patients with IgG4-RD, multivariate logistic regression analysis indicated elevation of non-IgG4 IgG levels to be an independent factor related to hypocomplementemia in the patients with IgG4-RKD.

CONCLUSION

The present study suggests that hypocomplementemia is associated with elevation of IgG subclasses other than IgG4 including IgG1 in IgG4-RKD.

A case report of IgG4-related disease: an insidious path to the diagnosis through kidney, heart and brain

Background

IgG4-related disease, described around the years 2000 as a form of autoimmune pancreatitis, is now increasingly accepted as a systemic syndrome. The diagnosis is based on both comprehensive and organ-specific criteria. For the kidney, Mayo clinic classification and the guidelines of the Japanese Nephrology Society are used. Ultimately, together with parameters that characterize every organ or apparatus involved, the key element is the confirmation of growing levels of IgG4 in blood or in tissues.

Case presentation

We describe a male patient with chronic renal failure associated to hypertension without proteinuria. IgG4-related disease was diagnosed through renal biopsy. After an initial positive response to steroids, he presented tinnitus, and histological assessment showed cerebral and subsequently cardiac damage, both IgG4-related. This case appears unique for the type of histologically documented cardiac and neurological parenchymal involvement, and at the same time, exemplifies the subtle and pernicious course of the disease. Frequently, blurred and non-specific signs prevail. Here, kidney damage was associated with minimal urinary findings, slowly progressive renal dysfunction and other factors that can be equivocated in the differential diagnosis. Neurological involvement was represented by tinnitus alone, while cardiac alterations were completely asymptomatic.

Conclusions

This report is representative of the neurological and cardiac changes described in the literature for IgG4-related disease, which may be correlated or not with the renal form and highlights the need, in some cases, of targeted therapeutic approaches. In addition to glucocorticoids, as in this case, rituximab may be necessary.