IgG4-Related Disease: Beyond Glucocorticoids

'Can we cure IgG4-related diseases?'

IgG4-related disease (IgG4-RD), recognized as a novel clinical entity, is a rare, chronic, immune-mediated systemic fibroinflammatory disorder of unknown origin with either synchronous or metachronous multi-organ involvement. Although the pathogenic mechanism remains unclear, possible multipathogenic factors such as genetic backgrounds, disease-specific or related antigens, and abnormal innate or adaptive immunity may be involved. Many immunocytes, including neutrophil extracellular trap, M2 macrophage, plasmablast, B cells, and T-cells (Th2-CD4+T, follicular helper T cells, and CD4+SLAMF7+cytotoxic T cells) play important roles in the pathogenesis. Conventional therapies with glucocorticoid or rituximab in combination with/without immunomodulators are recommended in all symptomatic patients with active IgG4-RD. Because of a few of randomized clinical trials, the comprehensive management for IgG4-RD has not been established yet. Targeted treatment approaches against the plasmablast to B cell lineage and the CD4+SLAMF7+cytotoxic T cell seem to be promising for the future-directed treatment.

Autoimmune Pancreatitis: A Review

Autoimmune pancreatitis is a rare condition of pancreatic inflammation with two classic subtypes. The emergence of a third subtype, ICI-induced pancreatitis, highlights the need for knowledge of each type to ensure accurate diagnosis and treatment. Abbreviations: AIP-Autoimmune pancreatitis; AIP-1-Type 1 autoimmune pancreatitis, also known as lymphoplasmacytic sclerosing pancreatitis (LPSP); AIP-2-Type 2 autoimmune pancreatitis, also referred to as idiopathic duct-centric pancreatitis (IDCP); AIP-3-Type 3 autoimmune pancreatitis, also known as immune checkpoint inhibitor (ICI)-induced autoimmune pancreatitis; IgG4-RD-Immunoglobulin G4-related disease.

The immunological pathogenesis of IgG4-related disease categorized by clinical characteristics

IgG4-related disease (IgG4-RD) is an immune disorder characterized by organ enlargement and fibrosis leading to functional impairment. Key immune cell subsets contributing to the pathogenesis of IgG4-RD include T follicular helper 2 cells (Tfh2), Tfh1, CX3CR1 + cytotoxic T cells (CX3CR1 + CTLs), Tregs and IgG4 + B cells. Tfh2 and Tregs are commonly involved in inducing IgG4 class-switching in this disease. Importantly, IgG4-RD can be classified into four clinical phenotypes based on the distribution of affected organs, with each phenotype showing different dominant immune cell subsets involved in its pathogenesis. Specifically, the clinical phenotype of retroperitoneal fibrosis/aortitis is characterized by CX3CR1 + CTLs as the dominant key immune cell subset, while Mikulicz disease with systemic involvement is dominated by Tfh2. In addition to classification based on organ distribution, IgG4-RD can also be categorized into phenotypes associated with malignancy or allergy. The malignancy phenotype is characterized by an increase in CXCR5 + CD2-double negative T cells compared to the allergy phenotype, along with a decrease in naive CD8 + T cells. Moreover, several autoantigens have been identified, and the presence of autoimmune phenotype has been revealed. Due to the pathogenicity of IgG1-type autoantibodies, Tfh1 may be important inducing IgG1 class-switching by IFNγ in autoimmune phenotype. In IgG4-RD with hypocomplementemia, activation of the complement pathway is thought to be induced by IgG1 or IgG2 antibodies, suggesting the involvement of Tfh1 in the disease pathogenesis. Therefore, elucidating the immunological features specific to each clinical characteristic is believed to lead to a deeper understanding of the pathogenesis of IgG4-RD and the discovery of novel therapeutic targets. This review provides an overview of the immunological mechanisms common to IgG4-RD as well as those specific to each clinical characteristic.

Treatment Strategies for Chronic Pancreatitis (CP)

Chronic pancreatitis (CP) and autoimmune pancreatitis (AIP) are diseases with overlapping features, both requiring complex management strategies. CP is characterized by pancreatic exocrine insufficiency (PEI) and pain, with treatment focused on symptom relief through pancreatic enzyme replacement therapy (PERT), pain control, and lifestyle and nutritional changes. However, the standard therapy does not address the underlying inflammation or fibrosis, which drives disease progression. AIP, on the other hand, presents with obstructive jaundice and fibrosis and is classified into two subtypes: Type 1 (AIP-1), linked to IgG4-related disease, and Type 2 (AIP-2), associated with inflammatory bowel disease. Treatment for AIP typically involves oral steroids. Immunomodulators and rituximab are used for recurrent or refractory cases. Novel therapies targeting the inflammation and fibrotic components of CP are being explored. A multidisciplinary approach is essential to optimize care and improve patients' outcomes.

Pharmacological Management of IgG4-Related Disease: From Traditional to Mechanism-Based Targeted Therapies

IgG4-related disease (IgG4-RD) is an immune-mediated disorder characterized by organ enlargement and dysfunction. The formation of tertiary lymphoid tissues (TLTs) in affected organs is crucial for understanding IgG4-RD, as T follicular helper (Tfh) 2 cells within TLTs drive IgG4+B cell differentiation, contributing to mass formation. Key cytokines IL-4 and IL-10, produced by Tfh2 cells, are essential for this process. Additionally, cytotoxic T cells and M2 macrophages significantly contribute to inflammation and fibrosis in the lesions. These insights into IgG4-RD have led to the development of innovative targeted therapies. While glucocorticoids are effective in many cases, they often cause disease flares during tapering and rarely result in long-term, treatment-free remissions. Long-term glucocorticoid use poses significant challenges owing to potential side effects, particularly in older patients who may already have complications such as diabetes and atherosclerotic diseases. In contrast, targeted therapies offer a promising alternative, potentially providing more effective disease control with fewer side effects. Current research is exploring several exciting approaches, including B-cell depletion, targeted immunomodulation of B cells, Bruton's tyrosine kinase inhibition, disruption of co-stimulation pathways, targeting the SLAMF7 cytokine or its receptor blockade (BAFF, IL-4, or IL-6), and JAK-STAT signaling pathway inhibition. These emerging strategies hold the promise of improving patient outcomes and advancing the management of IgG4-RD.

Human T follicular helper cells and their impact on IgE and IgG4 production across allergy, malignancy, and IgG4-related disease

Human T follicular helper (Tfh) cells play a crucial role in orchestrating B cell differentiation, maturation, and immunoglobulin class switching. Recent studies have underscored the presence of Bcl-6 + Tfh cells not only in secondary lymphoid organs but also within tertiary lymphoid structures at inflammatory sites, emphasizing their pivotal role in disease pathogenesis. Furthermore, Tfh cells have been found to transit between lesion sites, lymph nodes, and peripheral blood, as revealed by T cell receptor repertoire analysis. Among Tfh subsets, Tfh2 cells have emerged as central orchestrators in driving the production of IgE and IgG4 from B cells. Their critical role in diseases such as allergy, malignancy, and IgG4-related disease highlights their profound impact on balancing inflammation and immune tolerance. Our current review provides the molecular characteristics of human Tfh cells, the differentiation pathways of Tfh subsets, mechanisms by which Tfh subsets induce IgE and IgG4 production, and their clinical implications in allergy, malignancy, and IgG4-related disease.

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.

Comparative Analysis of Classification Criteria in IgG4-Related Disease and Evaluating Diagnostic Accuracy from a Retrospective Cohort in Clinical Practice

INTRODUCTION

We conducted a comprehensive comparative analysis of the Okazaki, Umehara, and American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) classification criteria for diagnosing immunoglobulin G4-related disease (IgG4-RD).

MATERIALS AND METHODS

A retrospective study was conducted in a single tertiary hospital, using expert clinical judgment as the gold standard. We compared the diagnostic accuracy of the Okazaki, Umehara, and ACR/EULAR criteria in a cohort of 41 patients with suspected IgG4-RD. We assessed sensitivity, specificity, and positive and negative predictive values for each criterion, and conducted a separate analysis based on four IgG4-RD subtypes.

RESULTS

A total of 30 patients were confirmed to have IgG4-RD and 11 were identified as mimickers. The Umehara criteria demonstrated the highest sensitivity (83.33%), followed by the ACR/EULAR 2019 (66.67%) and Okazaki (60.0%) criteria. All three criteria exhibited 100% specificity, with overall diagnostic accuracy ranging from 70% to 88%. The areas under the curve (AUC) were 0.917 (Umehara), 0.800 (Okazaki), and 0.833 (ACR/EULAR 2019), indicating significant diagnostic effectiveness (p < 0.000). Subtype analysis revealed that the Umehara and ACR/EULAR 2019 criteria were more effective in diagnosing pancreato-hepato-biliary involvement (subtype 1), while the Okazaki and ACR/EULAR 2019 criteria were more effective in diagnosing retroperitoneal fibrosis and/or aortitis (subtype 2).

CONCLUSIONS

Our study provides valuable insights into the diagnostic performance of the Okazaki, Umehara, and ACR/EULAR criteria for a cohort of patients with suspected IgG4-RD. The Umehara criterion demonstrated the highest sensitivity, suggesting its potential utility for screening purposes, while all three criteria showed consistent specificity.

Infective native arterial aneurysms and inflammatory abdominal aortic aneurysms: An overview with a focus on emergency settings

Infective native arterial aneurysms and inflammatory aortic aneurysms are rare but morbid pathologies seen by vascular surgeons in the emergency setting. Presentation is not always clear, and a full workup must be obtained before adopting a management strategy. Treatment is multidisciplinary and is tailored to every case based on workup findings. Imaging with computed tomography, magnetic resonance, or with fluorodeoxyglucose-positron emission tomography aids in diagnosis and in monitoring response to treatment. Open surgery is traditionally performed for definitive management. Endovascular surgery may offer an alternative treatment in select cases with acceptable outcomes. Neither technique has been proven to be superior to the other. Physicians should consider patient's anatomy, comorbidities, life expectancy, and goals of care before selecting an approach. Long-term pharmacological treatment, with antibiotics in case of infective aneurysms and immunosuppressants in case of inflammatory aneurysms, is usually required and should be managed in collaboration with infectious disease specialists and rheumatologists.

Successful remission induction of IgG4-related ophthalmic disease by obinutuzumab therapy: a retrospective study of 8 patients

OBJECTIVES

To evaluate the therapeutic efficacy and safety of obinutuzumab in remission induction for IgG4-related ophthalmic disease (IgG4-ROD) patients.

METHODS

Eight IgG4-ROD patients were retrospectively enrolled. They were intravenously administered 1000 mg obinutuzumab at baseline and examined for changes in physical signs, orbital structure imaging parameters, IgG4-related disease responder index (IgG4-RD RI), serological index, and adverse events during treatment. The number of treatment sessions was based on treatment response.

RESULTS

The mean IgG4-RD RI scores of all patients at baseline (7.75 ± 2.92) and after treatment (2.00 ± 0.76) were highly significantly different (P < 0.001). Six patients achieved complete remission (CR) (75%) and two patients achieved partial remission (25%). The mean serum IgG4 levels at baseline (9.45 ± 6.95 g/L) and after treatment (1.55 ± 1.09 g/L) showed a mean decrease of 83% (P = 0.0079). The serum IgG4 level correlated well with IgG4-RD RI at baseline and that after each treatment (r = 0.852, P < 0.01; r = 0.78, P < 0.001). In patients with CR, the serum IgG4 levels at baseline correlated positively with dose numbers required for CR (r = 0.86, P < 0.05). Five patients (62.5%) experienced infusion-related reactions (IRRs) during the first obinutuzumab infusion, while only one (12.5%) experienced IRRs during all subsequent eight infusions.

CONCLUSION

Obinutuzumab is a safe and promising therapeutic option for IgG4-ROD. It rapidly reduces ocular inflammation and serum IgG4 levels to avoid excessive corticosteroid usage and reduce potential risk of adverse events.

Autoimmune pancreatitis: Cornerstones and future perspectives

Autoimmune pancreatitis (AIP) is an autoimmune subtype of chronic pancreatitis resulting from the aberrant immune response against the pancreas, leading to inflammation and fibrosis. Although AIP is rare, its incidence is increasing and is often misdiagnosed as other pancreatic diseases. AIP is commonly classified into two types. Type 1 AIP (AIP-1) is typically associated with elevated serum immunoglobulin G4 (IgG4) levels and systemic manifestations, while type 2 AIP is typically a more localized form of the disease, and may coexist with other autoimmune disorders, especially inflammatory bowel diseases. Additionally, there is emerging recognition of a third type (type 3 AIP), which refers to immunotherapy-triggered AIP, although this classification is still gaining acceptance in medical literature. The clinical manifestations of AIP mainly include painless jaundice and weight loss. Elevated serum IgG4 levels are particularly characteristic of AIP-1. Diagnosis relies on a combination of clinical, laboratory, radiological, and histological findings, given the similarity of AIP symptoms to other pancreatic disorders. The mainstay of treatment for AIP is steroid therapy, which is effective in most cases. Severe cases might require additional imm-unosuppressive agents. This review aims to summarize the current knowledge of AIP, encompassing its epidemiology, etiology, clinical presentation, diagnosis, and treatment options. We also address the challenges and controversies in diagnosing and treating AIP, such as distinguishing it from pancreatic cancer and managing long-term treatment, highlighting the need for increased awareness and knowledge of this complex disease.

Recent progress on the treatment of type 1 autoimmune pancreatitis and IgG4-related disease

IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder recognized as a novel clinical entity with either synchronous or metachronous multiorgan involvement. Autoimmune pancreatitis (AIP) is classified into two types: type 1 AIP as a pancreatic manifestation of IgG4-RD and type 2 AIP with granulocytic epithelial lesion and occasional association with ulcerative colitis. Although the pathogenic mechanism still remains unclear, possible multipathogenic factors such as genetic factors, disease-specific or related antigens, and abnormal innate or adaptive immunity may be involved in the development of IgG4-RD. Many immunocytes including M2 macrophages, plasmablasts, B cells, and T-cells (Th2-CD4+T, follicular helper T-cells, and CD4+SLAMF7+cytotoxic T-cells) play important roles in the pathogenesis. Conventional induction and maintenance therapies with glucocorticoid or rituximab are recommended in all symptomatic patients with active IgG4-RD. In those at risk for irreversible damage in any organs, this should be done urgently, regardless of symptoms. As no randomized clinical trials other than glucocorticoid maintenance therapy for type 1 AIP have been performed, the comprehensive management for IgG4-RD has not been established yet. Targeted treatment approaches against the plasmablast to B cell lineage and the CD4+ SLAMF7+ cytotoxic T-cell seem to be promising for the future-directed treatment.

Comparison of the efficacy and safety of leflunomide versus mycophenolate mofetil in treating IgG4-related disease: a retrospective cohort study

OBJECTIVE

Combination therapy of glucocorticoids (GCs) plus leflunomide (LEF) and GCs plus mycophenolate mofetil (MMF) was reported to have good efficacy and safety in the management of IgG4-RD. However, studies comparing the efficacy and safety of these two combination therapies were unavailable. Herein, this study aimed to compare the efficacy and safety of GCs plus LEF and GCs plus MMF in treating IgG4-RD.

METHODS

This study included 130 newly diagnosed IgG4-RD patients who received the therapy of GCs plus LEF (group I) and GCs plus MMF (group II). Clinical data at baseline and after treatment, treatment response, relapse rate, and adverse effects were recorded and analyzed.

RESULTS

Patients in both groups responded well to the treatment in the 1st-month follow-up, and 100% of patients achieved treatment response. However, at the 6th and 12th-month follow-up, the total response rate of group II was higher than that in group I (75.6 vs. 53.7%, p = 0.038 and 85.4% vs. 61.0%, p = 0.013, respectively). In addition, the duration of disease remission in group II was longer than that in group I (9 (6-9) vs. 6 (6-6) months, p = 0.014). Moreover, more patients in group I had adverse effects compared with group II (36.6 vs. 7.3%, p < 0.01); and the most common adverse events of LEF were rash (12.2%) and elevation of liver enzymes (9.8%).

CONCLUSION

The combination therapy of GCs plus low-dose MMF had better efficacy and safety in the management of IgG4-RD compared with the therapy of GCs plus LEF.

Challenges for clinicians treating autoimmune pancreatitis: Current perspectives

Autoimmune pancreatitis (AIP) is a rare disease clinically characterized by obstructive jaundice, unintentional weight loss, acute pancreatitis, focal pancreatic mass, and diabetes. AIP is classified into two subtypes - type 1 and type 2 - according to pathological findings, clinical features, and serology test results, but some cases may be defined as type not otherwise in the absence of pathological findings and inflammatory bowel disease. To address the differences in diagnostic criteria by country, standard diagnostic criteria for AIP were proposed in 2011 by an international consensus of expert opinions. Differential diagnosis of AIP from pancreatic ductal adenocarcinoma is important but remains challenging for clinicians. Fortunately, all subtypes of AIP show dramatic response to steroid treatment. This review discusses the current perspectives on the diagnosis and management of AIP in clinical practice.

Multidisciplinary diagnosis and management of inflammatory aortic aneurysms

BACKGROUND

Inflammatory abdominal aortic aneurysms (IAAAs) are a variant involving a distinct immunoinflammatory process, with nearly one half believed to be associated with IgG4-related disease (IgG4-RD).

METHODS

MEDLINE and Google Scholar searches were conducted for English-language publications relevant to inflammatory aortic aneurysms from January 1970 onward. The search terms included inflammatory aortic aneurysms, aortitis, periaortitis, IgG4-related disease, and retroperitoneal fibrosis. Relevant studies were selected for review based on their relevance.

RESULTS

Morphologically, IAAAs are characterized by a thickened aneurysm wall often displaying contrast enhancement and elevated metabolic activity on fluorine-18 fluorodeoxyglucose-positron emission tomography imaging. A strong association exists with perianeurysmal and retroperitoneal fibrosis. Although the rupture risk appears lower with IAAAs than with noninflammatory abdominal aortic aneurysms (AAAs), the currently recommended diameter threshold for operative management is the same. Open repair has been associated with increased morbidity compared with noninflammatory AAAs, and a retroperitoneal approach or minimal dissection transperitoneal approach has been recommended to avoid duodenal and retroperitoneal structural injuries. Endovascular aneurysm repair has been increasingly used, especially for patients unfit for open surgery. It is important to exclude an infectious etiology before the initiation of immunosuppressive therapy or operative repair. Multimodality imaging follow-up is critical to monitor disease activity and secondary involvement of retroperitoneal structures by the associated fibrotic process. Maintenance of immunosuppressive therapy will be needed postoperatively for most patients with active systemic disease, especially those with IgG4-RD and those with persistent symptoms. Additional interventions aimed at ureteral decompression could also be required, and lifelong follow-up is mandatory.

CONCLUSIONS

Preoperative multimodality imaging is a diagnostic cornerstone for assessment of the disease extent and activity. IgG4-RD is an increasingly recognized category of IAAAs, with implications for tailoring adjunctive medical therapy. Open surgical repair remains the procedure of choice, although endovascular aneurysm repair is increasingly being offered. Maintenance immunosuppressive therapy can be offered according to the disease activity as assessed by follow-up imaging studies.

IgG4-Related Chronic Sinonasal Pseudotumor with Refractory Nasal Bleeding: A Case Report

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibro-inflammatory and idiopathic autoimmune disorder. IgG4-RD can be characterized by the presence of pseudotumors. Inflammatory pseudotumors may involve any part of a human organ. There are few reports of sinus lesions in IgG4-RD. An 82-year-old man has a history of chronic sinusitis for the last several years and no remarkable family history. Two years before disease presentation, the patient experienced intermittent nasal bleeding, stuffy nose, dizziness, and fatigue. Blood test revealed positive (160X) antinuclear antibody with a mixed speckled and nucleolar pattern, IgG level of 1370 mg/dL, and IgG4 level of 99.7 mg/dL. Computed tomography (CT) of the sinus revealed several calcifications in the sphenoid sinus. Surgical findings revealed tumor-like materials. Pathological examination of the soft tissues revealed acute and chronic granulomatous inflammation. Immunohistochemical analysis demonstrated high levels of positive-affinity markers of IgG, IgG4, and CD138 and a IgG4/IgG ratio > 40%. IgG4-RD with pseudotumor was diagnosed. The initial treatment was intravenous methylprednisolone 120 mg daily for three days and oral prednisolone 10 mg twice a day and azathioprine 50 mg daily. The efficacy of the treatment was insufficient, and nasal bleeding did not decrease. Subsequently administered intravenous rituximab 1000 mg monthly for 2 months. Following this treatment, nasal bleeding stopped. CT revealed reduction in nasal mucosal swelling compared with that in a previous scan. This report highlights that in cases with an inflammatory mass mimicking malignancy, IgG4RD should always be considered, and rituximab treatment is recommended upon failure of steroid and azathioprine therapy.

Left Ventricular Dysfunction Caused by IgG4-related Small Intramural Coronary Periarteritis

IgG4-related disease (IgG4-RD) is a systemic autoimmune disorder known to affect multiple organs. However, IgG4-RD rarely affects the myocardium. We herein report a case of left ventricular dysfunction due to cardiac involvement of IgG4-RD.

A rare case of IgG4-related disease masquerading as periurethral malignancy and review of the literature

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disease that typically manifests as mass lesions affecting almost any organ including the pancreas, lacrimal and salivary glands, liver, lung and kidney. However, IgG4-RD with urethra involvement is scarce. We describe a rare case of IgG4-RD involving the urethra mimicking urethral carcinoma and review the published literature. A 64-years-old female presented with progressive dysuria for more than 2 months. Pelvic gadolinium-enhanced magnetic resonance imaging revealed a huge mass encasing the urethra which showed obvious enhancement in the arterial phase. And contrast-enhanced ultrasound showed that the entire mass was heterogeneously enhanced and displayed a fast-forward and fast-out pattern, which was highly suggestive of malignant tumor. The diagnosis of IgG4-RD was finally established by ultrasound-guided transvaginal mass needle biopsy. The patient was treated with methylprednisolone and cyclophosphamide and dysuria disappeared in the first week of therapy. She has been followed up in our clinic for 1 year without recurrence. The diagnosis of IgG4-RD should be considered in the differential diagnosis of a periurethral mass. Ultrasound-guided transvaginal mass needle biopsy is a safe and well-established tissue sampling method and should be performed in order to avoid unnecessary surgery.

Recent Advances in Understanding the Role of TIGIT+ Follicular Helper T Cells in IgG4-Related Disease

IgG4-related disease (IgG4-RD) is a fibro-inflammatory disease characterized by elevated serum IgG4 levels and massive infiltration of IgG4+plasma cells. Although storiform fibrosis, obliterative phlebitis and IgG4+plasma cell infiltration are well described pathological features in this disease, the excessive formation of tertiary lymphoid organs (TLOs), particularly in the early phase of the disease lesions, has gained much attention. TLOs of IgG4-RD are orchestrated by specific immune cell subsets including follicular helper T cells (Tfh), CD20+ B cells, and CD21+ follicular dendritic cells (FDCs). Tfh is the key player of this disease because recent studies have suggested the pathological role of this immune cell subset in formation of TLOs, helping IgG4+plasma cell differentiation, inducing storiform fibrosis by secreting interleukin-4, and activating cytotoxic T cells by secreting interleukin-21. We have recently identified a new Tfh subset which expresses T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT). TIGIT+Tfh efficiently produces interleukin-21 through OX40 signal, and the increase in peripheral TIGIT+Tfh cells reflects disease activity in IgG4-RD. TIGIT is important to mediate the retention and positioning of TIGIT+Tfh within TLOs through interaction with CD155 expressed on CD21+ FDCs. In this review, we summarize and discuss recent progress in understanding the pathogenesis of IgG4-RD, focusing on TIGIT+Tfh.

IgG4-related disease in patients with idiopathic orbital inflammation

Background

To identify the prevalence of positive IgG4 immunostaining in orbital tissue among patients previously diagnosed with nongranulomatous idiopathic orbital inflammation (IOI) and to compare the clinical characteristics of patients with and without IgG4-positive cells.

Methods

A retrospective review of all patients with a histopathologic diagnosis of IOI was performed. Immunohistochemical staining was performed to identify IgG-positive cells and IgG4-positive cells. Multivariate analysis was performed using likelihood ratio-test logistic regression on the differences between IgG4-related disease (IgG4-RD) and non-IgG4-RD.

Results

Of the 45 patients included, 21 patients (46.7%) had IgG4-positive cells, with 52.4% being male and a mean age of 55.9 ± 13.4 years. Bilateral ocular adnexal involvement (adjusted odds ratio [aOR] = 9.45; P = 0.016) and infraorbital nerve enlargement (aOR = 12.11; P = 0.008) were frequently found in IgG4-RD patients. Complete remission occurred in 23.8% of IgG4-RD patients and 41.7% of non-IgG4-RD patients. IgG4-RD patients had more frequent recurrent disease than non-IgG4-RD patients.

Conclusions

Nearly 50% of IgG4-RD patients were previously diagnosed with biopsy-proven IOI. IgG4-RD was more frequent in patients with bilateral disease and infraorbital nerve enlargement, showing the importance of tissue biopsy in these patients. Immunohistochemistry studies of all histopathology slides showing nongranulomatous IOI are highly recommended to evaluate for IgG4-RD.

Salivary gland involvement in ANCA-associated vasculitis

OBJECTIVE

Salivary gland involvement in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis is rare, but can lead to the misdiagnosis of other diseases. The objective of this study was to clarify the characteristics of patients with salivary gland involvement.

METHODS

We conducted a systematic literature review of articles reporting salivary gland involvement in ANCA-associated vasculitis from the inception dates until May 2, 2021.

RESULTS

We identified 58 patients with salivary gland involvement. The mean age was 52 years, and men were predominantly affected (59%). Half of the patients presented with fever. Swelling of the salivary gland was the initial manifestation in 88% of the patients, unilaterally affected in 53%, and painful in 47%. The affected salivary glands were as follows: parotid gland alone (53%), submandibular gland alone (33%), and both parotid and submandibular glands (14%). Additionally, two patients had sublingual gland involvement. The most frequent clinical diagnosis was granulomatosis with polyangiitis (83%), followed by eosinophilic granulomatosis with polyangiitis (17%), while no patient was diagnosed with microscopic polyangiitis. PR3-ANCA positivity (72%) was predominant to MPO-ANCA positivity (6%), and ANCA was negative in 22% of the patients. Among 37 ANCA-positive patients, 6 patients (16%) were initially ANCA-negative, but subsequently became positive during the clinical course. The serum C-reactive protein levels were elevated in all the examined patients. On contrast-enhanced computed tomography, a finding suggestive of necrosis, which was heterogeneous enhancement with low-density areas, was found in 33% of the patients. Vasculitis, granulomatous inflammation, necrosis, or the presence of multinucleated giant cells was found in 83% of the biopsy samples of the affected salivary gland. Glucocorticoids with or without other immunosuppressive agents, such as cyclophosphamide were effective in most patients, but twelve patients (21%) experienced a relapse of the disease and nine patients (16%) died during the clinical course.

CONCLUSION

Salivary gland involvement can be an initial manifestation of ANCA-associated vasculitis. The recognition of this unusual atypical presentation is important for the early and accurate diagnosis and treatment.

Significance of high serum IgG4 in complete or non-full-fledged IgG4-related disease-a retrospective investigation of 845 patients and its clinical relevance

OBJECTIVE

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized heterogeneous, subacute, and usually silent autoimmune disease involving many organs with protean manifestations. However, high IgG4 in serum is not necessarily indicating an IgG4-RD. The aims of this study were to investigate the clinical relevance of high serum IgG4 level in IgG4-RD or non IgG4-RD patients, and to see if IgG4-RD in Taiwan differs from that in other parts of the world.

METHODS

Eight hundred forty-five patients with high IgG4 were retrospectively reviewed from January 2002 to May 2020 in Taipei Veteran General Hospital. Two hundred sixty-seven patients fulfilled IgG4-RD criteria and were categorized into pancreato-hepato-biliary disease, retroperitoneal fibrosis and/or aortitis, head/neck-limited disease, classic Mikulicz syndrome with systemic involvement, CNS-limited disease, sclerosing vasculitis, skin-limited disease, and sensorineural hearing disease. These manifestations were correlated to smoking, atopy, hyper-IgE/eosinophilia, aging, malignancies, and hypocomplementemia. Five hundred seventy-eight patients were not fulfilling the criteria but were also analyzed for the prevalence of allergy, malignancy, connective tissue diseases, lung diseases, and infections.

RESULTS

In IgG4-RD patients, 124 (46.4%) smoked. Top 4 clinical subtypes included Mikulicz syndrome with systemic involvement (33.3%), pancreato-hepatobiliary disease (31.4%), head/neck disease (19.4%), and retroperitoneal fibrosis/aortitis (12.7%). Top 4 co-morbid conditions included high serum IgE/eosinophilia (46.2%), hypocomplementemia (34%), malignancies (13.4%), and allergy (13.4%). Pancreato-biliary disease was associated with high IgE/eosinophilia (r² = 0.380, P = 0.025) and malignancy (r² = 0.211, P = 0.027), Miculicz syndrome with allergy (r² = 0.396, P < 0.01) and high IgE/eosinophil (r² = 0.396, P < 0.01), CNS diseases (r² = 0.973, P = 0.035) and sclerosing vasculitis (r² = 1, P < 0.01) with advanced age respectively, with the latter being also related to atopy and high IgE/eosinophilia (r² = 1, p < 0.01).

CONCLUSION

Smoking may precipitate IgG4-RD. IgG4-RD with pancreato-hepatobiliary disease is closely related to allergy and neoplasm, and those with Mikulicz syndrome may result from atopy. Elderly IgG4-RD patients tend to develop CNS pathology parallel to advancing of age. The disease may probably be originated from an unknown mechanism that may sporadically evolve into malignancies.

IgG4-related disease and idiopathic multicentric Castleman's disease: confusable immune-mediated disorders

IgG4-related disease (IgG4-RD) and idiopathic multicentric Castleman's disease (iMCD) are both rare systemic immune-mediated disorders. However, pathogenesis differs markedly between the two diseases, and differing therapeutic strategies are adopted: IgG4-RD is treated using a moderate dose of glucocorticoids or rituximab, while iMCD therapy involves an interleukin (IL)-6 targeted approach. Nonetheless, some clinical features of IgG4-RD and iMCD overlap, so differential diagnosis is sometimes difficult, even though the classification and diagnostic criteria of the diseases require careful exclusion of the other. The key findings in IgG4-RD are high IgG4/IgG ratio, allergic features, and germinal centre expansion involving T follicular helper cells, while iMCD involves polyclonal antibody production (high IgA and IgM levels), sheet-like mature plasma cell proliferation, and inflammatory features driven by IL-6. The distribution of organ involvement also provides important clues in both diseases. Particular attention should be given to differential diagnosis using combined clinical and/or pathological findings, because single features cannot distinguish IgG4-RD from iMCD. In the present review, we discuss the similarities and differences between IgG4-RD and iMCD, as well as how to distinguish the two diseases.

IgG4-related hypophysitis

Hypophysitis is a rare pituitary inflammatory disorder classified in different ways. Immunoglobulin G4-related disease (IgG4-RD), also a rare disease is a systemic fibro-inflammatory condition characterized by infiltration of tissue with IgG4-positive plasma cells; however prevalence of both of them probably is underestimated. In this paper, we present an Iranian patient with biopsy-proven IgG4-related hypophysitis and then review the clinical characteristics, laboratory, imaging, pathologic findings and therapeutic management as well as prognosis of 115 published cases of hypophysitis secondary to IgG4-related disease.

Refractory IgG4-related Pleural Disease with Chylothorax: A Case Report and Literature Review

We herein report a rare case of a 66-year-old man with refractory chylothorax. Although he had been treated with moderate doses of prednisolone (PSL) on suspicion of pleuritis with Sjögren syndrome, the pleural effusion expanded after the reduction of PSL. Further workup including histopathological examinations of pleura led to the diagnosis of IgG4-RD with bilateral chylothorax without any leakage from the thoracic duct. Combination therapy with high-dose PSL plus rituximab successfully decreased the pleural effusion. This is a very rare case of IgG4-related pleuritis with chylothorax and the first report of its successful treatment with rituximab.

UPLC-MS based plasma metabolomics and lipidomics reveal alterations associated with IgG4-related disease

OBJECTIVE

The pathogenesis of IgG4-related disease (IgG4-RD) remains unclear. Metabolomic profiling of IgG4-RD patients offers an opportunity to identify novel pathophysiological targets and biomarkers. This study aims to identify potential plasma biomarkers associated with IgG4-RD.

METHODS

Thirty newly diagnosed IgG4-RD patients, age-matched healthy controls and post-treated IgG4-RD patients were enrolled. Patients' clinical data, laboratory parameters and plasma were collected. Plasma was measured for ultraperformance liquid chromatography-tandem mass spectrometry based metabolomics and lipidomics profiling. Multivariate and univariate statistical analyses were conducted to identify potential biomarkers. The receiver operating characteristic and the correlations between biomarkers and clinical parameters were investigated.

RESULTS

The plasma metabolites are altered among healthy controls, newly diagnosed IgG4-RD and post-treated IgG4-RD groups. Of the identified features, eight metabolites were significantly perturbed in the IgG4-RD group, including glyceric acid 1,3-biphosphate (1,3-BPG), uridine triphosphate (UTP), uridine diphosphate glucose (UDP-Glc) or uridine diphosphate galactose (UDP-Gal), lysophospholipids, linoleic acid derivatives and ceramides. Receiver operating characteristic analysis indicated that UTP, UDP-Glc/UDP-Gal and LysoPC (18:1) had high sensitivity and specificity in diagnosis of IgG4-RD. A Pearson correlation analysis showed that 1,3-BPG and UTP were strongly correlated with clinical parameters.

CONCLUSION

IgG4-RD patients have a unique plasma metabolomic profile compared with healthy controls. Our study suggested that metabolomic profiling may provide important insights into pathophysiology and testable biomarkers for diagnosis of IgG4-RD.

Peripheral TIGIT+ T Follicular Helper Cells That Produce High Levels of Interleukin-21 via OX40 Represent Disease Activity in IgG4-Related Disease

Objectives

Multiple studies suggest that interleukin (IL)-21 plays a pivotal role in the differentiation of B cells and activation of cytotoxic T cells and is involved in the pathogenesis of IgG4-related disease (IgG4-RD). T cell immunoreceptor with immunoglobulin and ITIM domain (TIGIT) is a new marker of T follicular helper (Tfh) cells, yet its significance remains unknown. The objective of this study was to investigate whether TIGIT expression could detect high IL-21-producing peripheral Tfh populations and their association with disease activity in IgG4-RD.

Methods

TIGIT expression in peripheral CD4+T cell subsets was comprehensively analyzed by multi-color flow cytometry. Single cell mapping was performed by t-SNE method, and IL-21 production was compared in TIGIT+ and TIGIT-T cells. The effect of OX40 signal on cytokine expression was analyzed by RNA-sequencing. Clinical significance of TIGIT+ and TIGIT- peripheral T cells was analyzed in active patients with IgG4-RD, both at baseline and after 12 weeks of glucocorticoid treatment.

Results

Unbiased single cell mapping revealed two high IL-21-producing peripheral T cell populations; TIGIT+ Tfh and TIGIT-T helper cells. OX40 signal was associated with high IL-21 production in TIGIT+ Tfh and TIGIT-T helper cells. IL-21 production in Tfh cells correlated with the proportion of TIGIT+ cells in Tfh cells, serum IgG4 level, and scores of disease activity. Furthermore, the skewing toward peripheral TIGIT+ Tfh cells, particularly TIGIT+Tfh2 subset correlated with disease activity and was corrected by glucocorticoid treatment in IgG4-RD.

Conclusions

OX40 is associated with high IL-21 production in peripheral TIGIT+ Tfh cells, and the increase in peripheral TIGIT+ Tfh cells reflects disease activity in IgG4-RD.

Imaging of IgG4-Related Disease in the Head and Neck: A Systematic Review, Case Series, and Pathophysiology Update

This systematic review aims to clarify and comprehensively detail the sometimes variable published imaging features as well as the pathogenesis, clinical diagnostic criteria, and treatment options of IgG4-Related Diseases (IgG4-RD) in the head and neck to aid the radiologist in diagnosing relapse and new sites of disease. A literature search in PubMed and EMBASE for reported cases of IgG4-RD was performed in December 2019. Case reports or series of IgG4-RD in the head and neck in adults that included sufficient imaging and pathology findings were included. This yielded 50 reports. IgG4-RD locations included the orbits, thyroid, pituitary gland, paranasal sinuses, salivary and parotid glands, larynx, pharynx, cervical lymph nodes, meninges, and skull base. Most lesions demonstrated non-specific homogenous CT attenuation, diffuse enhancement, isointense/low T2 signal intensity, and low T1 signal intensity. 6 cases from our institution followed previously reported imaging patterns.

Characteristics and prognosis of ANCA-positive retroperitoneal fibrosis: A systematic literature review

OBJECTIVE

Anti-neutrophil cytoplasmic autoantibody (ANCA)-positive retroperitoneal fibrosis (RPF) is extremely rare. This study aimed to clarify the clinical characteristics and prognosis of patients with ANCA-positive RPF.

METHODS

We conducted a systematic literature review of articles reporting on ANCA-positive RPF from the database inception dates until March 8, 2020.

RESULTS

We identified 19 patients with ANCA-positive RPF with a mean age of 62 years; a male dominance (68.4%) was noted. Most patients presented with systemic symptoms and/or lower back or abdominal pain. Proteinase 3 (PR3) -ANCA positivity was predominant compared with myeloperoxidase (MPO)-ANCA (63.2% vs. 36.8%, respectively), and all patients showed elevated serum C-reactive protein levels. Of note, 26.7% of patients had isolated RPF without any other ANCA-associated systemic organ involvement. Regarding typical manifestations of ANCA- associated vasculitis, ear, nose, and throat involvement occurred in 26.3%, lung involvement in 36.8%, and kidney involvement (rapidly progressive glomerulonephritis) in 31.6% of patients. Necrosis and granulomatous inflammation, vasculitis, and multinucleated giant cells were pathologically observed in tissue sections of RPF, whereas tertiary lymphoid organ formation was not identified. Glucocorticoids with or without other immunosuppressive treatments were effective in most patients, but 4 patients experienced disease relapse during the clinical course. All relapsed patients were positive for PR3-ANCA.

CONCLUSION

Clinical features of ANCA-positive RPF are associated with systemic inflammatory components such as fever and elevated serum C-reactive protein levels. ANCA-. positive RPF presents as an "isolated" involved organ in one-third of patients. Immunosuppressive treatments are effective, but the disease can recur, particularly in PR3-ANCA-positive patients.

Steroid Therapy and Steroid Response in Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP), a unique subtype of pancreatitis, is often accompanied by systemic inflammatory disorders. AIP is classified into two distinct subtypes on the basis of the histological subtype: immunoglobulin G4 (IgG4)-related lymphoplasmacytic sclerosing pancreatitis (type 1) and idiopathic duct-centric pancreatitis (type 2). Type 1 AIP is often accompanied by systemic lesions, biliary strictures, hepatic inflammatory pseudotumors, interstitial pneumonia and nephritis, dacryoadenitis, and sialadenitis. Type 2 AIP is associated with inflammatory bowel diseases in approximately 30% of cases. Standard therapy for AIP is oral corticosteroid administration. Steroid treatment is generally indicated for symptomatic cases and is exceptionally applied for cases with diagnostic difficulty (diagnostic steroid trial) after a negative workup for malignancy. More than 90% of patients respond to steroid treatment within 1 month, and most within 2 weeks. The steroid response can be confirmed on clinical images (computed tomography, ultrasonography, endoscopic ultrasonography, magnetic resonance imaging, and 18F-fluorodeoxyglucose-positron emission tomography). Hence, the steroid response is included as an optional diagnostic item of AIP. Steroid treatment results in normalization of serological markers, including IgG4. Short- and long-term corticosteroid treatment may induce adverse events, including chronic glycometabolism, obesity, an immunocompromised status against infection, cataracts, glaucoma, osteoporosis, and myopathy. AIP is common in old age and is often associated with diabetes mellitus (33-78%). Thus, there is an argument for corticosteroid therapy in diabetes patients with no symptoms. With low-dose steroid treatment or treatment withdrawal, there is a high incidence of AIP recurrence (24-52%). Therefore, there is a need for long-term steroid maintenance therapy and/or steroid-sparing agents (immunomodulators and rituximab). Corticosteroids play a critical role in the diagnosis and treatment of AIP.

IgG4-related disease in a multi-ethnic community: clinical characteristics and association with malignancy

BACKGROUND

Immunoglobulin-G4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory condition that can affect multiple organs. Despite growing interest in this condition, the natural history and management of IgG4-RD remain poorly understood.

AIM

To describe the clinical characteristics, treatment and outcomes of IgG4-RD in a multi-ethnic UK cohort, and investigate its possible association with malignancy.

DESIGN

Retrospective analysis of case-note and electronic data.

METHODS

Cases were identified from sub-specialty cohorts and a systematic search of an NHS trust histopathology database using 'IgG4' or 'inflammatory pseudotumour' as search terms. Electronic records, imaging and histopathology reports were reviewed.

RESULTS

In total, 66 identified cases of IgG4-RD showed a similar multi-ethnic spread to the local population of North West London. The median age was 59 years and 71% of patients were male. Presenting symptoms relating to mass effect of a lesion were present in 48% of cases and the mean number of organs involved was 2.4. Total of 10 patients had reported malignancies with 6 of these being haematological. 83% of those treated with steroids had good initial response; however, 50% had relapsing-remitting disease. Rituximab was administered in 11 cases and all achieved an initial serological response. Despite this, seven patients subsequently relapsed after a mean duration of 11 months and four progressed despite treatment.

CONCLUSIONS

We report a large UK-based cohort of IgG4-RD that shows no clear ethnic predisposition and a wide range of affected organs. We discuss the use of serum IgG4 concentrations as a disease marker in IgG4-RD, the association with malignant disease and outcomes according to differing treatment regimens.

The treatment outcomes in IgG4-related orbital disease: a systematic review of the literature

IgG4-related disease (IgG4-RD) is an immune-mediated systemic fibro inflammatory disease. Treatment of IgG4-related orbital disease (IgG4-ROD) is often indicated to relieve the symptoms and to prevent complications. For IgG4-ROD, no international formal treatment guidelines are available and the optimal treatment strategy is uncertain. In this systematic review, we describe the efficacy of conventional and biologic disease-modifying antirheumatic drugs (DMARDs) in IgG4-ROD. A systematic search of Embase, Medline, Web-of-Science, PubMed publisher, Cochrane and Google Scholar was performed for treatment outcomes in IgG4-ROD. Relevant articles on treatment of IgG4-ROD were retrieved to last date of inclusion 3 January 2018. The following inclusion criteria were used: articles in English or English translation, studies evaluating the use of DMARDs (conventional and biologic) in the treatment of IgG4-ROD. Meta-analysis and review articles were excluded. A final selection after full-text evaluation was made by independent reviewers, based on treatment of IgG4-ROD with DMARDs and the availability of treatment outcomes. With this systematic review, we identified 35 studies and case reports/series on IgG4-ROD, describing 95 patients, treated with conventional and/or biologic DMARDs. The success of conventional DMARDs varies between 36% and 75% in patients with IgG4-ROD, while rituximab is successful in the majority (93%) of the patients. Based on this systematic review, rituximab is the most effective DMARD in IgG4-ROD, while the efficacy of conventional DMARDs is limited. We propose early initiation of rituximab in case of refractory and organ- or life-threatening disease.

Characteristics and prognosis of IgG4-related periaortitis/periarteritis: A systematic literature review

OBJECTIVE

Immunoglobulin G4 (IgG4)-related disease is a systemic chronic fibroinflammatory disease that can affect almost every organ of the body. IgG4-related periaortitis/periarteritis is a newly recognized subset of IgG4-related disease, and its characteristics and prognosis remain unclear. We investigated the clinical characteristics and prognosis of IgG4-related periaortitis/periarteritis.

METHODS

We performed a systematic literature review of IgG4-related periaortitis/periarteritis. Additionally, we have summarized the characteristics and prognosis of IgG4-related coronary arteritis.

RESULTS

We investigated 248 patients with IgG4-related periaortitis/periarteritis. All studies reported the condition in elderly patients, and male predominance was observed. The infra-renal abdominal aorta and iliac arteries were the most commonly affected sites. Most reports showed the serum C-reactive protein elevation in this disease entity, in contrast to non-vascular IgG4-related disease. Based on radiological findings observed in 27 patients with IgG4-related coronary arteritis, vasculitic lesions were classified into 3 types: stenotic (67% of patients), aneurysmal (42%), and diffuse wall thickening type (92%). Serum IgG4 level, but not C-reactive protein level, was associated with the number of affected organs in IgG4-related coronary arteritis. Corticosteroid treatment with or without cardiac surgery or percutaneous coronary intervention was effective in most patients with IgG4-related coronary arteritis; however, 33% of patients showed an unfavorable clinical course including disease progression, relapse, or death. Pre-treatment stenosis and/or aneurysms were associated with progression of stenosis or aneurysm after corticosteroid treatment.

CONCLUSION

Most clinical characteristics were similar between the IgG4-related periaortitis/periarteritis and the non-vascular IgG4-related disease groups; however, serum C-reactive protein level elevation was observed only in the former. Although corticosteroid treatment was effective, this disease can be life-threatening secondary to myocardial infarction, aortic dissection, and aneurysmal rupture. Pre-treatment evaluation of stenosis or aneurysms is important for predicting progression of stenosis or aneurysm after corticosteroid treatment.

Efficacy and safety of iguratimod plus corticosteroid as bridge therapy in treating mild IgG4-related diseases: A prospective clinical trial

Aim

The purpose of this study is to evaluate the therapeutic efficacy and safety of iguratimod plus corticosteroid as bridge therapy in the treatment of mild immunoglobulin G4‐related disease (IgG4‐RD).

Methods

Newly diagnosed IgG4‐RD patients, without internal organ involvement were enrolled. Patients were given one dose of diprospan, intramuscular injection, and iguratimod, 25 mg, twice daily, for 24 weeks and were followed up at 0, 12 and 24 weeks. Follow‐up indexes included IgG4‐RD responder index (IgG4‐RD RI), serology and imaging, plasma cytokines and adverse drug effect. Flow cytometry was performed for T, B cell subsets and plasma was collected for liquid chromatography mass spectrometry (LC‐MS)‐based metabolomic profiling and data processing.

Results

Thirty patients were enrolled. At week 24, 9 (30.0%) patients achieved complete response, 17 (56.7%) patients with partial response, and 4 (13.3%) patients had no response to treatment. IgG4‐RD RI, serum IgG and IgG4 levels decreased significantly at weeks 12 and 24 after treatment, as well as CD3+ CD8+ T cells, plasmablast/plasma cells and memory B cells. The LC‐MS based plasma metabolomic profiles revealed significant changes between untreated patients and healthy donors, which became much similar to normal states after treatment.

Conclusion

Iguratimod plus corticosteroid as bridge therapy is effective for the treatment of mild IgG4‐RD, it can improve the clinical symptoms, reduce serum IgG and IgG4 levels, especially plasmablasts/plasma cells and memory B cells. In addition, the metabolite profiling became similar to normal controls after treatment.

IgG4-related dacryocystitis and aortitis: A new association

A 73-year-old woman with a history of muscular weakness and dyspnoea of unknown etiology was referred to our Ophthalmology Department for dacryocystitis. Lacrimal sac biopsy revealed IgG4 plasma cell infiltration and systemic diagnosis was done based on this, allowing an appropriate treatment to be established. To our knowledge, this is the first reported case of IgG4-related dacryocystitis associated to aortitis.

Eosinophilia and Kidney Disease: More than Just an Incidental Finding?

Peripheral blood eosinophilia (PBE), defined as 500 eosinophils or above per microliter (µL) blood, is a condition that is not uncommon but often neglected in the management of patients with chronic kidney disease (CKD), acute kidney injury (AKI), or patients on renal replacement therapy (RRT). The nature of PBE in the context of kidney diseases is predominantly secondary or reactive and has to be distinguished from primary eosinophilic disorders. Nonetheless, the finding of persistent PBE can be a useful clue for the differential diagnosis of underdiagnosed entities and overlapping syndromes, such as eosinophilic granulomatosis with polyangiitis (EGPA), IgG4-related disease (IgG4-RD), acute interstitial nephritis (AIN), or the hypereosinophilic syndrome (HES). For patients on RRT, PBE may be an indicator for bio-incompatibility of the dialysis material, acute allograft rejection, or Strongyloides hyperinfection. In a subset of patients with EGPA, eosinophils might even be the driving force in disease pathogenesis. This improved understanding is already being used to facilitate novel therapeutic options. Mepolizumab has been licensed for the management of EGPA and is applied with the aim to abrogate the underlying immunologic process by blocking interleukin-5. The current article provides an overview of different renal pathologies that are associated with PBE. Further scientific effort is required to understand the exact role and function of eosinophils in these disorders which may pave the way to improved interdisciplinary management of such patients.

IgG4-related inflammatory pseudotumor of the brain parenchyma: a case report and literature review

A 29-year-old male with a 4-month history of binocular temporal visual field defect, 1-month history of memory loss and 5-day history of headache was admitted to our hospital. Brain MRI showed progressive signal abnormalities in the brain parenchyma. His laboratory tests showed elevated serum IgG4 and liver dysfunction. Abdominal CT, ultrasound and liver biopsy showed chronic liver disease. According to the diagnostic criteria of IgG4-related disease, IgG4-related inflammatory pseudotumor of brain parenchyma was considered. After methylprednisolone treatment, his symptoms improved and brain lesion reduced. This is the second reported case of a tumefactive lesion of the brain with serum IgG4 elevation, which was responsive to steroid treatment. Coincidentally, his mother had similar medical history and imaging findings, and was subspecialty diagnosed with the same disease, but without pathological and immunohistochemical confirmation. This suggests that the disease may be hereditary. It is important to recognize IgG4-related inflammatory pseudotumors of the brain parenchyma so that patients do not undergo unnecessary surgical or other procedures.