Type 1 autoimmune pancreatitis is a common manifestation of IgG4-related disease (IgG4-RD). However, there is a paucity of literature characterizing pancreatic damage and symptom burden in IgG4-RD.

We performed a cross-sectional analysis of patients who fulfilled the ACR/EULAR IgG4-RD Classification Criteria. Disease features and complications were collected by medical record review. A survey regarding symptoms and disease history was distributed to all patients. Characteristics were compared between patients with and without autoimmune pancreatitis.

Of 303 patients who fulfilled Classification Criteria at the time of the chart review, 118 (39 %) had evidence of autoimmune pancreatitis. Overt indicators of acute pancreatitis (e.g., abdominal pain, nausea/emesis, elevated serum lipase) each occurred in fewer than 50 % of patients with autoimmune pancreatitis. Diabetes mellitus (DM), exocrine pancreatic insufficiency (EPI), or both were present in 47 %, 48 %, and 21 % of the autoimmune pancreatitis patients, respectively. After encouraging all patients to have fecal elastase measured, 40/49 (82 %) stool samples had low elastase concentrations. 9/118 (8 %) had undergone pancreatic resections before the diagnosis was established. 162/325 (50 %) completed surveys (n = 81 [50 %] with autoimmune pancreatitis). Patients with autoimmune pancreatitis reported a higher burden of abdominal pain, weight loss, and changes in stool than those without (all p < 0.05).

Despite an often subclinical presentation, autoimmune pancreatitis is associated with EPI, DM, or both in a high percentage of patients with IgG4-RD. While symptomatic acute pancreatitis may not be common, patient-reported symptom burden due to IgG4-related autoimmune pancreatitis or its complications is greater than previously appreciated.

To evaluate the prevalence and clinical associations of anti-C1q antibodies in IgG4-related disease (IgG4-RD), focusing on renal involvement and cutaneous small-vessel vasculitis (CSVV).

We enrolled patients who met the revised 2020 Comprehensive Diagnostic Criteria and/or the 2019 ACR/EULAR Classification Criteria for IgG4-RD. Variables included demographics, organ involvement, clinical phenotypes, disease activity, serum biomarkers, follow-up duration, remission and relapses. Anti-C1q antibodies were measured using a quantitative enzyme-linked immunosorbent assay (cut-off <10 U/ml).

Seventy patients with a mean age of 52.1 years were included. Thirty-four patients (48.6%) were male. Anti-C1q antibodies were positive in 74.3%, with a median level of 19.8 U/ml. Patients with active disease had higher anti-C1q antibody levels than inactive patients (P = 0.03). Renal involvement was more frequent in anti-C1q positive patients (P = 0.01). Six patients (8.6%) had CSVV, and all had positive anti-C1q levels. All exhibited palpable purpura and one patient had urticarial-like lesions. These patients had multi-organ involvement, and most had high IgG, IgG1, IgG4 and hypocomplementemia. Skin biopsies in three patients showed leukocytoclastic vasculitis with lymphocytic and eosinophilic infiltrates. Anti-C1q antibody levels correlated negatively with levels of C3 and C4, and positively with levels of IgG1, IgG4, and serum free light chains. Anti-C1q positivity did not predict relapse-free survival.

This study is the first to evaluate anti-C1q antibodies in IgG4-RD, finding a high prevalence, particularly in patients with renal involvement and CSVV. The results support the hypothesis that immune complex-mediated complement activation contributes to IgG4-RD pathogenesis.

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory condition marked by tumefactive lesions, IgG4+ plasma cell-rich infiltrates, storiform fibrosis, and obliterative phlebitis. Its multisystem involvement and overlap with malignancies, infections, and immune disorders complicate diagnosis despite recent classification advances. This study summarizes diagnostic challenges, highlights the role of histopathology as per the 2019 classification criteria established by the American College of Rheumatology and the European League Against Rheumatism (ACR/EULAR), and explores emerging tools to improve diagnostic accuracy. ACR/EULAR classification emphasizes three cardinal histopathological features (storiform fibrosis, obliterative phlebitis, or dense lymphoplasmacytic infiltrates) combined with an IgG4+/IgG+ plasma cell ratio >40% and organ-specific IgG4+ thresholds. While serum IgG4 levels are often elevated, their poor specificity necessitates confirmatory biopsy. Diagnostic limitations include sampling variability due to patchy fibrosis, interobserver discrepancies in immunohistochemical interpretation, and differentiation from mimics like lymphoma. Emerging solutions incorporate novel biomarkers (plasmablasts, anti-annexin A11) and advanced techniques (flow cytometry, digital pathology). Future research directions should focus on AI-assisted pattern recognition, multi-omics profiling, and organ-specific criteria refinement. While histopathology remains the diagnostic cornerstone, a multidisciplinary approach integrating clinical, radiological, and laboratory data is vital. Innovations in biomarkers promise improved diagnostic accuracy and personalized care, balancing novel advancements with foundational pathological evaluation.

To analyze the clinical characteristics of malignant lymphoma that closely resembles IgG4-related disease (IgG4-RD).

This study retrospectively analysis involving 31 patients who were lymphoma mimicking, IgG4-RD and 50 contemporaneous IgG4-RD patients serving as controls. Lymphoma mimicking IgG4-RD was defined as presenting with masses in the typical sites of IgG4-RD, with or without elevated serum IgG4 levels, and ultimately confirmed to be lymphoma. The clinical data, including the extent of lymph node involvement, maximum diameter of lymph nodes, systemic symptoms, and laboratory parameters were assessed. Student's t-test, the Mann-Whitney test, and the chi-squared test were used to compare the two groups.

Fever emerged as a distinctive feature in lymphoma patients. Compared to IgG4-RD, lymphoma patients exhibited a greater extent of lymph node involvement (p < 0.001), larger maximum diameters of lymph nodes (p = 0.007), and higher frequency of enlargement in supraclavicular (41.9% vs 10.0%; p = 0.001), armpit (45.2% vs 16.0%; p = 0.004), retroperitoneal (70.9% vs 10.0%; p < 0.001), and groin lymph nodes (41.9% vs 8.0%; p < 0.001). In contrast, IgG4-RD patients were more likely to show involvement of submandibular gland (58.0% vs 29.0%; p = 0.015) and pancreatic (44.0% vs 9.7%; p = 0.001). Additionally, lymphoma patients presented with higher levels of erythrocyte sedimentation rate (ESR) (p = 0.010), C-reactive protein (CRP) (p < 0.001), and lactate dehydrogenase (LDH) (p = 0.002), along with a higher prevalence of anemia (35.5% vs 4.0%; p < 0.001) and lower albumin levels (p = 0.039), while IgG4-RD patients had higher IgG4/IgG ratio (p < 0.001) and lower complement 3 (C3) (p = 0.009) levels than lymphoma patients.

Although patients with malignant lymphoma and IgG4-RD share some overlapping presentations, they differ significantly in some distinct features, including fever, pattern of lymph node and organ involvement distribution, and some laboratory parameters. Key Points • IgG4-related disease (IgG4-RD) is an immune-mediated disorder characterized by elevated serum IgG4 levels, presenting lymphadenopathy and tumor-like sclerosing lesions in extranodal sites. • Lymphoma, a malignancy that originates from lymphocytes, can present with a variety of clinical manifestations, including painless swelling of lymph nodes and enlargement of different organs. • While patients with malignant lymphoma and IgG4-RD share certain overlapping clinical presentations, they exhibit significant differences in distinct features, including fever, patterns of lymph node and organ involvement, and various laboratory parameters.

IgG4-related disease (IgG4-RD) is a fibro-inflammatory disorder usually characterized by multi-organ involvement. Its pathogenesis is complex and involves genetic and environmental factors, while immune responses usually mediate organ damage and promote fibrosis, which is a key feature of the disease. IgG4 responses, however, are not exclusive to IgG4-RD and can be encountered in other diseases with phenotypes that partially overlap that of IgG4-RD. Although IgG4-RD has clinical and histological hallmarks, the lack of validated diagnostic criteria often makes the diagnosis challenging, requiring a multi-dimensional approach that integrates clinical, radiological and serological data. The present Review covers recent advances in the understanding of disease drivers and its clinical phenotypes, mainly focusing on the differential diagnosis with potential IgG4-RD mimickers, namely histiocytoses, lymphoproliferative disorders, systemic vasculitides and other immune-mediated conditions. The Review also provides a schematic approach to IgG4-RD treatment, including a brief overview of glucocorticoid-sparing agents and emerging therapies, from B cell-depleting monoclonal antibodies to cytokine-targeting drugs, the majority of which are currently under investigation in randomized clinical trials.

PurposeTo present the first case of isolated corneal involvement in IgG4-RD, managed successfully with oral mucosal grafting due to the destructive course of the disease.Case reportA 56-year-old female one-eyed patient was referred to our clinic with a diagnosis of unresponsive infectious corneal melting. The ophthalmologic examination revealed light perception visual acuity, intense conjunctival inflammation and an infected area of approximately 4 × 5 mm with accompanying melting. Her medical history includes a diagnosis of dry eye disease that has persisted for over a decade, multiple previous corneal transplant surgeries in the right eye with similar complaints, and subsequent evisceration surgery. Her complaints in the left eye had increased over the previous six months, and she had undergone eight instances of amniotic membrane transplantation at an external medical facility. Corneal scraping, conjunctival and corneal biopsy were performed. The histopathologic examination and elevated serum IgG4 level indicated the presence of IgG4-related disease. She was referred to the rheumatology department, where immunosuppression treatment was initiated. Oral mucosal grafting was performed to address the uncontrolled melting. At the follow-up examination, the melting was successfully controlled, the inflammation regressed, and the early hypertrophy of the oral mucosal epithelium flattened over time.ConclusionThis case highlights the potential for IgG4-related disease to manifest as atypical ocular surface involvement. Dry eye secondary to the disease can exacerbate existing findings. In such instances, preserving the integrity of the globe is of the utmost importance. Therefore, oral mucosal grafting, which is known for its durability, should be considered a viable option.

The spike protein (SP) is an outward-projecting transmembrane glycoprotein on viral surfaces. SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2), responsible for COVID-19 (Coronavirus Disease 2019), uses SP to infect cells that express angiotensin converting enzyme 2 (ACE2) on their membrane. Remarkably, SP has the ability to cross the blood-brain barrier (BBB) into the brain and cause cerebral damage through various pathomechanisms. To combat the COVID-19 pandemic, novel gene-based products have been used worldwide to induce human body cells to produce SP to stimulate the immune system. This artificial SP also has a harmful effect on the human nervous system.

Narrative review.

This narrative review presents the crucial role of SP in neurological complaints after SARS-CoV-2 infection, but also of SP derived from novel gene-based anti-SARS-CoV-2 products (ASP).

Literature searches using broad terms such as "SARS-CoV-2", "spike protein", "COVID-19", "COVID-19 pandemic", "vaccines", "COVID-19 vaccines", "post-vaccination syndrome", "post-COVID-19 vaccination syndrome" and "proteinopathy" were performed using PubMed. Google Scholar was used to search for topic-specific full-text keywords.

The toxic properties of SP presented in this review provide a good explanation for many of the neurological symptoms following SARS-CoV-2 infection and after injection of SP-producing ASP. Both SP entities (from infection and injection) interfere, among others, with ACE2 and act on different cells, tissues and organs. Both SPs are able to cross the BBB and can trigger acute and chronic neurological complaints. Such SP-associated pathologies (spikeopathies) are further neurological proteinopathies with thrombogenic, neurotoxic, neuroinflammatory and neurodegenerative potential for the human nervous system, particularly the central nervous system. The potential neurotoxicity of SP from ASP needs to be critically examined, as ASPs have been administered to millions of people worldwide.

For the diagnosis of immunoglobulin G4 (IgG4)-related dacryoadenitis and sialadenitis, either revised comprehensive diagnostic criteria or organ-specific diagnostic criteria for IgG4-related dacryoadenitis and sialadenitis in 2008 were applied; however, the collected knowledge for IgG4-related dacryoadenitis and sialadenitis required us to revise the criteria for IgG4-related dacryoadenitis and sialadenitis.

The board member of Japanese Study Group for IgG4-related Dacryoadenitis and Sialadenitis revised the diagnostic criteria for IgG4-related dacryoadenitis and sialadenitis. We collected the clinical questions to be revised and performed a review of the literature. When the data were insufficient, additional data collection was performed. After the revision, public comments were collected.

The three major points were revised. (1) Asymmetric or under two pairs of dacryoadenitis and sialadenitis were included as IgG4-related dacryoadenitis and sialadenitis. (2) The thresholds of IgG4-positive cell infiltration were adjusted to an IgG4+/IgG+ ratio >0.4 and IgG4+ cells >10 per high power field. (3) The labial salivary gland biopsy was allowed to diagnose IgG4-related dacryoadenitis and sialadenitis.

The revised diagnostic criteria for IgG4-related dacryoadenitis and sialadenitis solved several issues with the previous criteria. It will improve the early diagnosis of IgG4-related dacryoadenitis and sialadenitis, especially in situations without enough resources for a biopsy.

We aimed to report the characteristics of paediatric IgG4-related disease (IgG4-RD) through a multicentre registry, to assess disease clusters, and to evaluate the performances of the 2019 American College of Rheumatology and European League Against Rheumatism (ACR/EULAR) classification criteria and the 2020 revised comprehensive diagnostic (RCD) criteria in this cohort.

Data of IgG4-RD patients in 13 paediatric rheumatology centres were recorded to a web-based registration system. The diagnosis of IgG4-RD was made according to the 2011 comprehensive diagnostic criteria.

Thirty-five children (19 females and 16 males) with IgG4-RD were enrolled. The median age at diagnosis was 13.3 (25p-75p; 9.9-15.2) years. The most common organ involvement was the eye (n = 21, 60%), followed by lymph nodes (n = 12, 34.3%), musculoskeletal system (n = 12, 34.3%), and neurological system (n = 9, 25.7%). We identified three clusters in our study cohort: those with eye involvement (n = 11, 31.4%), those with eye involvement and neurological findings (n = 15, 42.9%), and those with pancreato-hepatobiliary disease and lymph node involvement (n = 9, 25.7%). Serum IgG4 levels were high in 19 out of 28 patients (67.8%). All patients except one received corticosteroid treatment, and azathioprine was the most preferred drug as a steroid-sparing agent. The sensitivities of the 2019 ACR/EULAR classification criteria and the 2020 RCD criteria were 5.7% and 88.5%, respectively.

IgG4-RD has a wide variety of clinical manifestations; however, in children, the most common presentation was orbital involvement. The 2020 RCD criteria had a better performance whereas the 2019 ACR/EULAR classification criteria performed poorly in paediatric patients.

IgG4-related disease (IgG4-RD) is a multi-organ fibroinflammatory condition often misdiagnosed due to its clinical similarities with other rheumatologic diseases such as Sjögren's syndrome (SS) and malignancy. This case highlights a 76-year-old woman with a complex medical history who presented with symptoms initially suggestive of SS but was ultimately diagnosed with IgG4-RD. The patient in our case report presented with bilateral, large, nontender submandibular lymphadenopathy. Initial serological tests were negative for SSA and SSB markers but revealed elevated immunoglobulin G levels of 2811 mg/dL. Imaging showed enlarged submandibular glands and lymphadenopathy. A core biopsy revealed a dense nodular lymphocytic infiltrate with variable parenchymal fibrosis and salivary gland acinar atrophy. The specimen was sent for further immunohistochemistry (IHC) testing as extended lab workup showed IgG4 levels of 843 mg/dL, raising concern for underlying IgG4-RD. IHC showed an increased number of IgG4 plasma cells, up to 50% in some areas, confirming the diagnosis of IgG4-RD. Treatment with prednisone led to rapid symptomatic improvement. Differentiating IgG4-RD from SS is challenging due to overlapping clinical and histological features. Elevated serum IgG4 levels (>135 mg/dL) are suggestive but not definitive for IgG4-RD; biopsy remains the gold standard for diagnosis. This case underscores the importance of considering IgG4-RD in patients presenting with SS-like symptoms, especially in the absence of anti-Ro/SSA and anti-La/SSB antibodies, and of initiating an extensive workup to fully delineate the extent of the disease in order to initiate timely treatment and prevent organ damage. This case report emphasizes the need for thorough evaluation in patients with SS-like symptoms to differentiate IgG4-RD, ensuring accurate diagnosis and effective treatment. Prompt recognition and management of IgG4-RD can improve patient outcomes and prevent long-term morbidity.

IgG4-related disease (IgG4-RD) is a highly heterogeneous autoimmune disease. Recently, 2 subtypes of IgG4-RD, proliferative and fibrotic, were defined according to patients' clinicopathologic characteristics. The purpose of this study was to determine the difference in fibroinflammatory activity shown on 68Ga-FAPI-04 and 18F-FDG PET/CT in the proliferative and fibrotic IgG4-RD subtypes. Methods: Thirty-seven newly diagnosed IgG4-RD patients (29 of the proliferative subtype and 8 of the fibrotic subtype) who had undergone 68Ga-FAPI-04 and 18F-FDG PET/CT were enrolled. SUVmax and target-to-background ratio (TBR) of IgG4-RD lesions were measured. To evaluate the weight of fibroinflammatory activity, the PET index of a lesion was calculated as the quotient of SUVmax or TBR of 68Ga-FAPI-04 and that of 18F-FDG. For the assessment of the global disease in an individual patient, the PET index was defined as the ratio of SUVmean of all involved lesions in 68Ga-FAPI-04 PET/CT to that in 18F-FDG. Results: The 18F-FDG uptake values of the most prominent lesions in the proliferative and fibrotic subtypes were similar; however, the proliferative subtype showed significantly higher uptake of 68Ga-FAPI-04 than did the fibrotic subtype (SUVmax, 17.67 ± 7.46 vs. 10.93 ± 2.22, P = 0.005; TBR, 15.49 ± 8.23 vs. 9.25 ± 3.00, P = 0.015). The PET index of proliferative-subtype patients was higher than that of fibrotic-subtype patients (1.46 ± 0.41 vs. 1.14 ± 0.39, P = 0.039). The PET index of pancreatobiliary disease was significantly higher than that of head-and-neck disease, fibrosis or aortitis, lymph nodes, and another disease subtype (P < 0.05). After first-line treatment, patients with a PET index of at least 1.5 had significantly shorter relapse-free survival than those with a PET index of less than 1.5 (22.0 mo vs. not reached, P < 0.0001; hazard ratio, 13.46; 95% CI, 2.236-81.03). Conclusion: The proliferative subtype of IgG4-RD had a greater weight of fibroinflammatory activity than that of the fibrotic subtype. The PET index, a marker of the weight of fibroinflammatory activity, is predictive of relapse-free survival of IgG4-RD.

The association between cancer and IgG4-related disease (IgG4-RD) is evolving. The primary aim of this study was to investigate the prevalence of malignancies in IgG4-RD. The secondary aim was to describe the epidemiological and clinical characteristics of IgG4-RD patients with a history of cancer.

Two hundred and ten patients with IgG4-RD were included in this retrospective study. IgG4-RD phenotypes, clinical and serological variables were analysed. The prevalence of cancer in IgG4-RD was compared with that in the Italian population using the registry of the Global Cancer Observatory (GCO) of the World Health Organization. The Standardized Incidence Ratio (SIR) for cancer in IgG4-RD was obtained based on the 5-year Limited Duration Prevalence (2015-2020) of tumours in the Italian population.

Thirty-seven/210 patients (18%) developed cancer before or after the diagnosis of IgG4-RD. Solid and haematologic tumours were more frequently observed in pancreato-biliary IgG4-RD. The SIR for malignancy in IgG4-RD patients was 2.54 higher than the general Italian population (P = 0.007). The SIR was 2.78 higher for males (P = 0.005) and 1.15 higher for females (P > 0.05). Thirty-two malignancies were diagnosed before and 16 after IgG4-RD diagnosis. Interval 'from IgG4-RD to cancer' was shorter than that 'from cancer to IgG4-RD'. Most tumours occurring after IgG4-RD developed within 36 months from diagnosis of IgG4-RD.

The prevalence of cancer in patients with IgG4-RD is increased compared with the Italian population and mechanistically suggests a possible paraneoplastic association. Close surveillance is warranted for the first 36 months after IgG4-RD diagnosis.

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.

To investigate the effects of thalidomide in preventing disease relapse with 'zero' glucocorticoids (GCs) usage in IgG4-related disease (IgG4-RD).

This was a multicentre, randomised, double-blinded, placebo-controlled study, in which eligible patients in disease active status were randomised into 2 groups (group 1: GCs+Thalidomide; group 2: GCs+Placebo) at a 1:1 ratio. The primary outcome of this trial was the disease relapse rate at month 12, whereas the secondary outcomes were the disease remission rate at month 12 and the incidence of adverse events (AEs).

A total of 60 patients were randomised, and 57 patients (GCs+Thalidomide: 29; GCs+Placebo: 28) finished the study per protocol. The relapse rates of the GCs+Thalidomide and GCs+Placebo groups at month 12 were 13.8% and 67.8%, respectively. A 100% response rate was observed in both treatment group, while the remission rates of the GCs+Thalidomide and GCs+Placebo groups were 75.8% and 32.1%, respectively. In total. 49 AEs were recorded in 35 participants, in which 4 were graded as moderate, and 45 were graded as mild. The risk-benefit analysis based on the evaluation of rates of disease relapse and moderate AEs within the 12-month follow-up showed a NNT (number needed to treat) of 2 and a NNH (number needed to harm) of 8 for thalidomide treatment.

Thalidomide can effectively prevent relapse in IgG4-RD outweighing its side effects, which indicating that thalidomide can be a potential safe therapeutic option for disease relapse prevention in parallel with steroid sparing in IgG4-RD.

Background/Objectives: IgG4-related disease (IgG4-RD) is a multi-organ disease with greatly varying therapeutic approaches and a lack of specific treatment algorithms. This systematic review aimed to determine the therapeutic approaches for pediatric IgG4-RD in real-word practice. Methods: We searched PubMed and Google Scholar for articles on pediatric IgG4-RD cases published in English from 2012 to August 2024, focusing on treatments and outcomes. Study type, treatment(s), dose/regimen, age and sex, organ(s) involved, and treatment outcomes were manually extracted from each study. Results: Of the 219 studies identified, we analyzed 81 studies, including 114 pediatric IgG4-RD cases. Fifty-seven percent of patients suffered from multi-organ disease and required several treatment schemes. Around 75% received steroids, alone or in combination, regardless of the organ affected. The treatment outcomes were positive in most cases, although relapses occurred in approximately 30% of patients, usually upon steroid tapering. Other common therapeutic approaches included immunosuppressants, often used as steroid-sparing agents, with azathioprine and mycophenolate mofetil being the most common; surgery for localized disease; and biologics, mainly rituximab, used in more severe/refractory cases. Uncommon but effective therapies included adalimumab and ruxolitinib. Drug combinations seemed to be more efficacious than monotherapies across studies. Patients > 10 years old more frequently received aggressive approaches (surgery and rituximab) and more often experienced relapses. Relapse rates were higher among females. Conclusions: This review highlights the use of systemic steroids as an effective first-line treatment for pediatric IgG4-RD, but also underscores the use of non-steroid-based alternatives in combination with steroids or other immunosuppressants for the effective management of IgG4-RD.

Allergic and autoimmune disorders are characterised by dysregulation of the immune responses to otherwise inert environmental substances and autoantigens, leading to inflammation and tissue damage. Their incidence has constantly increased in the last decades, and their co-occurrence defies current standards in patient care. For years, allergy and autoimmunity have been considered opposite conditions, with IgE and Th2 lymphocytes cascade driving canonical allergic manifestations and Th1/Th17-related pathways accounting for autoimmunity. Conversely, growing evidence suggests that these conditions not only share some common inciting triggers but also are subtended by overlapping pathogenic pathways. Permissive genetic backgrounds, along with epithelial barrier damage and changes in the microbiome, are now appreciated as common risk factors for both allergy and autoimmunity. Eosinophils and mast cells, along with autoreactive IgE, are emerging players in triggering and sustaining autoimmunity, while pharmacological modulation of B cells and Th17 responses has provided novel clues to the pathophysiology of allergy. By combining clinical and therapeutic evidence with data from mechanistic studies, this review provides a state-of-the-art update on the complex interplay between allergy and autoimmunity, deconstructing old dichotomic paradigms and offering potential clues for future research.

Background: IgG4-related disease is a rare, chronic inflammatory disorder characterized by lymphoplasmacytic infiltration, 'storiform' fibrosis, and elevated IgG4 levels in affected tissues. This disease has a broad and heterogeneous clinical spectrum that includes four main phenotypes: pancreatic-hepatobiliary disease, retroperitoneal/aortic fibrosis, head and neck disease, and Mikulicz syndrome. Case Description: An 85-year-old male patient with a clinical presentation, which is unusual outside Asia, of IgG4-related disease phenotype Mikulicz syndrome, characterized by bilateral dacryoadenitis, orbital pseudotumor, and no evidence of significant systemic participation. Despite extensive involvement in the orbital and glandular region, the patient did not develop serious organ complications, a behavior rarely documented in the literature. Despite the serum IgG4 levels being normal (<135 mg/dL), the clinical and radiological picture suggested IgG4-RD, emphasizing the need for a biopsy for a definitive diagnosis. Histopathological examination revealed a dense lymphoplasmacytic infiltrate, storiform fibrosis, and more than 40% IgG4-positive cells, confirming the diagnosis. Results: Treatment with prednisone was initiated alongside azathioprine for long-term control. Calcium and vitamin D3 supplementation were added to prevent glucocorticoid-induced osteoporosis. Remarkable clinical improvement was observed within 24 h, with progressive orbital and glandular symptoms resolution. Over a year, the patient exhibited complete resolution of the orbital tumors, total recovery of vision, and no relapses. The only sequelae observed were dry eye. Conclusions: This case highlights the need to consider IgG4-RD with normal serum IgG4 levels, the importance of histopathology for diagnosis, and the efficacy of steroids as first-line treatment. A multidisciplinary approach is essential for timely treatment.

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.

IgG4-related disease (IgG4-RD) is a relapsing-remitting, fibroinflammatory, multisystem disorder. Cardiovascular involvement from IgG4-RD has not been systematically characterised. In this study, we sought to evaluate consecutive patients with IgG4-RD using a detailed multiparametric cardiovascular magnetic resonance (CMR) imaging protocol.

We prospectively enrolled 11 patients with histology-confirmed IgG4-RD; with active disease at time of scan. We undertook a detailed multiparametric CMR imaging protocol at 1.5T including cine imaging, native T1 and T2 mapping, stress perfusion imaging with inline quantitation of myocardial blood flow and late gadolinium enhancement (LGE) imaging.

All patients exhibited at least one abnormality on CMR imaging. Abnormal elevation of global or segmental left ventricular myocardial T1 and T2 values was present in four patients, suggesting myocardial oedema or inflammation. Abnormal LGE, suggesting myocardial scar fibrosis, was present in nine patients, with eight displaying a non-ischaemic pattern, and one showing an ischaemic pattern. Four patients fulfilled both Lake Louise Criteria for active myocardial inflammation, while a further six fulfilled one criterion. Myocardial perfusion reserve was normal in all evaluable patients. Ten patients had normal ventricular volumes, mass and systolic function. In addition, thoracic aortitis was identified in three patients who underwent 18F-flourodeoxyglucose PET/CT imaging, with resolution following anti-B-cell treatment.

In this cohort of patients with histology-confirmed IgG4-RD, multiparametric CMR revealed no changes in gross cardiac structure and function, but frequent myocardial tissue abnormalities. These data suggest a plausible pathophysiological link between IgG4-RD and cardiovascular involvement.

IgG4-related disease is a rare fibroinflammatory condition. Prompt recognition is fundamental to initiate treatment and to prevent organ damage. Diagnostic and classification criteria are primarily intended for use by clinicians with established expertise in IgG4-related disease. Absence of disease awareness among primary care physicians and specialists without expertise in IgG4-related disease remains the main cause of diagnostic delay. We aimed to identify red flags that might increase the suspicion of IgG4-related disease in primary and secondary care settings. A task force of experts in IgG4-related disease from the European Reference Network for Rare Connective Tissue Diseases (ERN-ReCONNET), patient representatives, and primary care physicians derived potential red flags for IgG4-related disease through a systematic literature search and a level of agreement exercise. Five red flags reached 100% agreement among experts: swelling in one or more organ system; pancreatic and biliary tree involvement; increased serum IgG4; IgG4+ plasma cell tissue infiltration; and obliterative phlebitis. Red flags for IgG4-related disease are intended for use in primary and secondary care to improve referral to centres of expertise and prompt early diagnosis.

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated disorder characterized by elevated serum IgG4 levels and the enlargement and fibrosis of organs. As a rare manifestation, coronary arteries can be affected by IgG4-RD as coronary periarteritis, leading to serious complications such as stenosis or aneurysm. Although coronary periarteritis poses a life-threatening condition, optimal treatment strategies remain unclear due to its extreme rarity. While glucocorticoids have shown efficacy in several reported cases of IgG4-related coronary periarteritis, many cases experience relapse during glucocorticoid tapering. Furthermore, long-term use of glucocorticoids promotes atherosclerosis and increases the risk of major adverse cardiovascular events. Given that rituximab has been reported to be effective in treating IgG4-RD, it may be a potential treatment option for this condition. We present a case of IgG4-related coronary periarteritis, in which the patient achieved and maintained remission with rituximab. Furthermore, our review of the literature identified 17 cases of IgG4-related coronary periarteritis, all of which were successfully treated with rituximab. These findings suggest that rituximab serves as a viable option for both induction and maintenance therapy in IgG4-related coronary periarteritis.

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue. IgG4 is the least naturally abundant IgG subclass, and the hallmark feature of IgG4-RD is markedly increased IgG4-positive plasma cells (with an IgG4 to IgG ratio >40%) in affected tissue, along with elevated polyclonal serum IgG and IgG4 in most patients. Histological diagnosis is essential, and other key features include storiform fibrosis, lymphoplasmacytic infiltrate, tissue eosinophilia, and obliterative phlebitis. The disease can present with predominantly proliferative features, such as swollen lacrimal and salivary glands, orbital pseudotumor, autoimmune pancreatitis, polyclonal hypergammaglobulinemia (PHGG), eosinophilia, and tubulointerstitial nephritis of the kidneys, or predominantly fibrotic disease, including mediastinal and retroperitoneal fibrosis, sclerosing mesenteritis, and hypertrophic pachymeningitis. This review focuses on 4 key hematological manifestations: PHGG, IgG4-positive plasma cell enriched lymphadenopathy (LAD), eosinophilia, and retroperitoneal fibrosis (RPF). These features are found in 70%, 60%, 40%, and 25% of IgG4-RD patients, respectively, but can also represent key hematological "mimickers" of IgG4-RD, including Castleman disease (PHGG, LAD), eosinophilic vasculitis (eosinophilia, PHGG, LAD), hypereosinophilic syndromes (eosinophilia, LAD, PHGG), and histiocyte disorders (PHGG, LAD, RPF). An organized approach to these 4 manifestations, and how to distinguish IgG4-RD from its mimickers, is explained. Proliferative manifestations typically respond very well to treatment corticosteroids, rituximab, and other immunosuppressives, whereas chronic fibrotic disease may not be reversible with current treatment modalities.

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.

We started a registry for cases of immunoglobulin (Ig)G4-related disease (IgG4-RD) in December 2019 to clarify the clinical profile of IgG4-RD. In this study, clinical information from 854 cases registered by February 16, 2024 was analyzed from multiple perspectives. Diagnosis of IgG4-RD was made in 808 cases, comprising 638 definite, 38 probable, and 132 possible. The mean ± SD age at time of enrollment of the 808 cases was 67.9 ± 11.3 years, with 68.8% being male. The pancreas was the most frequently affected organ (49.8%), followed by the submandibular glands (46.2%) and lacrimal glands (30.6%). This study reconfirmed the pancreas and head-and-neck region as major affected areas in IgG4-RD. Clinically, submandibular adenitis and autoimmune pancreatitis often occur together in the same patient, but no association between the two organs was observed in our analysis. Regarding diagnosis, the comprehensive diagnostic criteria were most commonly used (63.6%). Storiform fibrosis and phlebitis obliterans were detected at different frequencies in different organs. In summary, this registry study identified clinical, imaging, hematologic, and pathologic findings in 808 Japanese patients with IgG4-RD. The frequency of affected organs and their characteristic pathological findings will be particularly useful for future practice.

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).

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.

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).

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.

Research on IgG4-related disease (IgG4-RD), an autoimmune condition recognized to be a unique disease entity only two decades ago, has processed from describing patients' symptoms and signs to summarizing its critical pathological features, and further to investigating key pathogenic mechanisms. Challenges in gaining a better understanding of the disease, however, stem from its relative rarity-potentially attributed to underrecognition - and the absence of ideal experimental animal models. Recently, with the development of various high-throughput techniques, "omics" studies at different levels (particularly the single-cell omics) have shown promise in providing detailed molecular features of IgG4-RD. While, the application of omics approaches in IgG4-RD is still at an early stage. In this paper, we review the current progress of omics research in IgG4-RD and discuss the value of machine learning methods in analyzing the data with high dimensionality.

To investigate the potential utility of quantitative parameters obtained by 18F-fibroblast activation protein inhibitor positron emission tomography/computed tomography ([18F]AlF-NOTA-FAPI-04 PET/CT) in the assessment of organ involvement and disease activity in IgG4-related disease (IgG4-RD).

This study enrolled patients who underwent [18F]AlF-NOTA-FAPI-04 PET/CT scans at the Department of Rheumatology, The First Affiliated Hospital, Zhejiang University School of Medicine from August 2021 to August 2022. The PET/CT images of the included patients were re-evaluated by PET center technicians, and the maximal standardized uptake value (SUVmax), metabolic lesion volume (MLV), and total lesion FAPI (TL-FAPI) were used to evaluate the involved organs and tissues that abnormally accumulated [18F]AlF-NOTA-FAPI-04. The clinical and laboratory data of patients are also systematically collected and analyzed.

Among the patients included in this study, 12 patients met the IgG4-RD classification criteria established by the American College of Rheumatology in 2019. Among them, 8 were males and 4 were females, with an average age of 59.3 ± 11.5 years. 50% of IgG4-RD patients were found with more organ involvement on PET/CT than physical examination, ultrasonography, and computed tomography. IgG4 levels (Rho = 0.594, p = 0.042) and IgG4-RI (Rho = 0.647, p = 0.023) were significantly positively correlated with TL-FAPI. After linear regression analysis, only TL-FAPI showed a predictive value of RI (R2 = 0.356, B = 0.008, p = 0.041).

[18F]AlF-NOTA-FAPI-04 PET/CT is a useful tool for identifying asymptomatic organ involvement and assessing disease activity. The TL-FAPI as an indicator was positively correlated with IgG4-RD disease activity.

Many aspects of IgG4-related diseases were initially described during the late 19th and early 20th century. A variety of clinical presentations caused by this common pathology have been named after the researchers who first described the disorders, such as Mikulicz, Küttner, Riedel or Ormond. However, the initial description of retroperitoneal fibrosis dates back to even 50 years earlier, when in 1846, the Prussian private practitioner Raphael Jakob Kosch described a hitherto unknown constellation of symptoms and pathological findings in a famous patient. This celebrity was the mathematician and astronomer Friedrich Wilhelm Bessel, a close friend of Alexander von Humboldt and Carl Friedrich Gauss.

Immunoglobulin G4-related ophthalmic disease (IgG4-ROD) poses clinical challenges due to its heterogeneous ocular and systemic manifestations. We aim to report the systemic involvement and the clinical, serological and radiological associations of a cohort of Chinese patients.

A territory-wide, biopsy-proven, Chinese cohort. A retrospective, masked chart review of medical records, orbital images, and histopathology reports.

A total of 122 (65 male) patients with a follow-up of 81 ± 49 (24 to 84) months were reviewed. Ninety (74%) patients presented bilaterally. Subacute upper eyelid swelling was the commonest presentation (82/122, 67%). During follow-up, 91/122 patients (75%) underwent extra-orbital imaging including computer tomography (692 films), ultrasonography (182 films), magnetic resonance imaging (76 films) and whole body FDG-PET scan (33 films). Eighty-six (95%) of these 91 patients had extra-orbital involvement radiologically (2.7 ± 1.6 regions, range: 0 to 9). Lymph node was the most prevalent (N = 60,66%), followed by salivary gland (N = 51,56%), lung (N = 49,54%), kidney (N = 22, 24%), hepatobiliary tree (N = 18, 20%) and pancreas (N = 17, 19%). Other organs include thyroid, aorta, meninges/brain and skin. Twenty-eight (23%) patients had allergic diseases (19 asthma, 16 allergic rhinitis, and 6 eczemas). Fifty-seven (48%) patients had paranasal sinusitis. Serum eosinophilia was associated with a higher number (3.24 versus 2.52, P = 0.0304) of organ involvement. Patients with deep organ involvement was associated with a higher age of IgG4-ROD onset (70 ± 12 versus 56 ± 13, P < 0.0001).

95% of the patients who underwent systemic imaging in our cohort had systemic organ involvement. An early physicians' assessment and radiological imaging are recommended after the diagnosis of IgG4-ROD.

Immunoglobulin G4-related ophthalmic disease (IgG4-ROD) is an emerging, immune-mediated fibroinflammatory orbital disease, characterized by tumefactive lesions with noticeable IgG4+ plasma cell infiltration and distinctive pathohistological features. This disease is often associated with elevated serum IgG4 concentrations. IgG4-ROD may affect any ophthalmic tissues, particularly the lacrimal gland, extraocular muscles, and trigeminal nerves. Although the exact pathogenic role of IgG4 antibodies remains unclear, B-cell depleting agents have been reported to be an effective treatment. The diverse clinical manifestations of IgG4-ROD complicate diagnosis, and without prompt treatment, visual-threatening complications such as optic neuropathy may arise. Recent advances in understanding and managing IgG4-ROD have revolutionized the diagnosis and treatment of this emerging disease. This review article aims to provide a comprehensive overview of the latest advancements in the field of IgG4-ROD.

IgG4-related disease (IgG4-RD) is a systemic immune-mediated disease that can involve nearly any organ. IgG4-RD can affect the kidney in different disease patterns, collectively referred to as IgG4-related kidney disease (IgG4-RKD).

We conducted a tissue-based cohort study with clinicopathological correlation in 125 patients with IgG4-RKD.

The mean age at biopsy (n = 120) or nephrectomy (n = 5) was 63 years; 80% were male. One hundred eighteen patients (94%) had IgG4-related tubulointerstitial nephritis (IgG4-TIN); 20 patients (16%) had IgG4-related membranous glomerulonephritis (IgG4-MGN; 13 with concurrent IgG4-TIN). The primary clinical indication for biopsy/nephrectomy was acute or chronic renal failure in 78%, proteinuria in 17%, and mass lesion(s) in 15% (with overlap in primary indication). Fifty-two percent patients (41/79) had abnormal radiographic findings, including masses in 30% (24/79). All patients with IgG4-MGN had proteinuria. Extrarenal involvement by IgG4-RD was present in 79%. Median serum creatinine at presentation was 2.5 mg/dl (range 0.7-12). Serum IgG and/or IgG4 was increased in 91% (53/58); hypocomplementemia was present in 56% (43/77). Light microscopy showed plasma cell-rich interstitial nephritis in all cases of IgG4-TIN. Ninety-two percent of patients showed increased IgG4+ plasma cells. Seven percent showed an acute interstitial nephritis (AIN) pattern, and 5% showed non-necrotizing arteritis. Tubular basement membrane immune deposits were present in 83% of IgG4-TIN. Treatment information was available for 71 patients; 62 were treated with immunosuppression. Of those with elevated creatinine, 72% (41/57) showed a treatment response.

This largest tissue-based series more clearly defines the disease phenotype of IgG4-RKD.

Our study aimed to investigate the distinct clinical patterns of seronegative IgG4-related disease (IgG4-RD) patients.

We retrospectively enrolled 698 treatment-naïve IgG4-RD patients in this study. Patients were divided into four different subgroups according to their baseline serum IgG4 levels. The distinct clinical patterns of seronegative IgG4-RD patients were revealed through the comparison of baseline clinical data and disease prognosis among the different subgroups. COX regression analyses were used to investigate the risk factors for disease relapse and to construct the nomogram model.

Seronegative IgG4-RD patients account for a minority of IgG4-RD patients (49/698, 7.02%). The proportions of seronegative IgG-RD patients in our study and several Asian cohorts were significantly lower than those of the European and American cohorts. Seronegative IgG4-RD patients got lower serum IgG levels (p < 0.0001), lower eosinophil count (p < 0.0001), lower serum IgE levels (p < 0.0001)), lower IgG4-RD responder index (RI) scores (p < 0.0001), and fewer affected organ numbers (p < 0.0001) compared with other subgroups, whereas they were more likely to manifest fibrotic type with some special organ involvement. Younger age at onset, GCs monotherapy, elevated C-reactive protein level, and elevated erythrocyte sedimentation rate level are the risk factors for the disease relapse of seronegative IgG4-RD patients. An effective nomogram model predicting disease relapse of seronegative IgG4-RD patients was constructed. Seronegative IgG4-RD patients with scores >84.65 at baseline were susceptible to suffering from disease relapse.

Distinct clinical features and multiple risk factors for disease relapse of seronegative IgG4-RD patients have been revealed in this study. A nomogram model was constructed to effectively predict disease relapse during the follow-up period.

Mass-forming phenotypes of IgG4-related disease (IgG4-RD) mimic malignancy and histological confirmation can be challenging. A woman in her 70s with HIV infection presented with painless obstructive jaundice and weight loss. Magnetic resonance imaging was suggestive of unresectable cholangiocarcinoma. Tumour markers and serum IgG4 were normal. Percutaneous liver biopsy was consistent with IgG4-RD inflammatory pseudotumour, with complete response to glucocorticoid therapy. Two years later, a new episode of obstructive jaundice occurred, with CT showing a solid lesion in the head of the pancreas with double duct sign and encasement of the portal vein. Re-induction therapy was tried without response. Fine-needle biopsy was consistent with pancreatic cancer. Supportive care was offered and the patient died 8 months later, with no signs of disease progression on subsequent imaging. We discuss the challenges of IgG4-RD diagnosis and treatment and the differential diagnosis between mass-forming phenotypes and malignancy, highlighting the difficulties in managing such patients.