IgG4-related disease

Immunoglobulin G4-related spinal pachymeningitis: A case report

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a complex immune-mediated condition that causes fibrotic inflammation in several organs. A significant clinical feature of IgG4-RD is hypertrophic pachymeningitis, which manifests as inflammation of the dura mater in intracranial or spinal regions. Although IgG4-RD can affect multiple areas, the spine is a relatively rare site compared to the more frequent involvement of intracranial structures.

CASE SUMMARY

A 70-year-old male presented to our hospital with a two-day history of fever, altered mental status, and generalized weakness. The initial brain magnetic resonance imaging (MRI) revealed multiple small infarcts across various cerebral regions. On the second day after admission, a physical examination revealed motor weakness in both lower extremities and diminished sensation in the right lower extremity. Electromyographic evaluation revealed findings consistent with acute motor sensory neuropathy. Despite initial management with intravenous immunoglobulin for presumed Guillain-Barré syndrome, the patient exhibited progressive worsening of motor deficits. On the 45^th day of hospitalization, an enhanced MRI of the entire spine, focusing specifically on the thoracic 9 to lumbar 1 vertebral level, raised the suspicion of IgG4-related spinal pachymeningitis. Subsequently, the patient was administered oral prednisolone and participated in a comprehensive rehabilitation program that included gait training and lower extremity strengthening exercises.

CONCLUSION

IgG4-related spinal pachymeningitis, diagnosed on MRI, was treated with corticosteroids and a structured rehabilitation regimen, leading to significant improvement.

New insights into predictors of autoimmune pancreatitis relapse after steroid therapy

OBJECTIVES

While autoimmune pancreatitis (AIP) responds well to steroid therapy, the high relapse rate in type 1 AIP remains a critical problem. The present study examined predictors of relapse of type 1 AIP following steroid therapy.

MATERIALS AND METHODS

Nine factors potentially predictive of relapse were analyzed in 81 AIP patients receiving steroid therapy with follow-up ≥ 12 months. The rate of serum IgG4 decrease following steroid therapy was calculated by dividing the difference between serum IgG4 values before and at two months after the start of steroid by the IgG4 value before steroid.

RESULTS

A relapse occurred in 11 patients (13.5%) during a median of 38 months. Multivariate analysis revealed that the presence of IgG4-related retroperitoneal fibrosis (HR: 5.59; 95% CI: 1.42-22.0; p = 0.014) and the low rate of serum IgG4 decrease after steroid therapy (HR: 0.048; 95% CI: 0.005-0.46; p = 0.008) were significant, independent predictors of AIP relapse. The cut-off value based on receiver operating characteristic curve data for the rate of serum IgG4 decrease before and at two months after steroid therapy distinguishing patients with and without a relapse was 0.65. Using this cut-off value, the area under the curve, sensitivity, and specificity were found to be 0.63, 0.73, and 0.60, respectively.

CONCLUSION

The low rate of serum IgG4 decrease after the start of steroid therapy and the presence of IgG4-related retroperitoneal fibrosis were predictive of type 1 AIP relapse. Cautious, gradual tapering of steroid dosage and longer maintenance therapy are recommended for patients with these factors.

Factors related to elevated serum immunoglobulin G4 (IgG4) levels in a Japanese general population

BACKGROUND

Elevated serum immunoglobulin G4 (IgG4) concentrations are one of the characteristic findings in IgG4-related disease (IgG4-RD). This study investigated the frequency of elevated serum IgG4 levels and associated factors in a general Japanese population.

METHODS

Serum IgG4 concentrations were measured in 1,201 residents of Ishikawa prefecture who underwent general medical examinations. Factors associated with elevated serum IgG4 concentrations were assessed by logistic regression analysis. Participants with elevated serum IgG4 were subjected to secondary examinations.

RESULTS

The mean serum IgG4 concentration was 44 mg/dL, with 42 (3.5%) participants having elevated serum IgG4 levels. Age- and sex-adjusted logistic regression analyses showed that male sex, older age, and lower intake of lipids and polyunsaturated fatty acids and higher intake of carbohydrates in daily diet were associated with elevated serum IgG4 concentration. Subgroup analyses in men showed that older age, lower estimated glomerular filtration rates based on serum cystatin C (eGFR-cysC) levels, and higher hemoglobin A1c (HbA1c) levels were associated with elevated serum IgG4 concentration. Analyses in women showed that lower intake of lipids and fatty acids and higher intake of carbohydrates were significantly associated with elevated serum IgG4 concentration. One of the 15 participants who underwent secondary examinations was diagnosed with possible IgG4-related retroperitoneal fibrosis.

CONCLUSIONS

Elevated serum IgG4 levels in a Japanese general population were significantly associated with older age, male gender, and dietary intake of nutrients, with some of these factors identical to the epidemiological features of IgG4-RD.

Microbe-associated molecular patterns derived from fungi and bacteria promote IgG4 antibody production in patients with type 1 autoimmune pancreatitis

Enhanced IgG4 antibody (Ab) response is a prominent feature of type 1 autoimmune pancreatitis (AIP). Innate immune responses associated with IgG4 Ab production are poorly defined. We have previously reported that peripheral blood mononuclear cells (PBMCs) isolated from patients with type 1 AIP produce large amounts of IgG4 Abs upon stimulation with bacterial cell wall components. In addition, we showed that activation of plasmacytoid dendritic cells producing interferon (IFN)-α, interleukin (IL)-33, and B cell-activating factor (BAFF) upon sensing intestinal bacteria mediates the development of experimental AIP. In this study, we attempted to clarify the role of innate immunity against fungi in inducing enhanced IgG4 Ab responses in type 1 AIP. PBMCs isolated from healthy controls and patients with type 1 AIP were stimulated with a broad range of bacterial and fungal cell wall components. The concentrations of IgG1, IgG4, and cytokines were measured using enzyme-linked immunosorbent assays. Cell wall components derived from bacteria and fungi induced IgG1 and IgG4 Ab production in patients with type 1 AIP. Various types of microbe-associated molecular pattern motifs enhanced IgG4 Ab production in patients with type 1 AIP compared with the limited motifs in healthy controls. The enhanced IgG1 and IgG4 Ab production that followed in response to bacterial and fungal cell wall components was parallel to that of IFN-α, IFN-γ, IL-10, IL-33, and BAFF. In conclusion, cell wall components derived from fungi as well as bacteria promote IgG4 Ab responses in patients with type 1 AIP.

Efficacy and safety of rituximab induction therapy and effect of rituximab maintenance for IgG4-related disease: a systematic review and meta-analysis

BACKGROUND

Previous studies have reported that rituximab (RTX) therapy might be beneficial in reducing relapse rates in patients with IgG4-related disease (IgG4-RD). Therefore, we aimed to systematically assess the efficacy and safety of RTX induction treatment and the effect of RTX maintenance in patients with IgG4-RD.

METHODS

The protocol was registered in the PROSPERO (CRD42023427352). PubMed, Embase, the Cochrane database, Scopus, and the Web of Science were interrogated to identify studies that evaluated the impact of RTX on prognosis in IgG4-RD. We explored the impact of various subgroups of factors on relapse outcomes and focused on the possible role of maintenance therapy in reducing relapse rates. The pooled incidence of adverse events of RTX therapy and the influencing factors have also been evaluated.

RESULTS

Eighteen studies comprising 374 patients (mean age 56.0 ± 8.7 years; male 73.7 %) with a mean follow-up duration of 23.4 ± 16.3 months were included. The pooled estimate of the response rate, complete remission rate, overall relapse rate, adverse event rate, and serious adverse event rate of RTX induction therapy were 97.3 % (95 % CI, 94.7 %-99.1 %), 55.8 % (95 % CI, 39.6 %-71.3 %), 16.9 % (95 % CI, 8.7 %-27.1 %), 31.6 % (95 % CI, 16.7 %-48.9 %) and 3.9 % (95 % CI, 0.8 %-8.9 %), respectively. In subgroup analysis, the pooled relapse rate was significantly lower in studies with maintenance than without maintenance (2.8% vs 21.5 %, p < 0.01). Pooled Kaplan-Meier relapse curves also demonstrated that RTX maintenance therapy provided a better prognosis.

CONCLUSIONS

RTX induction therapy appears to have satisfactory efficacy in the induction of remission in IgG4-RD. In addition, prophylactic RTX maintenance therapy after induction may be beneficial in preventing relapse of IgG4-RD.

Rare genetic variants provide a mechanistic basis for immune imbalance in IgG4-related disease

Autoimmune diseases are commonly associated with a polygenic inheritance pattern. In rare instances, causal monogenic variants have been identified. The study by Liu et al. in this issue of the JCI provides an example of monogenic variants occurring in patients with IgG4-related disease (IgG4-RD). The authors investigated a familial cluster of IgG4-RD that consisted of an affected father and two daughters; the mother was unaffected. Genome sequencing of this quad identified a variant in IKZF1 (encoding IKAROS) and another variant in UBR4 (encoding E3 ubiquitin ligase). Both variants were present in the father and both daughters but absent in the unaffected mother. Using multidimensional profiling of immune cells and functional experiments in primary cells, the authors determined a molecular pathway contributing to T cell activation in IgG4-RD. Importantly, the characterization of these variants provides insights into pathogenic mechanisms in IgG4-RD and, potentially, other autoimmune diseases.

Characteristics of imaging in hepatic inflammatory pseudotumors: a comparison between IgG4-related and IgG4-unrelated cases

OBJECTIVES

The objective of this study was to examine the imaging features of hepatic inflammatory pseudotumors (IPTs) associated with IgG4-related and IgG4-unrelated conditions and to enhance the approach toward distinguishing between these two types of IPTs.

METHODS

A retrospective study was conducted, involving 20 patients diagnosed with hepatic IPTs. Imaging procedures were conducted within a timeframe of 4 weeks prior to hepatectomy or biopsy. The imaging features were then analyzed and compared using chi-squared analysis.

RESULTS

Seventeen (81.0%) IPTs were located in the hepatic subcapsular area; six (66.7%) IgG4-related IPTs were distributed around the hepatic hilum; and eleven (91.7%) IgG4-unrelated and three (33.3%) IgG4-related IPTs had unclear boundaries. All lesions exhibited similar characteristics in CT scans, T1-weighted imaging (T1WI), T2-weighted imaging (T2WI), and diffusion-weighted imaging (DWI), with the apparent diffusion coefficient (ADC) values slightly higher than the surrounding liver tissue. Delayed hypoenhancement, observed in five cases (55.6%), was exclusively present in IgG4-related IPTs. The remaining IPT lesions displayed progressive enhancement, septal and marginal enhancement, and persistent enhancement. Central enhancement was absent in three IgG4-related IPTs (33.3%) and ten IgG4-unrelated IPTs (83.3%). The duct-penetrating sign was identified in two IgG4-unrelated IPTs (16.7%) and seven IgG4-related IPTs (77.8%). Furthermore, seven patients with IgG4-related IPTs had additional lesions outside the liver.

CONCLUSIONS

IgG4-related lesions are frequently found in the vicinity of the hepatic hilum; they display the duct-penetrating sign and affect other organs as well. Both groups exhibited progressive or persistent contrast enhancement in typical IPT lesions, but delayed hypoenhancement was only observed in the IgG4-related IPT group. IgG4-unrelated IPT lesions often exhibited indistinct boundaries lacking central enhancement.

CRITICAL RELEVANCE STATEMENT

Differences in imaging features differentiate IgG4-related and -unrelated inflammatory pseudotumors (IPT). IgG4-related lesions are frequently near the hepatic hilum, display duct-penetrating sign, and affect other organs. Only the IgG4-related group demonstrated delayed hypoenhancement. IgG4-unrelated IPT lesions often exhibited indistinct boundaries lacking central enhancement.

KEY POINTS

Compared with IgG 4-unrelated IPTs, IgG4-related IPTs show delayed hypoenhancement and affect other organs. IgG4-unrelated IPTs have unclear boundaries and lack central enhancement. Improved IPT diagnostic capabilities can help minimize additional, potentially unnecessary, interventions.

Revealing the distinct clinical patterns and relapse risk factors in seronegative IgG4-RD patients: A retrospective cohort study over a decade

OBJECTIVES

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

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

IgG4-related disease in the pelvis: A mimicker of gynecologic malignancy

This report describes a unique case of IgG4-related disease in a 36-year-old woman who presented with a pelvic mass. Although CT and MR imaging initially suggested a malignant process, further work-up including sigmoidoscopy and surgical exploration revealed no evidence of malignancy. The final pathology indicated an inflammatory process, leading to the diagnosis of IgG4-related disease. After receiving appropriate systemic treatment, the patient's symptoms significantly improved. This case underscores the limitations of current imaging studies and emphasizes the importance of considering a wide range of potential diagnoses when dealing with pelvic masses of uncertain etiology.

Systematic analysis for clinical characteristics and outcomes of IgG4-related disease patients during the COVID-19 pandemic

BACKGROUND

To systematically describe clinical characteristics and investigate factors associated with COVID-19-related infection, hospital admission, and IgG4-related disease relapse in IgG4-RD patients.

METHODS

Physician-reported IgG4-RD patients were included in this retrospective study. Using multivariable logistic regression analysis to determine factors for primary outcome (COVID-19-related IgG4-RD relapse) and secondary outcome (COVID-19-related infection and hospital admission). Covariates included age, sex, body mass index, smoking status, comorbidities, IgG4-RD clinical features, and treatment strategies.

RESULTS

Among 649 patients, 530 had a diagnosis of COVID-19, 25 had COVID-19-related hospital admission, and 69 had COVID-19-related IgG4-RD relapse. Independent factors associated with COVID-19 infection were age (OR, 0.98; 95% CI, 0.96-1.00), body mass index (1.10, 1.03-1.18), and tofacitinib (0.34, 0.14-0.79). Further analysis indicated that age (1.10, 1.03-1.16), coronary heart disease (24.38, 3.33-178.33), COVID-19-related dyspnea (7.11, 1.85-27.34), pulmonary infection (73.63, 16.22-4615.34), and methotrexate (17.15, 1.93-157.79) were associated with a higher risk of COVID-19-related hospital admission. Importantly, age (0.93, 0.89-0.98), male sex (0.16, 0.03-0.80), ever/current smoking (19.23, 3.78-97.80), COVID-19-related headache (2.98, 1.09-8.17) and psychiatric symptoms (3.12, 1.07-9.10), disease activity before COVID-19 (1.89, 1.02-3.51), number of involved organs (1.38, 1.08-1.76), glucocorticoid dosage (1.08, 1.03-1.13), and methotrexate (5.56, 1.40-22.08) were strong factors for COVID-19-related IgG4-RD relapse.

CONCLUSIONS

Our data add to evidence that smoking and disease-specific factors (disease activity, number of involved organs, and specific medications) were risk factors of COVID-19-related IgG4-RD relapse. The results highlight the importance of adequate disease control with b/tsDMARDs, preferably without using methotrexate and increasing glucocorticoid dosages in the COVID-19 era. Key Points • COVID-19-related infection or hospital admission were associated with known general factors (age, body mass index, specific comorbidities and methotrexate) among IgG4-RD patients. • Smoking and disease-specific factors (disease activity, number of involved organs and specific medications) were associated with higher odds of COVID-19-related IgG4-RD relapse. • The results highlight the importance of adequate disease control with b/tsDMARDs, preferably without using methotrexate or increasing glucocorticoid dosages.

Endoscopic Retrograde Cholangiopancreatography-Related Procedures for the Differential Diagnosis of Isolated Immunoglobin G4-Related Sclerosing Cholangitis and Perihilar Cholangiocarcinoma

BACKGROUND/PURPOSE

Differential diagnosis of isolated immunoglobin (Ig)G4-related sclerosing cholangitis (IgG4-SC) and cholangiocarcinoma is challenging. We aimed to clarify the role of endoscopic retrograde cholangiography (ERCP)-related procedures in the differential diagnosis of isolated IgG4-SC and perihilar cholangiocarcinoma (PHCC).

METHODS

Seven patients with hilar-type isolated IgG4-SC diagnosed at Hiroshima University Hospital and sixty-five patients with surgically resected invasive PHCC were enrolled, and the diagnostic yields of intraductal ultrasonography (IDUS), peroral cholangioscopy (POCS), and pathological examinations were determined.

RESULTS

In six of seven (86%) patients with isolated IgG4-SC, the stricture was in the perihilar bile duct. IDUS showed that symmetrical wall thickening (40% vs. 5%, p = 0.04), homogeneous internal echo (80% vs. 5%, p < 0.001), and smooth outer margins (80% vs. 6%, p < 0.001) were more frequent in isolated IgG4-SC than in PHCC. POCS showed a smooth mucosal surface more frequent in isolated IgG4-SC (75% vs. 7%, p = 0.006). Only one patient had two pathological findings characteristic of IgG4-SC. The sensitivity for diagnosing PHCC was 81% using two or more combined sampling methods.

CONCLUSIONS

Pathological examinations have limitations in the differential diagnosis of isolated-IgG4-SC and PHCC, and a diagnostic strategy that combines multiple ERCP-related procedures, including IDUS and POCS, is recommended.

Toll-like receptors 2 and 4, and bacterial proteins in IgG4-related sialadenitis, other types of chronic sialadenitis and sialolithiasis

Background

The association of chronic sclerosing sialadenitis and IgG4-related disease (IgG4-RD) has resulted in the more frequent identification of IgG4-positivity in submandibular gland inflammations, also uncovering IgG4 overexpression in nonspecific inflammations. These findings lead us to hypothesise that IgG4-positive sialadenitis represents a continuous inflammatory process overlapping histologically with IgG4-RD, possibly differing in aetiology. However, the antigen underlying IgG4 overexpression in IgG4-positive sialadenitis and IgG4-RD remains unknown.

Materials and methods

Here, we investigated toll-like receptor (TLR) - mediated bacterial inflammation in submandibular gland tissues of patients with IgG4-positive and IgG4-negative chronic inflammatory lesions of the submandibular gland (n = 61), with noninflamed submandibular glands serving as controls (n = 4). Utilising immunohistochemistry, we assessed the expression of TLR2 and TLR4, lipopolysaccharide (LPS) and the P. gingivalis-specific antigen gingipain R1.

Results

We observed TLR2- and TLR4-immunopositivity in 64 (98%) samples. However, TLR2 and TLR4 staining intensity was significantly stronger in the IgG4-positive group. LPS- and gingipain R1 immunopositivity were observed in 56 (86%) and 58 (89%) samples, respectively. LPS-positivity localised exclusively in mast cell-like cells, while gingipain R1-positivity remained scarce.

Conclusions

A stronger TLR2 or TLR4 expression in IgG4-positive sialadenitis may indicate a tissue-related factor underlying this form of chronic sialadenitis. LPS- and P. gingivalis immunopositivity remained weak throughout this series. Thus, gram-negative bacteria may not represent pathogens underlying these forms of chronic sialadenitis.

Case report and review of literature: IgG4-gastroduodenitis in upper GI Crohn's disease: two separate entities or just a marker of disease severity?

A 20-year-old man was presented with ulcerative gastritis and duodenitis complicated by pyloric stenosis. Helicobacter pylori infection was excluded, and the lesions did not respond to treatment with proton pump inhibitors. No other parts of the intestinal tract showed signs of inflammation. Histopathological review showed signs of chronic inflammation with granuloma formation. A tentative diagnosis of isolated upper gastrointestinal (UGI) Crohn's disease was performed. However, additional work-up revealed significantly positive IgG4 staining as well as elevated IgG4 serum levels. Since granulomatous disease is unlikely in IgG4-related disease, an eventual diagnosis of overlapping IgG4-related disease and Crohn's disease (CD) was performed. Treatment with systemic steroids and anti-TNF in combination with azathioprine led to rapid symptomatic improvement. In this article, we review the available literature on IgG4-related gastroduodenitis, granulomatous gastritis, and upper GI CD. We suggest the possibility that IgG4-infiltration may be a marker of severely active inflammatory bowel disease rather than a separate disease entity.

Coronary periarteritis and pericarditis are rare but distinct manifestations of heart involvement in IgG4-related disease: a retrospective cohort study

BACKGROUND

The heart can be involved in immunoglobulin (Ig)-G4-related disease (IgG4-RD). This study aimed to summarize the clinical features and efficacy of treatment for IgG4-RD patients with heart involvement.

METHODS

We conducted a retrospective study enrolling 42 IgG4-RD patients with heart involvement from the IgG4-RD cohorts of the Peking Union Medical College Hospital and Beijing An Zhen Hospital, from 2010 to 2022. Clinical, laboratory, radiological data were collected, and treatment responses to glucocorticoids and immunosuppressants were analyzed.

RESULTS

IgG4-related cardiac involvement is a rare part of the IgG4-RD spectrum. The incidences of coronary periarteritis and pericarditis were 1.2%(13/1075) and 3.1%(33/1075), respectively in our cohort. Valvular disease possibly related to IgG4-RD was detected in two patients. None of the patients with myocardial involvement were identified. The average age was 58.2 ± 12.8 years, with a male predominance (76.7%). Coronary artery CT revealed that mass-like and diffuse wall-thickening lesions were the most frequently observed type of coronary periarteritis. Pericarditis presented as pericardial effusion, localized thickening, calcification and mass. After treatment with glucocorticoid and immunosuppressants, all patients achieved a reduced IgG4-RD responder index score and achieved radiological remission. Two patients with coronary peri-arteritis experienced clinical relapses during the maintenance period.

CONCLUSIONS

Cardiac involvement in IgG4-RD is rare and easily overlooked since many patients are asymptomatic, and the diagnosis relies on imaging. Patients showed a satisfactory response to glucocorticoid based treatment.

IgG4-related disease complicated with diffuse and chronic gastrointestinal inflammation leading to small intestinal perforation

Immunoglobulin (Ig) G4-related disease (IgG4-RD) is a systemic inflammatory disease characterised by elevated serum IgG4, IgG4+ cell infiltration, storiform fibrosis, and obliterative phlebitis. While IgG4-RD can affect various organs, gastrointestinal tract involvement is less common. Here, we report a 70-year-old female with IgG4-RD complicated with diffuse and chronic gastrointestinal inflammation, which led to small intestinal perforation. She had been suffering from anorexia, abdominal pain, vomiting, and diarrhoea and hospitalised due to recurrent ileus. Consequently, she was referred due to small intestinal perforation required for surgical intervention. Pathology revealed acute and chronic inflammation with massive IgG4+ plasmacyte infiltration into mucosa of the small intestine and ischaemic change secondarily caused by chronic inflammation. Random biopsies from the mucosa of stomach, duodenum, ileum, and colon also revealed diffuse and massive IgG4+ plasmacyte infiltration in stomach, duodenum, small intestine, and colon. She was diagnosed with IgG4-RD based on the pathological findings and elevated serum IgG4 levels. Glucocorticoid rapidly ameliorated the symptoms. IgG4-RD may cause gastrointestinal manifestations, and histopathological assessment should be considered, even in the absence of specific characteristics of IgG4-RD.

Fibrotic phenotype of IgG4-related disease

A prompt response to glucocorticoids is a clinical hallmark of IgG4-related disease. However, manifestations characterised by prominent tissue fibrosis on histological examination can be less responsive to glucocorticoid therapy than other types of IgG4-related disease. These manifestations include retroperitoneal fibrosis, fibrosing mediastinitis, Riedel thyroiditis, orbital pseudotumor, and hypertrophic pachymeningitis, among others. To explain this discrepancy, a preliminary distinction into proliferative and fibrotic phenotypes of IgG4-related disease has been proposed on the basis of clinical presentation, pathological features, and response to immunosuppressive therapy. Implications of this classification for patient management remain an important area of investigation. In this Series paper, we aim to dissect the pathophysiology of tissue fibrosis in IgG4-related disease and discuss how clinicians should approach the management of fibrotic manifestations of IgG4-related disease based on the most recent diagnostic and therapeutic developments.

Is systemic lupus erythematosus linked to Immunoglobulin G4 Autoantibodies?

Systemic lupus erythematosus (SLE) is a systemic autoimmune disorder characterized by a hyperactive immune system with multiple abnormalities in B-cell proliferation, antibody production, T-cell regulation, and immune complex (IC) formation. In humans, Immunoglobulin (Ig) G is found in four subclasses. IgG1-IgG4, which are distinguished by both structural and biological differences. Fab-arm Exchange (FAE), specific biases in the IgG4 response repertoire, and a decreased capacity to induce effector functions mediated by interactions in the fragment crystallizable (Fc) region are just a few of the distinctive characteristics of IgG4. The recent finding of the presence of double-stranded DNA (dsDNA) and antinuclear antibody (ANA)-IgG4 has raised attention to this IgG subclass and its possible role in SLE. IgG4 was previously believed to just have anti-inflammatory effects by inhibiting immune responses, but recent studies have shown that these antibodies can also play a role in the onset and development of some clinical disorders. To consider the clinical effects of IgG4 presence, it is necessary to discuss its characteristics, which could underlie the potential role it can play in SLE. Therefore, this study aimed to comprehensively review the role of IgG4 in SLE to elucidate the collective incidence of high IgG4 levels reported in some SLE patients.

Lateral micro-orbitotomy as the technique of choice for orbital pseudotumor in IgG4-RD. Case report and review of the literature

Immunoglobulin G4-related disease (IgG4-RD) is characterized by a systemic fibroinflammatory infiltrate that often involves the orbit in addition to other tissues. Thus it has to be considered in the differential diagnosis of orbital tumors. We report the clinical case of a 64-year-old woman who presented with right mydriasis, progressive proptosis and paralysis of the third cranial nerve of 1 year of evolution. Cranial MRI identified an intraconal lesion of the right orbit, located between the external and inferior rectus muscles and the optic nerve, and she was scheduled for surgery by transcranial approach with lateral micro-orbitomy. A satisfactory macroscopic excision was achieved with no remarkable complications and a definitive deferred histological result of pseudotumor by IgG4-RD. Follow-up for 24 months showed no tumor recurrence, and the patient clinically improved from ophthalmoplegia. This case highlights the efficacy of lateral orbitotomy in the etiologic diagnosis and successful therapeutic outcome of complex orbital lesions associated with IgG4-RD pseudotumor.

18 F-FDG PET/CT in Pediatric Immunoglobulin G4-Related Disease

ABSTRACT

A 14-year-old boy presented with severe, nonintentional weight loss, fatigue, and cough. Investigations were notable for raised inflammatory markers and significantly elevated serum immunoglobulin G4 (IgG4). 18 F-FDG PET/CT was obtained for assessment of disease involvement and extent, to exclude differential diagnoses and to guide biopsy. The study demonstrated extensive FDG-avid nodal disease and multisystem organ involvement. Excisional biopsy of a right inguinal lymph node demonstrated reactive changes with numerous IgG4-positive plasma cells consistent with IgG4-related disease. He was commenced on immunosuppressive therapy with consequent weight restoration and symptom resolution.

IgG4-related disease with nasopharyngeal malignancy-like manifestations

Background

IgG4-related disease (IgG4-RD) was characterized by single or multiple masses in organs, which may mimic various inflammatory and malignant diseases. Here, we summarize 4 patients with aggressive manifestations of IgG4-RD that mimic nasopharynx cancer to provide some new sights for the diagnosis of IgG4-RD.

Case summary

Four patients were included in our series. The age ranged from 53 to 64 years old, and the duration of the disease ranged from 4 to 6 months. The chief complaints included headache, rhinorrhea, or diplopia. All patients had more than 10 IgG4+ plasma cells/HPF in immunohistochemistry with plasma lgG4 levels ranging from 218 mg/dL to 765 mg/dL. All of them met the diagnostic criteria of lgG4-RD.

Conclusion

The described case is highly similar to the clinical manifestations of nasopharyngeal carcinoma. Although pathology is the gold standard, there are still limitations. Serological IgG4 can help confirm the diagnosis. Timely diagnosis of IgG4-RD is of great significance in preventing secondary organ damage in patients with active diseases.

Pathogenic roles of follicular helper T cells in IgG4-related disease and implications for potential therapy

IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems. Recent advancements have significantly enhanced our understanding of the pathological mechanism underlying this immune-mediated disease. T cell immunity plays a crucial role in the pathogenesis of IgG4-RD, and follicular helper T cells (Tfh) are particularly important in germinal center (GC) formation, plasmablast differentiation, and IgG4 class-switching. Apart from serum IgG4 concentrations, the expansion of circulating Tfh2 cells and plasmablasts may also serve as novel biomarkers for disease diagnosis and activity monitoring in IgG4-RD. Further exploration into the pathogenic roles of Tfh in IgG4-RD could potentially lead to identifying new therapeutic targets that offer more effective alternatives for treating this condition. In this review, we will focus on the current knowledge regarding the pathogenic roles Tfh cells play in IgG4-RD and outline potential therapeutic targets for future clinical intervention.

The "great imitator": IgG4-related disease of the oral cavity. Two case reports and scoping review

This study aimed to review the lesser-known intraoral manifestations of immunoglobulin G4-related disease (IgG4-RD). In this paper we report an unprecedented case of oral IgG4-RD mimicking angiolymphoid hyperplasia with eosinophilia (ALHE), and another case presenting as plasma cell gingivitis. We then performed a scoping review of published cases of IgG4-RD involving the oral cavity. The following data were collected for each case: age, sex, intraoral site(s) involved, clinical appearance, imaging features, serum IgG4 values, histopathology, treatment, and follow-up duration. Fifty-one cases of oral IgG4-RD were published in literature. The hard palate and jaw bones were the two main locations reported, while the histological identification of a IgG4/IgG plasma cells ratio ≥40% was fundamental for diagnosis. Conversely, the pathological features of storiform fibrosis and obliterative phlebitis were not common. Future reports regarding oral IgG4-RD should report clear adherence to the recognized international diagnostic criteria of the disease.

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.

Single-Cell Sequencing: High-Resolution Analysis of Cellular Heterogeneity in Autoimmune Diseases

Autoimmune diseases (AIDs) are complex in etiology and diverse in classification but clinically show similar symptoms such as joint pain and skin problems. As a result, the diagnosis is challenging, and usually, only broad treatments can be available. Consequently, the clinical responses in patients with different types of AIDs are unsatisfactory. Therefore, it is necessary to conduct more research to figure out the pathogenesis and therapeutic targets of AIDs. This requires research technologies with strong extraction and prediction capabilities. Single-cell sequencing technology analyses the genomic, epigenomic, or transcriptomic information at the single-cell level. It can define different cell types and states in greater detail, further revealing the molecular mechanisms that drive disease progression. These advantages enable cell biology research to achieve an unprecedented resolution and scale, bringing a whole new vision to life science research. In recent years, single-cell technology especially single-cell RNA sequencing (scRNA-seq) has been widely used in various disease research. In this paper, we present the innovations and applications of single-cell sequencing in the medical field and focus on the application contributing to the differential diagnosis and precise treatment of AIDs. Despite some limitations, single-cell sequencing has a wide range of applications in AIDs. We finally present a prospect for the development of single-cell sequencing. These ideas may provide some inspiration for subsequent research.

Immunoglobulin G4-related disease mimicking an appendiceal neoplasm: a case report

Immunoglobulin G4-related disease (IgG4-RD) is a fibroinflammatory condition characterized by chronic activation of the immune system and a tendency to form tumorous lesions. IgG4-RD is frequently characterized by the presence of tumor-like masses affecting multiple organs and is easily mistaken for a malignant neoplasm. However, IgG4-RD affecting the appendix is extremely rare, with only seven cases reported previously. We report the case of a woman in her early 60s who presented with insidious abdominal pain and radiological findings mimicking appendiceal neoplasms. After diagnosing appendiceal neoplasms, surgery was performed. The patient had a serum IgG4 concentration of <1.35 g/L, which did not satisfy one of the three revised comprehensive diagnostic criteria for IgG4-RD. A pathological examination was conducted, and the patient was diagnosed with appendiceal IgG4-RD. To the best of our knowledge, there have been no previously reported cases of IgG4-RD affecting the appendix in patients with low serum IgG4 concentrations. This report may prove beneficial for the future understanding of IgG4-RD and for the revision of diagnostic and treatment strategies.

Chronic Sclerosing Sialadenitis of the Submandibular Gland and its Histopathological Spectrum in the IgG4-Related Disease: a Series of 17 Cases

PURPOSE

This study aimed to characterize the histopathological immunohistochemical features of chronic sclerosing sialadenitis, emphasizing the IgG4-related disease.

METHODS

Seventeen cases of chronic sclerosing sialoadenitis were examined for histopathological aspects, (inflammation, fibrosis, glandular parenchyma, and lymphoid follicles) and immunohistochemistry (BCL2, CD3, CD20, CD34, CD163, p63, cyclin D1, mast cell, SMA, S100A4, IgG, and IgG4) which were scored. IgG4-related disease features were investigated. Demographic and clinical data were also collected.

RESULTS

Males predominated (10:7), with an average lesion size of 3.9 cm. Common histopathological findings included reduced acinar parenchyma, lymphoid follicle formation, and ductular proliferation. CD3-positive T lymphocytes and CD34- and SMA-positive stromal fibroblasts were abundant. Nine cases (53%) showed sialoliths and three cases met the criteria for IgG4-related disease.

CONCLUSION

CSS of the submandibular gland represents a reactive pattern rather than IgG4-RD as only 3 cases seemed to be related to IgG4-RD. The immunohistochemical profile revealed an abundant population of CD3-positive T lymphocytes, as opposed to regulatory proteins such as cyclin D1, demonstrating that populations of CD34- and SMA-positive stromal fibroblasts contribute to the fibrosis characteristic of CSS. In addition, our results provide a comprehensive insight into the study of CSS and its relationship with IgG4-RD.

Immunoglobulin G4-related sclerosing mastitis: an unexpected diagnosis for a breast mass

Immunoglobulin G4-related disease is an immune-mediated condition comprised of a number of various disorders sharing unique pathologic, serologic, and clinical features. Diagnosis of immunoglobulin G4-related sclerosing mastitis is challenging as the clinical and imaging findings mimic breast malignancies or other types of inflammatory mastitis. Herein, we describe a case of a female patient with a painless palpable mass in her right breast. An excisional core biopsy led to the rare diagnosis of immunoglobulin G4-related sclerosing mastitis, and the patient received steroid treatment for a month. To date, the patient has remained disease-free without any recurrence. As immunoglobulin G4-related sclerosing mastitis is a very rare disease, further studies are needed to reach conclusions about the pathogenesis, diagnosis, and treatment of this entity.

Exploring the depths of IgG4: insights into autoimmunity and novel treatments

IgG4 subclass antibodies represent the rarest subclass of IgG antibodies, comprising only 3-5% of antibodies circulating in the bloodstream. These antibodies possess unique structural features, notably their ability to undergo a process known as fragment-antigen binding (Fab)-arm exchange, wherein they exchange half-molecules with other IgG4 antibodies. Functionally, IgG4 antibodies primarily block and exert immunomodulatory effects, particularly in the context of IgE isotype-mediated hypersensitivity reactions. In the context of disease, IgG4 antibodies are prominently observed in various autoimmune diseases combined under the term IgG4 autoimmune diseases (IgG4-AID). These diseases include myasthenia gravis (MG) with autoantibodies against muscle-specific tyrosine kinase (MuSK), nodo-paranodopathies with autoantibodies against paranodal and nodal proteins, pemphigus vulgaris and foliaceus with antibodies against desmoglein and encephalitis with antibodies against LGI1/CASPR2. Additionally, IgG4 antibodies are a prominent feature in the rare entity of IgG4 related disease (IgG4-RD). Intriguingly, both IgG4-AID and IgG4-RD demonstrate a remarkable responsiveness to anti-CD20-mediated B cell depletion therapy (BCDT), suggesting shared underlying immunopathologies. This review aims to provide a comprehensive exploration of B cells, antibody subclasses, and their general properties before examining the distinctive characteristics of IgG4 subclass antibodies in the context of health, IgG4-AID and IgG4-RD. Furthermore, we will examine potential therapeutic strategies for these conditions, with a special focus on leveraging insights gained from anti-CD20-mediated BCDT. Through this analysis, we aim to enhance our understanding of the pathogenesis of IgG4-mediated diseases and identify promising possibilities for targeted therapeutic intervention.

Multi-Modality Imaging in Vasculitis

Systemic vasculitides are a rare and complex group of diseases that can affect multiple organ systems. Clinically, presentation may be vague and non-specific and as such, diagnosis and subsequent management are challenging. These entities are typically classified by the size of vessel involved, including large-vessel vasculitis (giant cell arteritis, Takayasu's arteritis, and clinically isolated aortitis), medium-vessel vasculitis (including polyarteritis nodosa and Kawasaki disease), and small-vessel vasculitis (granulomatosis with polyangiitis and eosinophilic granulomatosis with polyangiitis). There are also other systemic vasculitides that do not fit in to these categories, such as Behcet's disease, Cogan syndrome, and IgG4-related disease. Advances in medical imaging modalities have revolutionized the approach to diagnosis of these diseases. Specifically, color Doppler ultrasound, computed tomography and angiography, magnetic resonance imaging, positron emission tomography, or invasive catheterization as indicated have become fundamental in the work up of any patient with suspected systemic or localized vasculitis. This review presents the key diagnostic imaging modalities and their clinical utility in the evaluation of systemic vasculitis.

Current and future advances in practice: IgG4-related disease

IgG4-related disease (IgG4-RD) is an increasingly recognized cause of fibroinflammatory lesions in patients of diverse racial and ethnic backgrounds and is associated with an increased risk of death. The aetiology of IgG4-RD is incompletely understood, but evidence to date suggests that B and T cells are important players in pathogenesis, both of which are key targets of ongoing drug development programmes. The diagnosis of IgG4-RD requires clinicopathological correlation because there is no highly specific or sensitive test. Glucocorticoids are highly effective, but their use is limited by toxicity, highlighting the need for studies investigating the efficacy of glucocorticoid-sparing agents. B cell-targeted therapies, particularly rituximab, have demonstrated benefit, but no randomized clinical trials have evaluated their efficacy. If untreated or under-treated, IgG4-RD can cause irreversible organ damage, hence close monitoring and consideration for long-term immunosuppression is warranted in certain cases.

New insights into chronic rhinosinusitis associated with IgG4-related disease

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

Cardiovascular pathology in vasculitis

Vasculitides are diseases that can affect any vessel. When cardiac or aortic involvement is present, the prognosis can worsen significantly. Pathological assessment often plays a key role in reaching a definite diagnosis of cardiac or aortic vasculitis, particularly when the clinical evidence of a systemic inflammatory disease is missing. The following review will focus on the main histopathological findings of cardiac and aortic vasculitides.

Granzyme K- and amphiregulin-expressing cytotoxic T cells and activated extrafollicular B cells are potential drivers of IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD), an example of a type I immune disease, is an immune-mediated fibrotic disorder characterized by dysregulated resolution of severe inflammation and wound healing. However, truly dominant or pathognomonic autoantibodies related to IgG4-RD are not identified.

OBJECTIVE

We sought to perform single-cell RNA sequencing and T-cell receptor and B-cell receptor sequencing to obtain a comprehensive, unbiased view of tissue-infiltrating T and B cells.

METHODS

We performed unbiased single-cell RNA-sequencing analysis for the transcriptome and T-cell receptor sequencing and B-cell receptor sequencing on sorted CD3+ T or CD19+ B cells from affected tissues of patients with IgG4-RD. We also conducted quantitative analyses of CD3+ T-cell and CD19+ B-cell subsets in 68 patients with IgG4-RD and 30 patients with Sjögren syndrome.

RESULTS

Almost all clonally expanded T cells in these lesions were either Granzyme K (GZMK)-expressing CD4+ cytotoxic T cells or GZMK+CD8+ T cells. These GZMK-expressing cytotoxic T cells also expressed amphiregulin and TGF-β but did not express immune checkpoints, and the tissue-infiltrating CD8+ T cells were phenotypically heterogeneous. MKI67+ B cells and IgD-CD27-CD11c-CXCR5- double-negative 3 B cells were clonally expanded and infiltrated affected tissue lesions. GZMK+CD4+ cytotoxic T cells colocalized with MKI67+ B cells in the extrafollicular area from affected tissue sites.

CONCLUSIONS

The above-mentioned cells likely participate in T-B collaborative events, suggesting possible avenues for targeted therapies. Our findings were validated using orthogonal approaches, including multicolor immunofluorescence and the use of comparator disease groups, to support the central role of cytotoxic CD4+ and CD8+ T cells expressing GZMK, amphiregulin, and TGF-β in the pathogenesis of inflammatory fibrotic disorders.

Validation of the Diagnostic Criteria for IgG4-Related Periaortitis/Periarteritis and Retroperitoneal Fibrosis (IgG4PA/RPF) 2018, and Proposal of a Revised 2023 Version for IgG4-Related Cardiovascular/Retroperitoneal Disease

BACKGROUND

In 2018, diagnostic criteria were introduced for IgG4-related periaortitis/periarteritis and retroperitoneal fibrosis (PA/RPF). This study assessed the existing criteria and formulated an improved version.Methods and Results: Between August 2022 and January 2023, we retrospectively analyzed 110 Japanese patients diagnosed with IgG4-related disease (IgG4-RD) involving cardiovascular and/or retroperitoneal manifestations, along with 73 non-IgG4-RD patients ("mimickers") identified by experts. Patients were stratified into derivation (n=88) and validation (n=95) groups. Classification as IgG4-RD or non-IgG4-RD was based on the 2018 diagnostic criteria and various revised versions. Sensitivity and specificity were calculated using experts' diagnosis as the gold standard for the diagnosis of true IgG4-RD and mimickers. In the derivation group, the 2018 criteria showed 58.5% sensitivity and 100% specificity. The revised version, incorporating "radiologic findings of pericarditis", "eosinophilic infiltration or lymphoid follicles", and "probable diagnosis of extra-PA/-RPF lesions", improved sensitivity to 69.8% while maintaining 100% specificity. In the validation group, the original and revised criteria had sensitivities of 68.4% and 77.2%, respectively, and specificities of 97.4% and 94.7%, respectively.

CONCLUSIONS

Proposed 2023 revised IgG4-related cardiovascular/retroperitoneal disease criteria show significantly enhanced sensitivity while preserving high specificity, achieved through the inclusion of new items in radiologic, pathological, and extra-cardiovascular/retroperitoneal organ categories.

The development and initial validation of IgG4-related disease damage index: a consensus report from Chinese IgG4-RD Consortium

OBJECTIVE

To develop and conduct an initial validation of the Damage Index for IgG4-related disease (IgG4-RD DI).

METHODS

A draft of index items for assessing organ damages in patients with IgG4-RD was generated by experts from the Chinese IgG4-RD Consortium (CIC). The preliminary DI was refined using the Delphi method, and a final version was generated by consensus. 40 IgG4-RD cases representing four types of clinical scenarios were then selected, each with two time points of assessment for at least 3 years of follow-up. 48 rheumatologists from 35 hospitals nationwide were invited to evaluate organ damage using the CIC IgG4-RD DI. The intraclass correlation coefficient (ICC) and the Kendall-W coefficient of concordance (KW) were used to assess the inter-rater reliability. The criterion validity of IgG4-RD DI was tested by calculating the sensitivity and specificity of raters.

RESULTS

IgG4-RD DI is a cumulative index consisting of 14 domains of organ systems, including a total of 39 items. The IgG4-RD DI was capable of distinguishing stable and increased damage across the active disease subgroup and stable disease subgroup. In terms of scores at baseline and later observations by all raters, overall consistency in scores at baseline and later observations by all raters was satisfactory. ICC at the two time points was 0.69 and 0.70, and the KW was 0.74 and 0.73, respectively. In subgroup analysis, ICC and KW in all subgroups were over 0.55 and 0.61, respectively. The analysis of criterion validity showed a good performance with a sensitivity of 0.86 (95% CI 0.82 to 0.88), a specificity of 0.79 (95% CI 0.76 to 0.82) and an area under the curve of 0.88 (95% CI 0.85 to 0.91).

CONCLUSION

The IgG4-RD DI is a useful approach to analyse disease outcomes, and it has good operability and credibility. It is anticipated that the DI will become a useful tool for therapeutic trials and studies of prognosis in patients with IgG4-RD.

IgG4-related disease: an update on pathology and diagnostic criteria with a focus on salivary gland manifestations

Immunoglobulin G4-related disease (IgG4-RD) is a multi-organ disorder characterized by a highly variable clinical presentation depending on the affected organ/s, extent of tumefactive fibroinflammatory lesions, and associated functional impairment. The disease pursues a chronic, relapsing, often asymptomatic course and hence may pose a significant diagnostic challenge. Diagnostic delay can lead to progressive fibrosis and irreversible organ damage resulting into significant morbidity and even mortality. Given its broad clinical spectrum, physicians of all specialties may be the first clinicians facing this diagnostic challenge. Outside the pancreatobiliary system, the head and neck represents the major site of IgG4-RD with variable organ-specific diffuse or mass-forming lesions. In up to 75% of cases, elevated serum IgG4 levels are observed, but this figure possibly underestimates the fraction of seronegative cases, as the disease manifestations may present metachronously with significant intervals. Together with negative serology, this can lead to misdiagnosis of seronegative cases. A standardized nomenclature and diagnostic criteria for IgG4-RD were established in 2012 and revised in 2020 facilitating scientific research and expanding the range of diseases associated with IgG4 abnormalities. In addition to orbital pseudotumor, dacryoadenitis, Riedel thyroiditis, sinonasal manifestations, and rare miscellaneous conditions, IgG4-related sialadenitis is one of the most frequent presentations in the head and neck region. However, controversy still exists regarding the relationship between sialadenitis and IgG4-RD. This review focuses on the clinicopathological features of IgG4-related sialadenitis and its contemporary diagnostic criteria.

Mimickers of immunoglobulin G4-related hepatobiliary disease on biopsy

With the growing recognition of IgG4-related hepatobiliary disease, establishing a definitive diagnosis relies mainly on a combination of clinical findings, serological markers, and imaging modalities. However, the role of histopathological evaluation remains indispensable, particularly in cases necessitating differential diagnosis or malignancy exclusion. While diagnosing IgG4-related hepatobiliary disease through surgical resection specimens is often straightforward, pathologists encounter substantial challenges when evaluating biopsies. The increasing rarity of surgical interventions exacerbates this due to improved disease recognition and suspicion. Numerous confounding factors, including the absence of the characteristic histologic features, limited tissue sample size, biopsy artifacts, and the limited value of IgG4 counts, further complicate the diagnostic process. Additionally, many other disorders exhibit clinical and histological features that overlap with IgG4-related disease, intensifying the complexity of interpreting biopsy specimens. This article explores the clinical and histomorphologic features of IgG4-related hepatobiliary disease and its potential mimickers. It offers valuable insights for pathologists and clinicians when confronted with biopsy specimens from hepatobiliary organs.

IgG4-related kidney disease: Clinicopathologic features, differential diagnosis, and mimics

IgG4-related kidney disease (IgG4-RKD) encompasses all forms of kidney disease that are part of IgG4-related disease (IgG4-RD). First recognized as IgG4-related tubulointerstitial nephritis (IgG4-TIN), and then IgG4-related membranous glomerulonephritis (IgG4-MGN), we now recognize additional patterns of interstitial nephritis, glomerular disease, and vascular disease that can be seen as part of IgG4-RKD. The clinical presentation is variable and can include acute or chronic kidney injury, proteinuria or nephrotic syndrome, mass lesion(s), and obstruction. While usually associated with other organ involvement by IgG4-RD, kidney-alone involvement is present in approximately 20 % of IgG4-RKD. Compared to IgG4-RD overall, patients with IgG4-RKD are more likely to show increased serum IgG4 or IgG, and more likely to have hypocomplementemia. In this review, we extensively cover other types of autoimmune and plasma cell-rich interstitial nephritis, mass forming inflammatory diseases of the kidney, and other mimics of IgG4-TIN, in particular ANCA-associated disease.

Performance of the 2019 ACR/EULAR Classification Criteria for IgG4-Related Disease in a Large Chinese Cohort

OBJECTIVE

The purpose of this research was to ascertain the effectiveness of the newly established criteria for classifying IgG4-related disease (IgG4-RD), as applied to a large Chinese cohort in real-world clinical settings.

METHODS

Patient data were procured from the digital health records of 4 prominent academic hospitals. The criterion standard for identifying IgG4-RD patients was from a seasoned rheumatologist. The control group consisted of individuals with other ailments such as cancer, other forms of pancreatitis, infectious diseases, and illnesses that mimic IgG4-RD.

RESULTS

A total of 605 IgG4-RD patients and 760 mimickers were available for analysis. The 2019 EULAR/ACR criteria have a sensitivity of 69.1% and a specificity of 90.9% in this large Chinese cohort. IgG4-RD had a greater proportion of males (55.89% vs 36.25%, p < 0.001), an older average age at diagnosis (54.91 ± 13.44 vs 48.91 ± 15.71, p < 0.001), more pancreatic (29.59% vs 6.12%, p < 0.001) and salivary gland (63.30% vs 27.50%, p < 0.001) involvement, and a larger number of organ involvement (3.431 ± 2.054 vs 2.062 ± 1.748, p < 0.001) compared with mimickers.

CONCLUSIONS

The 2019 EULAR/ACR criteria are effective in classifying IgG4-RD in Chinese patients, demonstrating high specificity and moderate sensitivity.

An overlapping case of IgG4-related disease and systemic lupus erythematosus treated with belimumab: a case-based review

IgG4-related disease (IgG4-RD) is a systemic condition in which IgG4+ plasma cell infiltration and fibrosis cause organ swelling and lead to diverse clinical manifestations. Although IgG4-RD typically responds to glucocorticoids (GCs), relapse during tapering occurs and an early GC-sparing approach might therefore be beneficial. Systemic lupus erythematosus (SLE) is a chronic inflammatory disease with multiple symptoms that is also treated with GCs as a first-line therapy. Recently, belimumab, a recombinant human IgG-1λ monoclonal antibody that inhibits B-cell activating factor, was approved, but reports of use for IgG4-RD are scarce. Here, we present a rare case of IgG4-RD complicated with SLE which was successfully treated with belimumab. A 67-year-old man was diagnosed with IgG4-RD based on a high serum IgG4 level and histopathological findings. Furthermore, he had pericardial effusion on echocardiography, and laboratory tests revealed thrombocytopenia, autoimmune hemolysis, positive anti-nuclear antibodies, positive anti-DNA antibodies, and hypocomplementemia. These data led to an SLE diagnosis. Treatment was started with prednisolone at 40 mg/day, plus hydroxychloroquine, which initially improved both the SLE and IgG4-RD symptoms. During the GC tapering, belimumab was added and clinical symptoms resolved completely. Our case and the literature review summarize reported rare overlapping cases of IgG4-RD and SLE and suggest that belimumab is a promising candidate for the treatment of IgG4-RD.

PLA2R-positive membranous nephropathy in IgG4-related disease

BACKGROUND

IgG4-related disease (IgG4-RD) is a fibroinflammatory disease that affects multiple organs, including the pancreas, lacrimal glands, salivary glands, periaortic/retroperitoneum, and kidney. Interstitial nephritis is a typical renal disorder associated with IgG4-RD, but membranous nephropathy is also seen in some cases.

CASE PRESENTATION

Herein we report on the case of a 77-year-old male patient with nephrotic syndrome and IgG4-related lung disease. His serum phospholipase A2 receptor (PLA2R) antibody was positive. His renal biopsy specimen was also positive for PLA2R. The renal biopsy specimen showed membranous nephropathy with equal IgG3 and IgG4 immunofluorescence staining and no interstitial nephritis, suggesting IgG4-RD manifesting as membranous nephropathy.

CONCLUSIONS

Nephrotic syndrome caused by membranous nephropathy is sometimes associated with IgG4-RD. In such cases, even if serum PLA2R antibody is positive, it should be considered that the membranous nephropathy may be secondary to IgG4-RD.

A Case of Castleman's Disease with a Marked Infiltration of IgG4-Positive Cells in the Renal Interstitium

Multicentric Castleman's disease (MCD) is a benign lymphoproliferative disorder with heterogenous clinical symptoms, and involves systemic organs in addition to lymph nodes. Herein, we present the case of a 55-year-old man with MCD characterized by an extensive infiltration of IgG4+ plasma cells in the kidneys. The patient presented to our hospital with a high fever and diarrhea. On admission, laboratory analysis revealed anemia, renal dysfunction (eGFR 30 mL/min/1.73 m2), polyclonal gammopathy (IgG 7130 mg/dL), elevated serum IgG4 level (2130 mg/dL), and increased C-reactive protein (8.0 mg/dL). An enlargement of lymph nodes in the axillary, mediastinal, para-aortic, and inguinal regions was observed on abdominal computed tomography. Axillary lymph node biopsy revealed interfollicular expansion due to dense plasma cell infiltration. Renal biopsy demonstrated significant plasma cell infiltration into the tubulointerstitium. Immunohistochemical analysis showed a 40% IgG4-positive/IgG-positive plasma cell ratio, meeting the diagnostic criteria for an IgG4-related disease. Amyloid A deposition was observed along vessel walls, and immunofluorescence analysis indicated granular positivity of IgG and C3 along the glomerular capillary wall. Elevated levels of interleukin-6 (21 pg/mL) and vascular endothelial growth factor (VEGF; 1210 pg/mL) were noted. Based on these findings, and the histological finding of the lymph node biopsy, idiopathic MCD was diagnosed. Corticosteroid monotherapy was only partially effective. Subsequently, tocilizumab administration was initiated, leading to sustained remission, even after discontinuation of prednisolone. Due to the diverse responses to steroid therapy and the varying prognoses observed in MCD and IgG4-related disease, it is essential to carefully diagnose MCD by thoroughly assessing the organ distribution of the disease, its response to steroid therapy, and any additional pathological findings.

Pathogenesis of Warthin's Tumor: Neoplastic or Non-Neoplastic?

Warthin's tumor is the second most frequent neoplasm next to pleomorphic adenoma in the salivary gland, mostly in the parotid gland. The epithelial cells constituting a tumor are characterized by the presence of mitochondria that undergo structural and functional changes, resulting in the development of oncocytes. In addition to containing epithelial cells, Warthin's tumors contain abundant lymphocytes with lymph follicles (germinal centers) that are surrounded by epithelial cells. The pathogenesis of Warthin's tumor is not fully understood, and several hypotheses have been proposed. The risk factors for the development of Warthin's tumor, which predominantly occurs in males, include aging, smoking, and radiation exposure. Recently, it has been reported that chronic inflammation and aging cells promote the growth of Warthin's tumor. Several reports regarding the origin of the tumor have suggested that (1) Warthin's tumor is an IgG4-related disease, (2) epithelial cells that compose Warthin's tumor accumulate mitochondria, and (3) Warthin's tumor is a metaplastic lesion in the lymph nodes. It is possible that the pathogenesis of Warthin's tumor includes mitochondrial metabolic abnormalities, accumulation of aged cells, chronic inflammation, and senescence-associated secretory phenotype (SASP). In this short review, we propose that DNA damage, metabolic dysfunction of mitochondria, senescent cells, SASP, human papillomavirus, and IgG4 may be involved in the development of Warthin's tumor.

A case of IgG4-related ophthalmic disease after SARS-CoV-2 vaccination: case report and literature review

Coronavirus disease 19 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is affecting the world with a surge in cases. A variety of autoimmune diseases occur after SARS-CoV-2 infection or vaccination, of which IgG4-related disease (IgG4-RD) is an important type. IgG4-RD can involve multiple organs of the body. The ocular manifestation of IgG4-RD is called IgG4-related ophthalmic disease (IgG4-ROD). We herein report a patient diagnosed with IgG4-ROD. The patient developed ptosis and vision loss after SARS-CoV-2 vaccination, and the symptoms worsened after SARS-CoV-2 infection. After excluding other diseases like myasthenia gravis and Eaton-Lambert syndrome that may cause ptosis, the diagnosis of IgG4-ROD was confirmed by pathological examination. We discussed the predisposing factors, diagnosis and treatment of this patient to provide a more empirical and theoretical basis for clinical diagnosis and treatment. We conducted a literature review of previously reported cases of IgG4-RD following SARS-CoV-2 infection or vaccination. We retrieved a total of 9 cases, of which 5 developed symptoms after vaccination and 4 after infection. Demographic and clinical characteristics were summarized. In conclusion, our case represents the first case of proven IgG4-ROD after COVID-19 vaccination. We believe that IgG4-ROD and SARS-CoV-2 infection or vaccination are closely related, and the immune system disorder caused by SARS-CoV-2 infection or vaccination may be a key factor in the pathogenesis of IgG4-RD. But for now, there is no direct evidence that there is a causal relationship between SARS-CoV-2 infection or vaccination and IgG4-ROD, which still needs more research and exploration to confirm.

Comparison of clinical features and outcomes of proliferative, fibrotic, and mixed subtypes of IgG4-related disease: A retrospective cohort study

BACKGROUND

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized immune-mediated disorder that can affect almost any organ in the human body. IgG4-RD can be categorized into proliferative and fibrotic subtypes based on patients' clinicopathological characteristics. This study aimed to compare the clinical manifestations, laboratory findings, and treatment outcomes of IgG4-RD among different subtypes.

METHODS

We prospectively enrolled 622 patients with newly diagnosed IgG4-RD at Peking Union Medical College Hospital from March 2011 to August 2021. The patients were divided into three groups according to their clinicopathological characteristics: proliferative, fibrotic, and mixed subtypes. We compared demographic features, clinical manifestations, organ involvement, laboratory tests, and treatment agents across three subtypes. We then assessed the differences in treatment outcomes among 448 patients receiving glucocorticoids alone or in combination with immunosuppressants. Moreover, risk factors of relapse were revealed by applying the univariate and multivariate Cox regression analysis.

RESULTS

We classified the 622 patients into three groups consisting of 470 proliferative patients, 55 fibrotic patients, and 97 mixed patients, respectively. We found that gender distribution, age, disease duration, and frequency of allergy history were significantly different among subgroups. In terms of organ involvement, submandibular and lacrimal glands were frequently involved in the proliferative subtype, while retroperitoneum was the most commonly involved site in both fibrotic subtype and mixed subtype. The comparison of laboratory tests revealed that eosinophils ( P = 0.010), total IgE ( P = 0.006), high-sensitivity C-reactive protein ( P <0.001), erythrocyte sedimentation rate ( P <0.001), complement C4 ( P <0.001), IgG ( P = 0.001), IgG1 (P <0.001), IgG4 (P <0.001), and IgA ( P <0.001), at baseline were significantly different among three subtypes. Compared with proliferative and mixed subtypes, the fibrotic subtype showed the lowest rate of relapse (log-rank P = 0.014).

CONCLUSIONS

Our study revealed the differences in demographic characteristics, clinical manifestations, organ involvement, laboratory tests, treatment agents, and outcomes across proliferative, fibrotic, and mixed subtypes in the retrospective cohort study. Given significant differences in relapse-free survival among the three subtypes, treatment regimens, and follow-up frequency should be considered separately according to different subtypes.

18F-FAPI-04 Outperforms 18F-FDG PET/CT in Clinical Assessments of Patients with Pancreatic Adenocarcinoma

Accurate diagnosis and staging are crucial for selecting treatment for patients with pancreatic ductal adenocarcinoma (PDAC). The desmoplastic responses associated with PDAC are often characterized by hypometabolism. Here, we investigated 18F-fibroblast activation protein inhibitor (FAPI)-04 PET/CT in evaluation of PDAC and compared the findings with those obtained using 18F-FDG. Methods: Sixty-two PDAC patients underwent 18F-FAPI-04 PET/CT and 18F-FDG PET/CT. Identification of primary lesions, lymph node (LN) metastasis, and distant metastasis (DM) by these methods was evaluated, and TNM staging was performed. Correlation between SUVmax of the primary lesion and treatment response was explored in patients who received systemic therapy. Results: 18F-FAPI-04 PET/CT identified all patients with PDAC; 18F-FDG PET/CT missed 1 patient. Tracer uptake was higher in 18F-FAPI-04 PET/CT than in 18F-FDG PET/CT in primary tumors (10.63 vs. 2.87, P < 0.0001), LN metastasis (2.90 vs. 1.43, P < 0.0001), and DM (liver, 6.11 vs. 3.10, P = 0.002; peritoneal, 4.70 vs. 2.08, P = 0.015). The methods showed no significant difference in the T staging category, but the N and M values were significantly higher for 18F-FAPI-04 PET/CT than for 18F-FDG PET/CT (P = 0.002 and 0.008, respectively). Thus, 14 patients were upgraded, and only 1 patient was downgraded, by 18F-FAPI-04 PET/CT compared with 18F-FDG PET/CT. A high SUVmax of the primary tumor did not correlate with treatment response for either 18F-FAPI-04 or 18F-FDG. Conclusion: 18F-FAPI-04 PET/CT performed better than 18F-FDG PET/CT in identification of primary tumors, LN metastasis, and DM and in TNM staging of PDAC.