How to diagnose IgG4-related disease

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.

Cryo-transbronchial lung biopsy in the diagnosis of IgG4-related lung disease

IgG4-related lung disease is a diagnostic challenge as the presenting patterns can mimic other commonly seen pulmonary diseases like infections, interstitial pneumonia, malignancy, etc. The diagnosis of IgG4-related disease requires a correlation of clinical, radiological, biochemical, and histopathological features. Especially, an adequate tissue sample is necessary to diagnose this disease confidently. Conventionally surgical lung biopsy was needed for histopathology. But with the availability of the new less invasive technique-transbronchial cryo lung biopsy, adequate tissue can be obtained to clinch the diagnosis via bronchoscopy, thereby avoiding surgery. We report a case of IgG4-related interstitial lung disease diagnosed with the help of this technique in a tertiary care center in South India. Clinicoradiological features were inconclusive. Transbronchial cryo-lung biopsy helped to achieve the diagnosis.

An 8-year follow-up of IgG4-related skin disease presented with generalized ALHE-like eruptions: successful treatment of glucocorticoid and cyclophosphamide

Immunoglobulin gamma (IgG) type 4-related disease (IgG4-RD) is a chronic immunologic systemic disorder that could affect multiple organs, which may cause irreversible organ damage or even death. Skin involvement is rare and associated especially with systemic disease. The dermatologist must be equipped to recognize IgG4-RD to prevent delayed identification and treatment. This case reports a very rare case of IgG4-related skin disease (IgG4-RSD) presenting with a generalized angiolymphoid hyperplasia with eosinophilia (ALHE)-like lesions in a middle-aged male patient with no other organ involvement. He was treated with oral glucocorticoid and cyclophosphamide, which resulted in complete remission. No relapse and disease progression were seen with a follow-up for 8 years.

Infrequent organ involvement in immunoglobulin G4-related prostate disease: A case report

BACKGROUND

Immunoglobulin G4-related prostate disease (IgG4-RPD) characterized by a high count of IgG4-positive plasma cells has distinctive serological and radiological findings. Here we report a case of a patient who was successfully treated for IgG4-RPD, which manifested as frequent micturition, dysuric, and systemic lymphadenopathy.

CASE SUMMARY

The patient was a 33-year-old man who was referred to our hospital because of urinary tract symptoms that had persisted for 4 years. A physical examination revealed systemic lymphadenopathy and blood tests showed hyperglobulinemia with an IgG level of 18.90 g/L and an IgG4 level of 18.40 g/L. Computed tomography (CT) revealed bilateral lacrimal gland, right parotid gland and prostatic enlargement. Based on these findings, IgG4-RD was suspected, and further pathological examination and follow-up results showed expected results. Finally, the patient was diagnosed with IgG4-RPD based on clinical symptoms, pathological examination, therapeutic effects, and follow-up results. He received 50 mg oral prednisolone (the dose was gradually reduced and a low dose was used for long-term maintenance) in combination with cyclophosphamide 1.0 g via an intravenous drip for 6 mo. One year after the treatment was initiated, he was free of urinary or other complaints and his serum IgG4 level normalized.

CONCLUSION

In IgG4-RPD with severe urinary tract symptoms, radiological findings should be carefully examined. IgG4-RPD prognosis is good because the disease responds well to glucocorticoids. Furthermore, it is urgent for clinicians and pathologists to improve their understanding of IgG4-RPD.

Tolosa-Hunt Syndrome and IgG4 Diseases in Neuro-Ophthalmology

Tolosa-Hunt syndrome (THS) remains a challenging diagnosis for many neurologists. Often believed to be a rare presentation, the classical presentation is known to involve cranial nerves and tissues surrounding the cavernous sinus. Traditionally, a diagnosis of THS is considered when all secondary conditions have been ruled out. Yet, newer findings have elaborated a complex pathogenetic process with some overlap from the IgG4 spectrum of disorders, with which it shares many phenotypic similarities. In this narrative review, we present an updated picture of the condition focusing on the latest developments in the pathogenesis, diagnosis, and clinical management of these two conditions and use illustrative examples to highlight the salient features of this rare presentation.

Expanded CD4+CXCR5-PD-1+ peripheral T helper like cells and clinical significance in IgG4-related disease

To identify the phenotypic features and clinical significance of peripheral T helper (Tph) like cells in IgG4-RD, 54 untreated IgG4-RD patients and 57 healthy controls (HCs) were enrolled. Flow cytometry analysis, ELISA and correlation analysis were performed. Results indicated that percentages of CD4 + CXCR5-PD-1+ Tph like cells in the peripheral blood of IgG4-RD patients were significantly higher than those of HCs (2.27% ± 1.99% vs 1.12% ± 0.98%, P < 0.001). Expression of CD38, CD25, and TIGIT was higher, whereas that of CCR7, CD127 was lower in the Tph like cells from the IgG4-RD patients than in those from the HCs. The IgG4-RD patients with affected internal organs had higher circulating Tph like cell levels than those without (2.69% ±1.99% vs 1.23% ± 0.93%, respectively, P = 0.003). In addition, Tph like cells correlated with serum IgG and IgG4 and peripheral plasmablast levels which could be a promising biomarker for disease activity monitoring.

Positive disease-specific autoantibodies have limited clinical significance in diagnosing IgG4-related disease in daily clinical practice

OBJECTIVES

The 2019 ACR/EULAR classification criteria for IgG4-related disease (IgG4-RD) have exclusion criteria including positive disease-specific autoantibodies, and these have been documented to have a high specificity. This study aimed to further validate these criteria as well as identify characteristics of patients showing false-negative results.

METHODS

We retrospectively analysed 162 IgG4-RD patients and 130 mimickers. The sensitivity, specificity and fulfilment rates for each criterion were calculated, and intergroup comparisons were performed to characterize the false-negative cases.

RESULTS

Both the IgG4-RD patients and mimickers were aged ≥65 years with male predominance. The final diagnoses of mimickers were mainly malignancy, vasculitis, sarcoidosis and aneurysm. The classification criteria had a sensitivity of 72.8% and specificity of 100%. Of the 44 false-negative cases, one did not fulfil the entry criteria, 20 fulfilled one exclusion criterion and 27 did not achieve sufficient inclusion criteria scores. The false-negative cases had fewer affected organs, lower serum IgG4 levels, and were less likely to have received biopsies than the true-positive cases. Notably, positive disease-specific autoantibodies were the most common exclusion criterion fulfilled in 18 patients, only two of whom were diagnosed with a specific autoimmune disease complicated by IgG4-RD. In addition, compared with the true-positive cases, the 18 had comparable serum IgG4 levels, number of affected organs, and histopathology and immunostaining scores despite higher serum IgG and CRP levels.

CONCLUSIONS

The ACR/EULAR classification criteria for IgG4-RD have an excellent diagnostic specificity in daily clinical practice. Positive disease-specific autoantibodies may have limited clinical significance for the diagnosis of IgG4-RD.

IgG4-related disease: a great mimicker of lung cancer

IgG4-related disease is a rheumatological disorder, affecting multiple organ systems, and displaying dense lymphoplasmacytic inflammatory infiltrate and storiform fibrosis on histology. The pulmonary manifestations of IgG4-related disease are varied. Most commonly, bronchovascular consolidation and perilymphatic parenchymal thickening occur. IgG4-related disease can present as a solitary parenchymal mass and is often mistaken for a primary pulmonary or haematological malignancy. This report presents a case of IgG4-related disease in a patient with 6 months reported haemoptysis symptomatology and CT findings of perihilar lymphadenopathy, multiple pulmonary parenchymal nodules and a single parenchymal mass. Clinician cognisance of the histopathological presentation of IgG4-disease is important. It should be considered as a differential in patients for which investigations have ruled out malignancy, as it is responsive to glucocorticoids in the majority of cases.

The 2020 revised comprehensive diagnostic (RCD) criteria for IgG4-RD

IgG4-related disease (IgG4-RD) is a fascinating clinical entity first reported in this century in Japan, and includes a wide variety of diseases, such as formerly named Mikulicz's disease (MD), autoimmune pancreatitis (AIP), interstitial nephritis, prostatitis and retroperitoneal fibrosis. The Japanese IgG4 team organized by the Ministry of Health, Labor and Welfare (MHLW) of Japan has published the first criteria, comprehensive diagnostic (CD) criteria for IgG-RD 2011. Thereafter, IgG4-RD has been accepted widely and many cases have been reported from all over the world. Several problems have arisen in clinical practice, however, including the difficulty obtaining biopsy samples, and the sensitivity and specificity in cut off level of serum IgG4 and impaired immunostaining of IgG4. Given these situations, the Japanese IgG4 team has updated the 2011 comprehensive diagnostic criteria for IgG4-RD and propose the 2020 revised comprehensive diagnostic (RCD) criteria for IgG4-RD, which consists of 3 domains; 1) Clinical and radiological features, 2) Serological diagnosis and 3) Pathological diagnosis. In addition, the new pathological diagnosis is composed by three sub-items including storiform fibrosis and obliterative phlebitis.

IgG4-related disease with multiple organs involvement was effectively controlled by glucocorticoids: a case report

Immunoglobulin G4 (IgG4) related disease is a rare autoimmune disease involving multiple organs and tissues. A diagnosis of IgG4-related disease (IgG4-RD) is mainly based on serum IgG4 concentration, imaging, pathology, and effective glucocorticoids therapy. In this paper, we report a 53-year-old male with typical signs and symptoms of IgG4-RD successfully treated with glucocorticoids. This patient had experienced bilateral mumps for more than 8 months and intermittent abdominal pain spreading to his lower back for 2 months before his admission. During his hospitalization, based on the characteristic appearance of magnetic resonance imaging (MRI), magnetic resonance cholangiopancreatography (MRCP), and computed tomography with positron emission tomography, a diagnosis of autoimmune pancreatitis (AIP), cholangitis with biliary obstruction, lachrymal adenitis, and submandibular adenitis was made. A high serum IgG4 concentration further supported a diagnosis of IgG4-RD. Then, the treatment was promptly initiated with corticosteroids. MRI, MRCP, and IgG4 concentration were re-examined during his follow up, suggesting that glucocorticoid treatment resulted in a resolution of his disease. The dosage of glucocorticoid had been gradually decreased. Now, he is stable with oral low-dose glucocorticoids. Certainly, long-term follow up of this patient with such a rare disease is very essential to observe the possibility of disease recurrence and glucocorticoids related complications.

Update on IgG4-mediated autoimmune diseases: New insights and new family members

Antibodies of IgG4 subclass are exceptional players of the immune system, as they are considered to be immunologically inert and functionally monovalent, and as such may be part of classical tolerance mechanisms. IgG4 antibodies are found in a range of different diseases, including IgG4-related diseases, allergy, cancer, rheumatoid arthritis, helminth infection and IgG4 autoimmune diseases, where they may be pathogenic or protective. IgG4 autoimmune diseases are an emerging new group of diseases that are characterized by pathogenic, antigen-specific autoantibodies of IgG4 subclass, such as MuSK myasthenia gravis, pemphigus vulgaris and thrombotic thrombocytopenic purpura. The list of IgG4 autoantigens is rapidly growing and to date contains 29 candidate antigens. Interestingly, IgG4 autoimmune diseases are restricted to four distinct organs: 1) the central and peripheral nervous system, 2) the kidney, 3) the skin and mucous membranes and 4) the vascular system and soluble antigens in the blood circulation. The pathogenicity of IgG4 can be validated using our classification system, and is usually excerted by functional blocking of protein-protein interaction.

Immunological Role of IgG Subclasses

The loss of tolerance to self-antigens is the unequivocal "red line" of autoimmunity: both development of autoreactive T and B cells and production of polyclonal autoantibodies represent seminal keys to the pathogenesis of protean autoimmune diseases. Most of these autoantibodies are immunoglobulins G (IgG), functionally distinguished in four subclasses named IgG1, IgG2, IgG3, and IgG4, due to structural differences in the hinge and heavy chain constant regions. Different studies analyzed serum levels of IgG subclasses in the course of different disorders, showing that they might have a pathogenic role by regulating interactions among immunoglobulins, Fc-gamma receptors, and complement. To date, the mechanisms promoting different IgG subclasses distribution during the natural history of most autoimmune diseases remain somewhat unclear. Evidence from the medical literature shows that the serum IgG profile is peculiar for many autoimmune diseases, suggesting that different subclasses could be specific for the underlying driving autoantigens. A better knowledge of IgG subsets may probably help to elucidate their pathological task, but also to define their relevance for diagnostic purposes, patients' personalized management, and prognosis assessment.

[Idiopathic multicentric Castleman's disease]

Idiopathic multicentric Castlemans disease is a rare lymphoproliferative disorder that has many similar laboratory, radiological, clinical and pathological manifestations with various conditions, including IgG4-related disease. Increased activity of cytokines, especially interleukin-6, leads to systemic inflammatory symptoms with the development of lymphadenopathy and rarely extranodal lesions. Histological changes in the lymph nodesin hyaline vascular and plasma cell variants of Castlemans disease are hardly distinguishable from the pattern of reactive, tumor and IgG4-related lymphadenopathy. Idiopathic multicentric Castlemans disease can be diagnosed only when infection with human herpesvirus-8 type and human immunodeficiency virus is excluded. In the article, the authors describe two cases of idiopathic multicentric Castlemans disease, including the first world literature description of extranodal damage of the hip muscle in this disorder. In addition, the authors gave a review of the literature on the main clinical, laboratory and morphological manifestations, which allow confirming the diagnosis of Castlemans disease.

Consideration concerning similarities and differences between ANCA-associated vasculitis and IgG-4-related diseases: case series and review of literature

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and immunoglobulin G4-related diseases (IgG4-RD) are regarded as entirely different disease types with different etiological mechanisms. However, we experienced two cases that had clinical features of both AAV and IgG4-RD. The first case is an 81-year-old woman who showed periaortitis and retroperitoneal fibrosis and periarteritis with elevation of myeloperoxidase-anti-neutrophil cytoplasmic antibody and IgG4 levels. The second case is a 63-year-old woman who had dura mater, ear, nose, lung, and kidney involvement with serum negative for ANCA and elevated IgG4. Renal biopsy revealed tubulointerstitial nephritis involving IgG4⁺ plasma cells (IgG4⁺/IgG⁺ cell ratio of ≥ 40%). On the other hand, lung biopsy showed features of granulomatosis with polyangiitis (GPA). These two cases suggested that AAV and IgG4-RD might overlap. To investigate the similarities and differences between AAV and IgG4-RD, we retrospectively analyzed 13 cases of typical GPA, a subtype of AAV, and 13 cases of typical IgG4-RD at our hospital for comparison of clinical features and found some differences that can be useful in the differential diagnosis between the two diseases. Although AAV and IgG4-RD are distinguishable based on characteristic findings in many cases, the diagnosis can be unclear in rare cases, in which clinicians should consider possible coexistence of AAV and IgG4-RD when performing further workup. Here, we discuss the similarities and differences between AAV and IgG4-RD on the basis of our results and past literature.

Impaired expression of innate immunity-related genes in IgG4-related disease: A possible mechanism in the pathogenesis of IgG4-RD

Background: IgG4-related disease (IgG4-RD) is characterized by elevated serum IgG4 and tissue infiltration by IgG4-positive plasma cells. The pathogenesis of this disease is not clear. Transcriptome analysis was performed to identify genes over- and under-expressed in patients with IgG4-RD.Method: DNA microarray analysis was performed using RNA from peripheral blood mononuclear cells of two patients with IgG4-RD and four healthy individuals. Genes showing a greater than threefold change in expression in IgG4-RD patients following steroid therapy were identified. Four genes related to innate immunity such as transcobalamin I (TCN1), secretory leukocyte peptidase inhibitor (SLPI), bactericidal/permeability-increasing protein (BPI) and lactotransferrin (LTF) were assessed by real-time PCR in 15 IgG4-RD patients and 13 healthy individuals.Result: DNA microarray analysis identified 30 genes showing a greater than threefold change in expression in IgG4-RD patients following steroid therapy. Real-time RT-PCR showed that the levels of mRNAs encoding TCNI and SLPI, except for BPI and LTF, were significantly lower in patients with IgG4-RD than in healthy people. The levels of all four mRNAs in patients with IgG4-RD were significantly increased after steroid treatment.Conclusion: These results indicate that reduction in expression of innate immunity-related genes may participate in the pathogenesis of IgG4-RD that steroid treatment may rectify impaired innate immunity as well as acquired immunity.

A rare case of oral tumor presenting as first sign of immunoglobulin G4-related disease

Immunoglobulin G4 (IgG4)-related disease is an idiopathic autoimmune disease characterized by elevated serum and tissue IgG4 levels, organ enlargement, and a clinical response to immunosuppressants. We present such a case in a 39-year-old female, whose lesion was located in the right buccal space involving the minor salivary gland. After the tumorlike growth was removed, diagnosis was confirmed with histopathologic slides showing lymphoid cell infiltration, dense fibrotic stroma, and IgG4-positive plasma cells. The patient underwent steroid therapy, and there has been no recurrence since. Rarely do we see IgG4-related sclerosing disease involve the buccal minor salivary gland in its early stages. Thus, it is important to include IgG4-related disease in the differential diagnosis when considering autoimmune diseases with oral manifestations.

The pancreatic and extrapancreatic manifestations of IgG4-related disease

The association between immunoglobulin IgG4 and autoimmune pancreatitis was first shown in 2001. Since then many previously established fibrosclerotic diseases demonstrating synchronous or metachronous multiorgan involvement have been included within the ambit of IgG4-related disease. Diagnostic criteria have been proposed involving 1) serum IgG4 level elevated beyond 135 mg/dL, 2) IgG4+ to IgG+ plasma cell ratio > 40% and >10 IgG4+ cells per high power field of biopsy sample and 3) a constellation of imaging features which involve a variety of organ systems. We present a pictorial essay demonstrating the spectrum of imaging findings for IgG4-related disease, including dacryosialadenitis, variety of renal lesions, tumefactive thickening of the extraocular muscles and orbital nerve, sclerosing cholangitis, and type I pancreatitis. Imaging plays an important role in diagnosis, screening for multiorgan involvement, and follow-up of the disease.

IgG4-Related Disease: Beyond Glucocorticoids

IgG4-related disease is a heterogeneous immune-mediated fibroinflammatory condition that can affect every single organ. This disease is more prevalent in the elderly (the mean age of patients is above 60 years) and the prevalence rate is estimated to be over 4.6 per 100,000 population. Before making a diagnosis, the exclusion of malignancies, lymphoma, anti-neutrophil cytoplasmic antibody-associated vasculitis, multicentric Castleman disease, and other mimickers is crucial for appropriate treatment. Broad management guidelines have been published emphasizing the need for prompt treatment and the use of glucocorticoids as first-line drug therapy for induction of remission. However, the toxic effects of glucocorticoids are problematic because IgG4-related disease is more prevalent in patients above 60 years of age, a population with frequent comorbid conditions and polypharmacy. Immunosuppressants (cyclophosphamide, methotrexate, leflunomide, and tacrolimus) and targeted immunomodulators (rituximab, XmAb5871, and abatacept) are appealing to overcome potential toxic effects of glucocorticoids and as emerging glucocorticoid-sparing and/or maintenance treatments. In this review, we provide an overview of our understanding of the pathophysiology of the disease (T follicular helper cells, CD4⁺ cytotoxic T cells, plasmablasts, and alternatively activated M2 macrophages) and clinical characteristics, and highlight the potential targets for treatment intervention.

A New Classification System for IgG4 Autoantibodies

IgG4 autoimmune diseases are characterized by the presence of antigen-specific autoantibodies of the IgG4 subclass and contain well-characterized diseases such as muscle-specific kinase myasthenia gravis, pemphigus, and thrombotic thrombocytopenic purpura. In recent years, several new diseases were identified, and by now 14 antigens targeted by IgG4 autoantibodies have been described. The IgG4 subclass is considered immunologically inert and functionally monovalent due to structural differences compared to other IgG subclasses. IgG4 usually arises after chronic exposure to antigen and competes with other antibody species, thus "blocking" their pathogenic effector mechanisms. Accordingly, in the context of IgG4 autoimmunity, the pathogenicity of IgG4 is associated with blocking of enzymatic activity or protein-protein interactions of the target antigen. Pathogenicity of IgG4 autoantibodies has not yet been systematically analyzed in IgG4 autoimmune diseases. Here, we establish a modified classification system based on Witebsky's postulates to determine IgG4 pathogenicity in IgG4 autoimmune diseases, review characteristics and pathogenic mechanisms of IgG4 in these disorders, and also investigate the contribution of other antibody entities to pathophysiology by additional mechanisms. As a result, three classes of IgG4 autoimmune diseases emerge: class I where IgG4 pathogenicity is validated by the use of subclass-specific autoantibodies in animal models and/or in vitro models of pathogenicity; class II where IgG4 pathogenicity is highly suspected but lack validation by the use of subclass specific antibodies in in vitro models of pathogenicity or animal models; and class III with insufficient data or a pathogenic mechanism associated with multivalent antigen binding. Five out of the 14 IgG4 antigens were validated as class I, five as class II, and four as class III. Antibodies of other IgG subclasses or immunoglobulin classes were present in several diseases and could contribute additional pathogenic mechanisms.

Surgical management of isolated mesenteric autoimmune disease: addressing the spectrum of IgG4-related disease and sclerosing mesenteritis

IgG₄-related disease (IgG₄-RD) is a rare form of autoimmune sclerosing disease, characterised by elevated serum IgG₄ and tissue IgG₄ levels, specific histopathological findings, multiorgan involvement and adequate response to glucocorticoid treatment. The low incidence and the heterogeneous nature of the disease has made consensus on diagnostic criteria for IgG₄-RD difficult. Whether sclerosing mesenteritis (SM) is considered a manifestation of IgG₄-RD is strongly debated. We present the case of a patient with a history of rheumatoid arthritis who presented with a calcified abdominal mass. She was found to have an isolated, pedunculated mesenteric mass positive for IgG₄ and concurrently elevated serum IgG₄ levels. Clinical features did not classify her disease as either SM or IgG₄-RD as currently described in consensus statements. Concurrent diagnoses of IgG₄-RD, SM and other autoimmune disorders, as well as postoperative recommendations for resected isolated IgG₄-positive masses, are discussed.