Incidence, prevalence and mortality of IgG4-related disease in the USA: a claims-based analysis of commercially insured adults

IgG4-related disease-rare but you should not forget it

Immunoglobulin G4-related disease is a systemic immune-mediated disease with insidious evolution characterized by fibroinflammatory lesions over virtually any organ system. Despite the remarkable progression of knowledge, its etiology remains undefined. Due to its relapse-remitting pattern, it could accumulate irreversible damage, increasing comorbidities and mortality. This paper emphasizes key concepts for diagnosing and treating patients with this condition.

Type 1 Autoimmune Pancreatitis in Europe: Clinical Profile and Response to Treatment

BACKGROUND & AIMS

Autoimmune pancreatitis (AIP) is an immune-mediated disease of the pancreas with distinct pathophysiology and manifestations. Our aims were to characterize type 1 AIP in a large pan-European cohort and study the effectiveness of current treatment regimens.

METHODS

We retrospectively analyzed adults diagnosed since 2005 with type 1 or not-otherwise-specified AIP in 42 European university hospitals. Type 1 AIP was uniformly diagnosed using specific diagnostic criteria. Patients with type 2 AIP and those who had undergone pancreatic surgery were excluded. The primary end point was complete remission, defined as the absence of clinical symptoms and resolution of the index radiologic pancreatic abnormalities attributed to AIP.

RESULTS

We included 735 individuals with AIP (69% male; median age, 57 years; 85% White). Steroid treatment was started in 634 patients, of whom 9 (1%) were lost to follow-up. The remaining 625 had a 79% (496/625) complete, 18% (111/625) partial, and 97% (607/625) cumulative remission rate, whereas 3% (18/625) did not achieve remission. No treatment was given in 95 patients, who had a 61% complete (58/95), 19% partial (18/95), and 80% cumulative (76/95) spontaneous remission rate. Higher (≥0.4 mg/kg/day) corticosteroid doses were no more effective than lower (<0.4 mg/kg/day) doses (odds ratio, 0.428; 95% confidence interval, 0.054-3.387) and neither was a starting dose duration >2 weeks (odds ratio, 0.908; 95% confidence interval, 0.818-1.009). Elevated IgG4 levels were independently associated with a decreased chance of complete remission (odds ratio, 0.639; 95% confidence interval, 0.427-0.955). Relapse occurred in 30% of patients. Relapses within 6 months of remission induction were independent of the steroid-tapering duration, induction treatment duration, and total cumulative dose.

CONCLUSIONS

Patients with type 1 AIP and elevated IgG4 level may need closer monitoring. For remission induction, a starting dose of 0.4 mg/kg/day for 2 weeks followed by a short taper period seems effective. This study provides no evidence to support more aggressive regimens.

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.

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.

Challenges and pitfalls in the diagnosis of IgG4-related disease

IgG4-related disease (IgG4-RD) is a relatively novel fibroinflammatory condition characterized typically by dense lymphoplasmacytic inflammation, storiform fibrosis and obliterative venulitis, together with prominent IgG4+ plasma cells and an IgG4+/IgG+ plasma cell ratio of >40 %. The diagnosis is usually made on a combination of clinical and serological features together with characteristic radiological and histological appearances. The condition may be limited to a single tissue/organ (e.g., autoimmune pancreatitis) or may be multicentric in nature - four clinical 'patterns' of disease distribution have recently been described. The diagnosis of IgG4-RD can be challenging, particularly when the clinical presentation is unusual and/or when the histological features are not typical. A diagnosis of IgG4-RD may still be achieved in these situations, after careful clinicopathological discussion e.g., at a specialist multidisciplinary team meeting. However, a wide range of other conditions (neoplastic and non-neoplastic) can mimic IgG4-RD, clinically and/or on histological examination. The relationship between IgG4-RD and non-IgG4-RD associated conditions in some clinical situations is particularly complex. This review describes the role of histological examination in the diagnosis of IgG4-RD, discusses some of the practical difficulties that may be encountered and provides an insight into the range of non-IgG4-RD associated conditions that can mimic IgG4-RD on clinical and/or histological grounds. The requirement for interpretation of histological features in the context of the global clinical picture of the patient is highlighted and emphasized.

Myofibroblast and pro-fibrotic cytokines in fibrosis of IgG4-related disease (IgG4-RD) patients from South Asia: preliminary data

INTRODUCTION

Fibrosis is a typical pathological characteristic in IgG4-RD patients and often irreversible. There exists a lack of suitable markers for detection of earlier onset of fibrosis in various organs in IgG4-RD patients. Hence, this study aims at analysing ambispectively the myofibroblasts and the pro-fibrotic cytokines, IFN gamma and IL-33 involved in IgG4-RD associated fibrosis in South Asian patients.

METHOD

Archived biopsy samples of definite/probable/possible cases of IgG4-RD, classified according to diagnostic criteria, taken from patients who attended the OPD and IPD of our tertiary care centre during January 2015-January 2020 were chosen for this study. The paraffin sections were examined qualitatively for fibrosis and the excessive collagen deposition by Hematoxylin & Eosin and Masson's Trichrome staining. Also, the presence of alpha-Smooth muscle actin (α-SMA) expressing myofibroblasts and the involvement of pro-fibrotic cytokines (IFN-gamma, IL-33) were assessed by Immunohistochemistry and scored semi-quantitatively (+mild, ++moderate, +++ severe). Serum IL-33 levels were analysed by indirect Elisa (R & D Systems).

RESULTS

Myofibroblasts were present in 10/12 biopsy samples, in moderate levels in 4 (33%) and very high levels (+++) in 3 (25%) of the patients. IFN-gamma was expressed at low levels in 6 (50%) and absent in 6 (50%). All patients showed IL-33 expression with very high levels in tissue (6, 50%), as well as in serum samples.

CONCLUSION

The findings of this study reinforce the role of myofibroblasts and profibrotic cytokines like IL-33 in fibrosis of Ig4-RD patients, pointing to their potential as earlier predictive markers of onset and extent of fibrosis.

Brief research report: impact of vaccination on antibody responses and mortality from severe COVID-19

Introduction

While it is established that vaccination reduces risk of hospitalization, there is conflicting data on whether it improves outcome among hospitalized COVID-19 patients. This study evaluated clinical outcomes and antibody (Ab) responses to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection/vaccines in patients with acute respiratory failure (ARF) and various comorbidities.

Methods

In this single-center study, 152 adult patients were admitted to Ohio State University hospital with ARF (05/2020 - 11/2022) including 112 COVID-19-positive and 40 COVID-19-negative patients. Of the COVID-19 positive patients, 23 were vaccinated for SARS-CoV-2 (Vax), and 89 were not (NVax). Of the NVax COVID-19 patients, 46 were admitted before and 43 after SARS-CoV-2 vaccines were approved. SARS-CoV-2 Ab levels were measured/analyzed based on various demographic and clinical parameters of COVID-19 patients. Additionally, total IgG4 Ab concentrations were compared between the Vax and NVax patients.

Results

While mortality rates were 36% (n=25) and 27% (n=15) for non-COVID-19 NVax and Vax patients, respectively, in COVID-19 patients mortality rates were 37% (NVax, n=89) and 70% (Vax, n=23). Among COVID-19 patients, mortality rate was significantly higher among Vax vs. NVax patients (p=0.002). The Charlson's Comorbidity Index score (CCI) was also significantly higher among Vax vs. NVax COVID-19 patients. However, the mortality risk remained significantly higher (p=0.02) when we compared COVID-19 Vax vs. NVax patients with similar CCI score, suggesting that additional factors may increase risk of mortality. Higher levels of SARS-CoV-2 Abs were noted among survivors, suggestive of their protective role. We observed a trend for increased total IgG4 Ab, which promotes immune tolerance, in the Vax vs. NVax patients in week 3.

Conclusion

Although our cohort size is small, our results suggest that vaccination status of hospital-admitted COVID-19 patients may not be instructive in determining mortality risk. This may reflect that within the general population, those individuals at highest risk for COVID-19 mortality/immune failure are likely to be vaccinated. Importantly, the value of vaccination may be in preventing hospitalization as opposed to stratifying outcome among hospitalized patients, although our data do not address this possibility. Additional research to identify factors predictive of aberrant immunogenic responses to vaccination is warranted.

Extensive, circumferential, epidural spinal cord compression by IgG4-related pachymeningitis

A rare case of IgG4-related pachymeningitis is presented. The manuscript describes the multidisciplinary treatment of a rare entity in an exceptional location, prompting emergent surgical treatment. However, the correct intraoperative hypothesis led to a minimal surgical approach with fewer risks and good disease control. Finding a balance between maximising treatment outcome and minimising risks is often difficult for clinicians worldwide who encounter the same clinical dilemma. The known cases are summarised, as are radiological characteristics and common treatments.

[IgG4-related disease: A proteiform pathology with frequent chest manifestations]

INTRODUCTION

While IgG4-related disease (IgG4-RD) was initially described in the early 2000s, its polymorphic clinical manifestations were previously reported under different names ; they have in common the presence of IgG4+ oligoclonal plasma cells and fibrosis.

STATE OF THE ART

Ruling out certain differential diagnoses, the diagnosis of IgG4-RD is based on a bundle of clinical, biological and histological features. Chest involvement is variable and can affect the mediastinum, bronchi, parenchyma, pleura and/or, more rarely, bones and (pericardium, aorta, coronary…) vascular structures. The most frequent radiological manifestations are peribronchovascular thickening, mediastinal lymphadenopathy, and nodular or interstitial patterns. Pleural involvement and posterior mediastinal fibrosis are less frequent, while thoracic paravertebral tissue thickening is highly specific. Systemic corticosteroids are the cornerstone of treatment. In case of relapse or as frontline therapy in case of risk factors for relapse and/or poor tolerance of corticosteroids), a steroid-sparing agent (most often rituximab) is added, and biannual maintenance infusions are associated with a lower risk of relapse.

PERSPECTIVES

An international consensus has recently led to the development of classification criteria that should standardize the diagnostic approach and homogenize the enrolment of patients in epidemiological as well as therapeutic studies. Other treatments are also under evaluation, including biologics targeting T2 inflammation, CD-19 (inebilizumab, obexelimab), SLAMF7 (elotuzumab) surface proteins, Bruton's tyrosine kinase, and the JAK/STAT pathway.

CONCLUSIONS

Substantial progress has been made over recent years in understanding IgG4-RD pathophysiology, and personalized patient care seems to be an achievable medium-term goal.

[Swelling of the salivary glands and sicca symptoms in Kimura's disease, a rare rheumatological differential diagnosis with an indicatively high IgE serum level-A current overview after literature search]

Rheumatic and musculoskeletal diseases (RMD) include various diseases with sometimes rather different symptoms, some of which are locally confined and others show systemic features. Autoimmune phenomena, such as those occurring in Sjögren's syndrome, often cause symptoms such as xerostomia and xerophthalmia in association with inflammation of the salivary glands. The pathogenesis of these diseases is only partly clarified. This is similar to allergic diseases, which are otherwise clearly different with respect to the symptoms and pathomechanisms but swelling of the salivary glands can also rarely occur here. As this is a possible differential diagnosis of Sjögren's syndrome or also IgG4-associated diseases, and such a case was recently described, a literature search was carried out in PubMed, the results of which are presented here and summarized in this article in a brief overview.

Single-Cell RNA-Sequencing Reveals Peripheral T Helper Cells Promoting the Development of IgG4-Related Disease by Enhancing B Cell Activation and Differentiation

Abnormal B cell differentiation plays a critical role in IgG4-related disease (IgG4-RD), but the underlying mechanism remains largely unknown. We investigated the cell landscape from three IgG4-RD retroperitoneal tissues and three control tissues using single-cell RNA-sequencing. Critical cell type or markers were further validated in the peripheral blood from the patients with IgG4-RD and healthy controls via flow cytometry as well as in the IgG4-RD and control tissue via immunofluorescence staining. The increases in B cells, plasma cells, and CD4+ T cells were found in IgG4-RD retroperitoneal tissue. Importantly, among CD4+ T cells, an increase in CD4+CXCR5-PD1hi peripheral T helper (Tph) cells with a high expression of IL-21 and TIGIT was discovered in IgG4-RD tissue, which was further validated in peripheral blood of the patients with IgG4-RD. The Tph cell and TIGIT+ Tph cell proportion were remarkably higher in active IgG4-RD patients and correlated with disease activity. Moreover, TIGIT+CD4+ cells were able to promote B cell differentiation via IL-21. Our study revealed that Tph cells are increased in IgG4-RD and probably play critical roles in B cell differentiation through TIGIT-IL-21 axis. Peripheral Tph cell and TIGIT+Tph cell are potential markers for IgG4-RD disease activity.