Identifying clinical subgroups in IgG4-related disease patients using cluster analysis and IgG4-RD composite score

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.

Implication of allergy and atopy in IgG4-related disease

Immunoglobulin G4-related disease (IgG4-RD) is a chronic multi-organic immune fibrosing disease. It affects preferentially men around middle age and almost any organs can be involved; however, lymph nodes, submandibular and lacrimal glands, pancreas, and retroperitoneum are the most affected. The mainstay treatment is corticosteroids, sometimes adjuncts with DMARDs or rituximab as steroid sparing agents. Th2 inflammation is implicated in the pathophysiology of the disease. Several reports indicate that allergy and/or atopy often affect patients with IgG4-RD. The frequency varies greatly between studies with allergies/allergic diseases reported in 18-76% while atopy is reported in 14-46%. In studies including both, they affect 42 and 62% of patients. Rhinitis and asthma are the most frequent allergic diseases. IgE and blood eosinophiles are often elevated and few studies report that basophils and mast cells could participate in the disease pathogenesis; however, the implication of allergy and atopy remain unclear. No common allergen has been identified and IgG4 production seems to be polyclonal. Although a direct causal effect is unlikely, they could potentially shape the clinical phenotype. Allergies/allergic diseases and/or atopy are reported to be more frequent in IgG4-RD patients presenting head, neck, and thoracic involvement, with higher IgE and eosinophils and less frequent in retroperitoneal fibrosis; however, studies regarding allergy and atopy in IgG4-RD are highly heterogenous. The aim of this article is to review what is currently known about the allergy and atopy in the context of Ig4-RD.

Correlation between serologic parameters and disease activity of IgG4-related disease: Differences between patients with normal and elevated serum IgG4 concentrations

Objective

We aimed to identify serologic parameters that correlate with the disease activity of IgG4-related disease (IgG4-RD) in patients with normal and elevated serum IgG4 concentrations, respectively.

Methods

This retrospective cohort study included 148 patients with IgG4-RD. Patients were categorized into normal (≤201 mg/dL) and elevated (>201 mg/dL) serum IgG4 concentration groups. Disease activity was assessed using the IgG4-RD responder index (RI). The correlations between IgG4-RD RI and serologic parameters (erythrocyte sedimentation rate [ESR], C-reactive protein, C3, C4, IgG4 concentration, IgG concentration, and IgG4/IgG ratio) were evaluated in each group, using Spearman’s correlation coefficient.

Results

Of the 148 patients with IgG4-RD, 38 (25.7%) and 110 (74.3%) patients were categorized into the normal and elevated serum IgG4 concentration groups, respectively. In the normal serum IgG4 concentration group, IgG concentration was the only serologic parameter that showed a significant correlation with IgG4-RD RI (rho=0.411, p=0.013). However, in the elevated serum IgG4 concentration group, ESR (rho=0.196, p=0.041), C3 (rho=-0.432, p<0.001), C4 (rho=-0.363, p=0.001), IgG4 concentration (rho=0.423, p<0.001), IgG concentration (rho=0.224, p=0.020), and IgG4/IgG ratio (rho=0.328, p=0.001) correlated with IgG4-RD RI. The combination of C3 and IgG4 concentration (rho=0.509, p<0.001) had the strongest correlation with IgG4-RD RI in this group.

Conclusion

Among the serologic parameters tested, IgG concentration was the only parameter that correlated with IgG4-RD RI in patients with normal serum IgG4 concentrations, whereas multiple parameters correlated with IgG4-RD RI in those with elevated serum IgG4 concentrations. The combination of C3 and IgG4 concentration had the strongest correlation coefficient in the latter group.

Radiological Determinants of Complicated Immunoglobulin G4-Related Ophthalmic Disease: A Territory-Wide Cohort Study

PURPOSE

To evaluate the presenting radiological features of immunoglobulin G4-related ophthalmic disease (IgG4-ROD) and their associations with IgG4-related optic neuropathy (IgG4-RON), and IgG4-related ocular adnexal lymphoma (IgG4-ROL).

METHODS

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

RESULTS

A total of 115 (94%) of the 122 patients in our cohort had preoperative orbital images (computed tomography=105, magnetic resonance imaging=40). Among them, 103/115 (90%) showed enlarged lacrimal glands, and 91 (88%) were bilateral. Nerve enlargement was observed: infraorbital in 31/115 (27%) patients and frontal in 17/115 (15%), 10 and 9 being bilateral, respectively. At least 1 or more extraocular muscle (EOM) enlargement was found in 41/115 (37%) patients, bilaterally in 20. Lateral rectus occurred in 30 (73%) of these 41 EOM patients and inferior rectus in 28 (68%). Two adjacent EOMs (inferior and lateral recti in 11 patients, inferior and medial recti in 7 patients) or multiple EOMs (at least 3) were enlarged in 23/41 (56%) and 13/41 (32%) of the patients, respectively. Intraconal lesions (67% vs 11%, P<0.05), infraorbital (83% vs 23%, P<0.005), or frontal (50% vs 15%, P<0.05) nerve enlargement was significantly associated with IgG4-RON (6 patients) by univariate analyses. Asymmetric lacrimal gland enlargement and discrete orbital mass (both P<0.05) were associated with IgG4-ROL (9 patients) by multivariate analyses.

CONCLUSIONS

In this IgG4-ROD cohort, most patients had bilateral enlarged lacrimal glands, and the lateral rectus is the most frequently involved EOM. For the first time, unique radiological patterns associated with the development of IgG4-RON and IgG4-ROL are found.

Prediction of new organ onset in recurrent immunoglobulin G4-related disease during 10 years of follow-up

OBJECTIVE

Frequent relapse is a prominent challenge in managing immunoglobulin G4-related disease (IgG4-RD). According to the types of organs involved in relapse, relapse patterns were divided into recurrent organ involvement (ROI) and new organ involvement (NOI). We aimed to investigate the discrepancy in clinical relapse patterns and establish an effective prognostic nomogram for NOI.

METHODS

We retrospectively enrolled 125 IgG4-RD patients who experienced relapse during the follow-up period. Patients were classified into two groups: those with NOI (including NOI and NOI + ROI) and without NOI (ROI). Logistic regression analyses were used to assess the risk factors for NOI. The results were externally validated by a separate prospective cohort of 39 patients with relapse.

RESULTS

There were 81 (64.8%) and 44 (35.2%) patients without NOI and with NOI, respectively. Patients without NOI showed higher baseline disease activity. The most common ROIs were the lacrimal gland and submandibular gland, while the lung and urinary system were the most involved in NOI. Re-elevation of serum IgG4 level to 74.31% of baseline was associated with NOI. Multiple relapses, organ involvement type at baseline, glucocorticoids combined with immunosuppressive drugs (IM) or IM alone during the maintenance period, and relapse IgG4/baseline IgG4 ratio were included in the nomogram. Both internal and external validations showed good agreement and discrimination.

CONCLUSIONS

About one third of IgG4-RD patients with relapse suffer from NOI. We developed a risk stratification model that can effectively predict the future risk of NOI. Glucocorticoid and IM combined therapy during maintenance is also recommended.

Retroperitoneal fibrosis, a rare entity with urorenal and vascular subtypes - preliminary data

Introduction

Retroperitoneal fibrosis (RPF) is a rare disease associated with the formation of hard inflammatory and fibrous tissue in the retroperitoneum. Taking into consideration the fact that RPF is a rare disease with different subtypes, we compared the basal clinical and biochemical characteristics of the vascular and urorenal subtypes.

Patients and methods

From January 2005 until December 2021, 27 patients were identified as vascular subtype (18 males) and 11 as urorenal subtype (9 males).

Results

Patients with a primary urorenal origin had significantly worse kidney function as reflected by serum creatinine and eGFR (both p < 0.001); they also had higher serum cholesterol (p < 0.01). Hypertension, diabetes, hyperlipidemia and nicotinism were significantly more prevalent in vascular subtype (all p < 0.001).

Conclusion

Vascular subtype is more prevalent in our study with more cardiovascular risk factor present. Due to the diversity of symptoms, diagnosis of RPF becomes a challenge for specialists as well as therapy.

Abnormal [18F]fluorodeoxyglucose accumulation to tori tubarius in IgG4-related disease

OBJECTIVES

Tubarial glands (TGs) are recently refocused gland tissues localized near the tori tubarius in the nasopharynx and their clinical relevance is not clear yet. IgG4-related disease (IgG4-RD) is a progressive fibrosing condition and salivary glands are well-affected lesions. The aim of the present study is to examine [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) accumulation to the tori tubarius in IgG4-related disease (IgG4-RD).

METHODS

48 patients with IgG4-RD who underwent positron emission tomography (PET) scanning with [¹⁸F]FDG were included and semi-quantitative analysis of [¹⁸F]FDG accumulation to tori tubarius was performed along with the clinical features and histopathological analysis.

RESULTS

Of the 48 patients, abnormal [¹⁸F]FDG accumulation (metabolic tumour volume ≥ 1) to tori tubarius was observed in 15 (31.3%), all of whom had lesions in other head and neck glands. IgG4-RD patients with abnormal [¹⁸F]FDG accumulation to tori tubarius showed swollen nasopharyngeal walls around tori tubarius and forceps biopsy of the lesion revealed acinar cells and IgG4-positive plasma cells histologically. Abnormal [¹⁸F]FDG accumulation (maximum standard uptake value, metabolic tumour volume and total lesion glycolysis) to tori tubarius correlated with higher IgG4 and lower IgA serum concentrations.

CONCLUSIONS

Abnormal [¹⁸F]FDG accumulation to tori tubarius can be observed in patients with IgG4-RD and the abnormal [¹⁸F]FDG accumulation to tori tubarius can be a clue of TG involvement in IgG4-RD.

Peripheral B-Cell Immunophenotyping Identifies Heterogeneity in IgG4-Related Disease

Objectives

To elucidate heterogeneity of IgG4-related disease (IgG4-RD) based on B cell immunophenotyping.

Methods

Immunophenotyping of 4 B-cell subsets in peripheral blood from patients with active IgG4-RD (aIgG4-RD, n=105) was performed using flow cytometry to get preliminary B-cell heterogeneity spectrum. Then 10 B-cell subsets were characterized in aIgG4-RD (n = 49), remissive IgG4-RD (rIgG4-RD, n = 49), and healthy controls (HCs, n = 47), followed by principal components analysis (PCA) and cluster analysis to distinguish B-cell immunophenotypes and classify IgG4-RD patients into subgroups.

Results

Cluster analysis identified two endotypes in 105 aIgG4-RD patients based on 4 B-cell subsets: Group1 with higher Breg and naive B cells (n = 48), and Group2 with higher plasmablasts and memory B cells (MBCs) (n = 57). PCA indicated that aIgG4-RD consisted of plasmablast-naive B cell and MBCs-Breg axes abnormalities. There was a negative relationship between naive B cells and disease activity. Both plasmablasts and MBCs were positively associated with serological biomarkers. Cluster analysis stratified aIgG4-RD patients into 3 subgroups based on 10 B-cell subsets: subgroup1 with low MBCs and normal Breg, subgroup2 with high MBCs and low Breg, and subgroup3 with high plasmablasts and low naive B cells. Patients in subroup2 and subgroup3 were more likely to be resistant to treatment.

Conclusion

Patients with aIgG4-RD can be divided into 3 subgroups based on B cell heterogeneity. The B cell immunophenotyping could help elucidate the pathogenesis of IgG4-RD, identify patients with potential refractory IgG4-RD, and provide important information for the development of new therapies.

Longitudinal analysis of symptom-based clustering in patients with primary Sjogren's syndrome: a prospective cohort study with a 5-year follow-up period

BACKGROUND

Sjogren's syndrome (SS) is a heterogenous disease with various phenotypes. We aimed to provide a relevant subclassification based on symptom-based clustering for patients with primary (p) SS.

METHODS

Data from patients in a prospective pSS cohort in Korea were analysed. Latent class analysis (LCA) was performed using patient reported outcomes, including pain, fatigue, dryness, and anxiety/depression. Clinical and laboratory differences between the classes were analysed. Latent transition analysis (LTA) was applied to the longitudinal data (annually for up to 5 years) to assess temporal stability of the classifications.

RESULTS

LCA identified three classes among 341 patients with pSS (i.e., 'high symptom burden', 'dryness dominant', 'low symptom burden'). Each group had distinct laboratory and clinical phenotypes. LTA revealed that class membership remained stable over time. Baseline class predicted future salivary gland function and damage accrual represented by a Sjogren's syndrome disease damage index.

CONCLUSION

Symptom-based clustering of heterogenous patients with primary Sjogren's syndrome provided a relevant classification supported by temporal stability over time and distinct phenotypes between the classes. This clustering strategy may provide more homogenous groups of pSS patients for novel treatment development and predict future phenotypic evolvement.

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

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