Pathogenesis of IgG4-related disease: a critical review

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.

Nivolumab Therapy in Lung Cancer Associated with IgG4-related Disease

A 75-year-old man with severe bilateral pleural thickening and dense soft tissue masses surrounding the abdominal aorta on computed tomography was diagnosed with IgG4-related disease (IgG4-RD) as a complication of lung cancer. He was started on nivolumab as second-line therapy along with low-dose prednisolone. Nivolumab was administered for 15 months until disease progression, during which time IgG4-RD did not relapse, and no problematic immune-related adverse events occurred. These results suggest that anti-programmed cell death protein-1 antibody may be used safely in lung cancer associated with IgG4-RD concomitantly with low-dose steroids.

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.

IgG4-related retroperitoneal fibrosis: A case report of a challenging disease

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is a multi-organ immune-mediated fibroinflammatory disorder that may imitate malignancy, infectious or any other inflammatory disorder. IgG4-related retroperitoneal fibrosis (IgG4-RPF) is a rare form of IgG4-RD, diagnosis of which is often relied on radiological technology. Herein, we describe a case of 60 year old male, presenting with low back pain and weight loss for a period of 2 months and 15 days. Imaging studies showed a retroperitoneal tumorous mass along with bilateral hydroureteronephrosis, which was later confirmed to be IgG4-related retroperitoneal fibrosis on the basis of extensive histopathological analysis. Immunosuppressive therapy resulted in a decrease in fibrosis and restoration of renal function.

IgG4-related Disease Emerging after COVID-19 mRNA Vaccination: A Case Report

A 78-year-old Japanese woman with no history of rheumatic disease received 2 doses of the BNT162b2 COVID-19 mRNA vaccine. Two weeks later, she noticed bilateral swelling in the submandibular region. Blood tests showed hyper-immunoglobulin (Ig)G4emia, and ¹⁸F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) revealed the strong accumulation of FDG in the enlarged pancreas. She was diagnosed with IgG4-related disease (IgG4-RD) according to the American College of Rheumatology (ACR)/the European League Against Rheumatism (EULAR) classification criteria. Treatment was started with prednisolone at 30 mg/day, and the organ enlargement improved. We herein report a case of IgG4-RD that may have been associated with an mRNA vaccine.

Lymph Nodes With Increased IgG4-positive Plasma Cells and Patterns Suspicious for IgG4-related Disease: Can Lymph Nodes Be the Only Site of Disease?

Lymphadenopathy with increased immunoglobulin (Ig) G4 + plasma cells can be a nonspecific finding or a manifestation of immunoglobulin G4-related disease (IgG4-RD). It remains unclear whether there are characteristic pathologic features of IgG4-RD involving lymph nodes, or if IgG4-RD lymphadenopathy can occur without other manifestations of IgG4-RD. In this study, we assessed 55 lymph node biopsy specimens (44 men and 11 women with a mean age of 55 y) with increased IgG4 + plasma cells that had 1 of the 6 well-described pathologic patterns. We also correlated these findings with IgG4 serum levels and followed these patients for 7 to 108 months (mean, 34.9 mo) for the occurrence of extranodal IgG4-RD. We further compared lymphadenopathy in patients who developed other manifestations of IgG4-RD (RD + , n=20, 36%) versus those who did not (RD - , n=35, 64%). We found that there were only minor significant differences between 2 groups, including frequency of receiving treatment (RD + , 90% vs. RD - , 60%, P =0.021) and higher serum levels of C-reactive protein (>8 mg/L, RD + , 53% vs. RD - , 13%, P =0.007). Other differences were either borderline or not significant, including mean age (RD + , 59.8 y vs. RD - , 51.9 y, P =0.097), male-to-female ratio (RD + , 16:4 vs. RD - , 28:7, P =1), constitutional symptoms (RD + , 25% vs. RD - , 9%, P =0.096), multiple enlarged lymph nodes (RD + , 45% vs. RD - , 26%, P =0.143), good response to therapy (RD + , 94% vs. RD - , 94%, P =1); higher serum IgG4 levels (>280 mg/dL, RD + , 75% vs. RD - , 51%, P =0.086), anemia (RD + , 45% vs. RD - , 43%, P =0.877), leukopenia (RD + , 0% vs. RD - , 3%, P =0.446), thrombocytopenia (RD + , 10% vs. RD - , 6%, P =0.556), positivity for antinuclear antibody (RD + , 24% vs. RD - , 29%, P =0.688), elevated serum levels of lactate dehydrogenase (>225 U/L, RD + , 0% vs. RD - , 20%, P =0.064), elevated serum IgE level (>100 IU/mL, RD + , 75% vs. RD - , 92%, P =0.238), and hypergammaglobulinemia (RD + , 90% vs. RD - , 86%, P =0.754). There were also no differences in morphologic patterns ( P =0.466), IgG4 + cell location ( P =0.104), eosinophil counts (RD + , 10.3±11.3 vs. RD - , 13.4±17.5, P =0.496), Epstein-Barr virus positivity (RD + , 35% vs. RD - , 60%, P =0.074), and Epstein-Barr virus-positive cell location ( P =0.351). Our findings suggest that there are minimal differences between stringently defined IgG4-RD lymphadenopathy with versus without other manifestations of IgG4-RD. These findings also suggest the existence of IgG4-RD lymphadenopathy as the sole presentation of IgG4-RD.

Differential IgG4-Producing Plasma Cell Infiltration in Non- and Post-Transplant Plasma Cell Hepatitis

Autoimmune hepatitis (AIH), post-transplant recurrent AIH (rAIH), and plasma cell-rich rejection (PCR) are clinical diagnoses with the shared histopathologic hallmark of plasma cell hepatitis (PCH). As these histologically and serologically indistinguishable diagnoses are differentiated by clinical context, it remains uncertain whether they represent distinct immunologic phenomena. Improved understanding of immunoglobulin subclass 4-producing plasma cells (IgG4-PC) has brought attention to IgG4 as an immunophenotypic biomarker. To date, degree and clinical significance of IgG4-PC infiltration in PCH remain elusive. This retrospective, single-center study assessed IgG4-PC infiltration in AIH, rAIH, and PCR via standardized immunohistochemistry analysis. Identified cases from 2005 to 2020 (n = 47) included AIH (treatment-naïve AIH (tnAIH): n = 15 and AIH-flare on treatment (fAIH); n = 10), rAIH (n = 8), and PCR (n = 14) were analyzed and correlated with clinical characteristics. IgG4-Positivity (# IgG4-PC/# pan-IgG-expressing cells) distribution was heterogenous and overlapping [tnAIH: 0.060 (IQR 0.040-0.079), fAIH: 0.000 (0.000-0.033), rAIH: 0.000 (0.000-0.035), PCR: 0.228 (0.039-0.558)]. IgG4-Positivity was inversely correlated with corticosteroid use (p < 0.001). IgG4-Positivity ≥0.500 was associated with rapid AST improvement (p = 0.03). The variable IgG4-Positivity of AIH, rAIH and PCR suggests diverse and overlapping immunopathologic mechanisms and that current diagnostic schemes inadequately capture PCH immunopathology. We propose incorporation of IgG4-Positivity to refine current PCH classification and treatment strategies.

Immunoglobulin G4-related Pleuritis Complicated with Minimal Change Disease

A 70-year-old woman with bilateral pleural effusion and respiratory failure was admitted to our hospital. Nephrotic syndrome due to minimal change disease had been diagnosed four months before admission. Because blood tests and a pleural fluid analysis did not reveal the etiology of her condition, we performed a video-assisted thoracoscopic pleural biopsy. No specific thoracoscopic findings were noted. The pathological findings revealed an increase in immunoglobulin G4 (IgG4)-positive cells; IgG4-related pleuritis was diagnosed. Her pleuritis improved with oral corticosteroid therapy. A further investigation was performed on previous kidney samples; however, the etiology of the nephrotic syndrome was not IgG4-related disease but minimal change disease.

The Role of IgG4 in Autoimmunity and Rheumatic Diseases

The distinguishing of the IgG4-related disease (IgG4-RD) from among other rheumatic diseases has brought attention to the IgG4 subclass of immunoglobulins. It is the least numerous subclass among immunoglobulins G. In general, IgG4 is considered to be non-inflammatory and tolerance inducing, due to its unique structure. However, in IgG4-RD this antibody plays a pathogenic role in activation of the fibrinogenesis and of the inflammatory process; there are also suggestions that it may be a marker of an abnormal inflammatory response. The importance of IgG4 for the pathogenesis of allergic diseases, with a vital role of its ratio to immunoglobulin E (IgE/IgG4 ratio), has been known for years. The role of IgG4 in the course and pathogenesis of rheumatic diseases is still being researched and is not yet fully understood. Increased IgG4 levels have been revealed in rheumatoid arthritis, although no clear link between this phenomenon and disease activity has been demonstrated. There are articles on the potential importance of IgG4 concentration (of both elevated and decreased serum levels) in Sjogren’s syndrome. Additionally, anti-nuclear IgG4 antibody significant titers have been detected in SLE patients, and it has been suggested that the effect of these antibodies on complement consumption and the production of proinflammatory cytokines may play a role in inhibiting the progression of SLE. IgG4 plays a role in autoimmune diseases other than rheumatic diseases, such as pemphigus, bullous pemphigoid, idiopathic membranous glomerulonephritis, or myasthenia gravis, but also in helmints infections. Research shows the importance of IgG4 in malignancy of neoplasms. Melanoma cells are known to stimulate IgG4 production through a modified Th2-based inflammatory response. The role of this immunoglobulin in cholangiocarcinoma is also considered as possible. The aim of this review article is to discuss the current knowledge of IgG4 not only from the perspective of the IgG4-RD but also from a point of view of other autoimmune diseases with particular emphasis on rheumatic diseases.

Immunoglobulin G4-related lymph node disease with an orbital mass mimicking Castleman disease: A case report

BACKGROUND

Immunoglobulin (Ig) G4-associated diseases are a group of systemic diseases involving multiple organs and are also known as IgG4-associated sclerosing diseases. IgG4-associated lymphadenopathy occurring in the lymph nodes is characterized by a lack of specificity due to its clinicopathological characteristics and must be differentiated from a variety of lesions, such as Castleman disease, lymphatic follicular reactive hyperplasia, and lymphoma.

CASE SUMMARY

A 65-year-old male patient, with Guillain-Barre syndrome for 5 years, presented to our hospital complaining of bilateral orbital mass for 2 years. After hospitalization, the results of the patient’s laboratory tests showed that immunoglobulin subgroup IgG4 was 33.90 g/L and IgG was 30.30 g/L, but serum interleukin-6 was normal. The pathological morphology of orbital mass and cervical lymph node were consistent, which showed that a large number of plasma cells and eosinophils were observed in the lymphatic follicles, and the interstitial fibrous tissue was proliferative. Immunohistochemistry showed that CD20 (B cells) (+), CD3 (T cells) (+), CD38 (+), IgG (+), IgG4 positive cells > 100/high powered field, and IgG4/IgG > 40%. Combined with clinical and immunohistochemical results, lymphadenopathy was consistent with Castleman disease-like IgG4-associated sclerosing disease. Prednisone acetate treatment was given at 40 mg/d. After 2 wk, the superficial lymph nodes and orbital masses shrank, and the IgG4 level decreased. As prednisone acetate was regularly used at a reduced dosage, no recurrence of the disease has been observed.

CONCLUSION

This case suggested that it is necessary to proceed cautiously in clinical practice with such patients, and immunoglobulin, complement, interleukin-6, C-reactive protein, and other examinations should be performed to confirm the diagnosis.

Fc receptors gone wrong: A comprehensive review of their roles in autoimmune and inflammatory diseases

Systemic autoimmune and inflammatory diseases have a complex and only partially known pathophysiology with various abnormalities involving all the components of the immune system. Among these components, antibodies, and especially autoantibodies are key elements contributing to autoimmunity. The interaction of antibody fragment crystallisable (Fc) and several distinct receptors, namely Fc receptors (FcRs), have gained much attention during the recent years, with possible major therapeutic perspectives for the future. The aim of this review is to comprehensively describe the known roles for FcRs (activating and inhibitory FcγRs, neonatal FcR [FcRn], FcαRI, FcεRs, Ro52/tripartite motif containing 21 [Ro52/TRIM21], FcδR, and the novel Fc receptor-like [FcRL] family) in systemic autoimmune and inflammatory disorders, namely rheumatoid arthritis, Sjögren's syndrome, systemic lupus erythematosus, systemic sclerosis, idiopathic inflammatory myopathies, mixed connective tissue disease, Crohn's disease, ulcerative colitis, immunoglobulin (Ig) A vasculitis, Behçet's disease, Kawasaki disease, IgG4-related disease, immune thrombocytopenia, autoimmune hemolytic anemia, antiphospholipid syndrome and heparin-induced thrombocytopenia.

The Role of PD-1/PD-Ls in the Pathogenesis of IgG4-RD

OBJECTIVE

To investigate the role of Programmed cell death protein 1 (PD-1) and its two ligands PD-L1 and PD-L2 in the pathogenesis of IgG4-RD.

METHODS

Patients with IgG4-RD (n = 43) as well as healthy controls (n = 34) were recruited. Expression levels of PD-1, PD-L1 and PD-L2 in plasma, submandibular gland and T cell subsets were determined by ELISA, immunohistochemistry and flow cytometry. Naive T cells were stimulated with or without PD-L1/PD-L2 or anti-PD-L1/anti-PD-L2 for 7 days and the proportion of CD4+CD25+Treg cells was detected by flow cytometry.

RESULTS

The expression of PD-1, PD-L1 and PD-L2 in the plasma, submandibular gland and on the surface of Treg cells were increased in IgG4-RD patients. Plasma sPD-1 was positively correlated with serum IgG, IgG1, IgG3, IgG4, IgG4-RD RI and numbers of organs involved, and negatively correlated with serum IgM, IgA, C3 and C4. Plasma sPD-L2 was positively correlated with serum IgG1, plasma sPD-L1 was positively correlated with sPD-L2 and negatively correlated with C3. Stimulation of PD-L1 but not PD-L2 promoted the differentiation of naive T cells from IgG4-RD patients into CD4+CD25+Treg cells.

CONCLUSION

Plasma concentration of sPD-1, sPD-L1 and sPD-L2 were significantly increased in patients with IgG4-RD, and the expression of PD-1 and PD-L2 on Treg cells were upregulated. PD-1/PD-L1 can promote the differentiation of naive T cells into Treg cells and thus participate in the pathogenesis of IgG4-RD.

The enigmatic immunoglobulin G4-related disease and its varied cardiovascular manifestations

Immunoglobulin G4-related disease (IgG4-RD) is a systemic fibroinflammatory disease characterised by multiorgan lymphoplasmacytic infiltration, obliterative phlebitis and storiform fibrosis. It can be associated with cardiovascular pathology. The objective of this narrative review is to summarise the published literature on cardiovascular manifestations of IgG4-RD and to provide a basis for diagnosis and management of the condition by the practising cardiologist.We propose the following categorisations of cardiovascular IgG4-RD: aortitis, medium-vessel arteritis, pulmonary vascular disease, phlebitis, valvulopathy, pericarditis, myocardial disease and antineutrophilic cytoplasmic antibody-associated vasculitis. We also review herein developments in radiological diagnosis and reported medical and surgical therapies. Cardiovascular lesions frequently require procedural and/or surgical interventions, such as aortic aneurysm repair and valve replacement. IgG4-RD of the cardiovascular system results in serious complications that can be missed if not evaluated aggressively. These are likely underdiagnosed, as clinical presentations frequently mimic cardiovascular disease due to more common aetiologies (myocardial infarction, abdominal aortic aneurysm and so on). While systemic corticosteroids are the mainstay of IgG4-RD treatment, biological and disease-modifying agents are becoming more widely used. Cardiologists should be aware of cardiovascular IgG4-RD as a differential diagnosis, and understand the roles of corticosteroids, disease-modifying agents and biologicals, as well as their integration with surgical approaches. There are several knowledge gaps, including diagnosis, risk factors, pathogenesis and appropriate management in Ig4-RD of the cardiovascular system. Areas lacking well-conducted randomized trials include safety of steroids in the setting of vascular aneurysms and the role of disease-modifying drugs and biological agents in patients with established cardiovascular complications of this multifaceted enigmatic disease.

IgG4-related pleural disease in a patient with pulmonary adenocarcinoma under durvalumab treatment: a case report

Background

Immune checkpoint inhibitors (ICIs) are the standard treatment for non-small cell lung cancer. The unique adverse events that can arise after treatment with ICIs are known as immune-related adverse events (irAE). As the number of cases under treatment with ICIs increases, new types of characteristics of irAE have emerged. This case report suggests that IgG4-related pleural disease could occur as an irAE.

Case presentation

A 64-year-old man was diagnosed with pulmonary adenocarcinoma stage IIIB. Following concurrent chemoradiotherapy, durvalumab was administered every two weeks. The patient complained of dyspnea on effort 4 months after the initiation of durvalumab therapy. Chest CT scans showed mild bilateral pleural effusion 4 months after the initiation of durvalumab therapy, and the amount of pleural effusion increased further at 7 months. Durvalumab was thought to be a potential cause of pleural effusion and was withdrawn after 13 courses of administration over 7 months. The level of serum IgG4 was 2750 mg/dL. The levels of IgG4 of the pleural fluids were 2790 mg/dL on the right side and 2890 mg/dL on the left side at 7 months. Microscopic examination of the pleural biopsy revealed lymphoplasmacytic infiltration with storiform fibrosis. Immunohistochemical examinations showed that the number of IgG4-positive cells was > 20/high power field and the percentage of IgG4-positive to IgG-positive plasma cells was > 50%. Oral prednisolone at a dose of 30 mg/day was initiated, and remarkable clinical improvements were achieved. After 4 months of prednisolone therapy, the level of serum IgG4 decreased to 370 mg/dL and chest CT revealed the disappearance of bilateral pleural effusion.

Conclusion

This was a case of IgG4-related pleural disease in a patient with pulmonary adenocarcinoma under durvalumab treatment. To our knowledge, this is the first case report of IgG4-related pleural disease as an irAE. It is important to consider the possibility of IgG4-related pleural disease in cases of pleural effusion during the treatment with ICIs.

Review of a novel disease entity, immunoglobulin G4-related disease

Immunoglobulin G4 (IgG4)-related dacryoadenitis and sialoadenitis (IgG4-DS) are part of a multiorgan fibroinflammatory condition of unknown etiology termed IgG4-related disease (IgG4-RD), which has been recognized as a single diagnostic entity for less than 15 years. Histopathologic examination is critical for diagnosis of IgG4-RD. CD4+ T and B cells, including IgG4-expressing plasma cells, constitute the major inflammatory cell populations in IgG4-RD and are thought to cause organ damage and tissue fibrosis. Patients with IgG4-RD who have active, untreated disease exhibit significant increase of IgG4-secreting plasmablasts in the blood. Considerable insight into the immunologic mechanisms of IgG4-RD has been achieved in the last decade using novel molecular biology approaches, including next-generation and single-cell RNA sequencing. Exploring the interactions between CD4+ T cells and B lineage cells is critical for understanding the pathophysiology of IgG4-RD. Establishment of pathogenic T cell clones and identification of antigens specific to these clones constitutes the first steps in determining the pathogenesis of the disease. Herein, the clinical features and mechanistic insights regarding pathogenesis of IgG4-RD were reviewed.

Tissue-infiltrating immune cells contribute to understanding the pathogenesis of Kimura disease: A case report

RATIONALE

Kimura disease (KD) is a rare, chronic inflammatory disorder characterized by subcutaneous granuloma in the head and neck region, as well as increased eosinophil counts and high serum immunoglobulin E (IgE) levels. Kimura disease is suspected to be an IgE-mediated disease, associated with an allergic response, in which antigen-specific B cells are stimulated to undergo specific IgE class switching with disease-specific CD4+ T (Th) cells help. Thus, exploration of the Th cells in affected tissues with KD is a highly promising field of the investigation. However, there have been no reports with direct evidence to implicate Th cells in affected lesions with KD. Here we quantitatively demonstrate that CD4+ GATA3+ T cells and interleukin (IL)-4+ IgE+ c-kit+ mast cells prominently infiltrate in affected lesion with KD.

PATIENT CONCERNS

A 56-year-old Japanese man who exhibited painless swelling in the left parotid region.

DIAGNOSES

Diagnosis of KD was made based on characteristic histopathologic findings, in conjunction with peripheral eosinophilia and elevated serum IgE levels.

INTERVENTIONS

The patient underwent corticosteroid therapy and had been followed for 2 years.

OUTCOMES

We report a rare case of KD of the parotid region in a 56-year-old man, followed by corticosteroid therapy for 2 years. The mass decreased in size and skin itchiness decreased after therapy. He was discharged without any complications. Furthermore, we quantitatively demonstrate the dominance of CD4+ GATA3+ T cells in affected tissues of KD and detect IL-4+ IgE+ c-kit+ mast cells in lesions by multicolor staining approaches.

LESSONS

The findings from this case suggest that peripheral blood eosinophilia might serve as a marker of recurrent disease, long-term follow-up is necessary due to the possibility of recurrent. Interactions among expanded IgE+ B cells, CD4+ GATA3+ T cells, eosinophils, and activated mast cells might play a critical role in the pathogenesis of KD.

The potential role of follicular helper T cells in idiopathic multicentric Castleman disease with and without TAFRO syndrome

Idiopathic multicentric Castleman disease (iMCD) is a systemic inflammatory disease of unknown etiology caused by hypercytokinemia. Recently, TAFRO (thrombocytopenia, anasarca, fever, renal failure or reticulin fibrosis, and organomegaly) syndrome has been reported, which shows similar histopathological findings to iMCD and factors associated with a poor prognosis. iMCD shows no plasma cell infiltration in the germinal center (GC), but CD38-positive (CD38+)-plasma cells are observed in the interfollicular area. Our previous report revealed that atrophic change of GC, glomeruloid vascular proliferation, and abnormal proliferation of follicular dendritic cells are more prominent in iMCD with TAFRO (TAFRO+) in comparison to iMCD without TAFRO (TAFRO-). In addition, the numbers of CD38+ and immunoglobulin G4-positive (IgG4+) plasma cells were decreased in the interfollicular area. The roles of T follicular helper cells (Tfh) are well-known to assist B-cell proliferation, maturation, and differentiation．It maintains the formation of GC and is also related in the class switching of IgG isotypes, including IgG4. Thus, we immunohistochemically examined the number of Tfh in GCs in both TAFRO- and TAFRO+ iMCD. The number of Tfh was significantly decreased in TAFRO- iMCD (n = 9) and was further decreased in TAFRO+ iMCD (n = 18) in comparison to non-specific lymphadenopathy (n = 6) and IgG4-related disease (n = 4). These results suggest that decreased Tfh may be one etiology of iMCD.