IgG4-Related Disease: Mimickers and Diagnostic Pitfalls

Immune Profile Differences between IgG4-Related Diseases and Primary Sjögren's Syndrome

Purpose

Immunoglobulin G4-related disease (IgG4-RD) share clinical features with primary Sjögren's syndrome (pSS). This study aimed to identify altered serological parameters and potential biomarkers of IgG4-RD and pSS.

Methods

Forty IgG4-RD patients, 40 pSS patients, and 40 healthy controls (HC) were enrolled in this study. Routine serological parameters and clinical manifestations were assessed. IgG subclasses (IgGSc) were detected using a Siemens BN P, and lymphocyte subsets were analyzed using flow cytometry. Cytokines assays were performed using cytometric bead array.

Results

Compared to pSS, IgG4-RD patients had higher IgG4 (p <0.001) and lower IgG1 (p =0.014). The natural killer (NK) cells (p = 0.004), CD4+ T cells (p = 0.028), and TBNK cells (p = 0.040) were increased in IgG4-RD compared to pSS. IgG4 used to differentiate IgG4-RD from pSS produced an area under the curve (AUC) of up to 0.952. In addition, we compared serum parameters, immune cells, and cytokines of IgG4-RDwith mouth dryness or eye dryness with those of pSS with the same symptoms, and similar serological changes were observed. IgG4-RD patients with mouth dryness had higher IgG4 (p <0.001) and Th cells (p = 0.016) but lower IgG1 (p = 0.009) compared to pSS with dry mouth. IgG4-RD patients with eye dryness had higher levels of IgG4 (p <0.001), Treg cells (p = 0.037), and NK cells (p = 0.017) than pSS patients with eye dryness. Moreover, IgG4-RD patients with mouth and eye dryness had higher levels of B (p = 0.006), Th (p = 0.026), Th2 (p = 0.007), and Treg cells (p = 0.028) than IgG4-RD patients without mouth and eye dryness.

Conclusion

Immune system disorder is an outstanding feature of IgG4-RD, and its feature differ from pSS. Assessment of immune status is important in the diagnosis and differential diagnosis of IgG4-RD.

Navigating the labyrinth: Phenotypes of IgG4-related disease

ABSTRACT

We report a case of an elderly female with subacute submental neck swelling, dry cough, and a history of significant weight loss. Unexpectedly, a left submandibular chronic sialadenitis was noted on ultrasound of the neck, along with a thyroid nodule that, on biopsy, showed lymphocytic infiltration. High-resolution computed tomography of the lungs revealed multifocal irregular consolidations with lymphadenopathy, and possible infective causes, including tuberculosis, were ruled out after a thorough microbiological evaluation. It was only after a positron emission tomography-guided lung biopsy with specialized immunohistochemical staining was performed that the diagnosis of IgG4-related disease (IgG4-RD) was confirmed. Our patient exhibited overlapping features of head and neck-limited and Mikulicz/systemic phenotype of IgG4. In this case report, we highlight the clinical phenotypes of IgG4-RD, their respective differential diagnoses, and discuss our approach to this challenging case.

Malignancy and mass-forming phenotypes of IgG4-related disease: a challenging diagnosis

Mass-forming phenotypes of IgG4-related disease (IgG4-RD) mimic malignancy and histological confirmation can be challenging. A woman in her 70s with HIV infection presented with painless obstructive jaundice and weight loss. Magnetic resonance imaging was suggestive of unresectable cholangiocarcinoma. Tumour markers and serum IgG4 were normal. Percutaneous liver biopsy was consistent with IgG4-RD inflammatory pseudotumour, with complete response to glucocorticoid therapy. Two years later, a new episode of obstructive jaundice occurred, with CT showing a solid lesion in the head of the pancreas with double duct sign and encasement of the portal vein. Re-induction therapy was tried without response. Fine-needle biopsy was consistent with pancreatic cancer. Supportive care was offered and the patient died 8 months later, with no signs of disease progression on subsequent imaging. We discuss the challenges of IgG4-RD diagnosis and treatment and the differential diagnosis between mass-forming phenotypes and malignancy, highlighting the difficulties in managing such patients.

Myelodysplastic syndrome with IgG4‑related disease: A case report

At present, to the best of our knowledge, there are only a few case reports of IgG4-related disease (IgG4-RD) involving myelodysplastic syndrome (MDS), yet the incidence of MDS and IgG4-RD is increasing in middle-aged and elderly people. The present study presents a case of MDS combined with IgG4-RD admitted to Zhejiang Provincial Hospital of Chinese Medicine in September 2022. The (66-year-old; male) patient was admitted to the hospital due to hematopenia with an elevated IgG4 index. The diagnosis of MDS combined with IgG4-RD was confirmed after various exams, including pathological examination. The condition of the patient improved after 3 weeks of hormone therapy, with a significant increase in complete blood count compared with the pre-treatment period. MDS is a malignant hematological disorder with a high risk of conversion to leukemia, and IgG4-RD is a systemic immune-mediated disease with a poor prognosis often associated with malignancy. The present study presents and reviews the literature to better understand the coexistence of these two diseases.

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.

Unicentric Castleman Disease: Illustration of Its Morphologic Spectrum and Review of the Differential Diagnosis

CONTEXT.—

Unicentric Castleman disease (UCD) is a dynamic entity with a wide spectrum of morphologic findings. UCD can be further subdivided into hyaline-vascular and mixed/plasmacytic variants. Hyaline-vascular UCD has both follicular and interfollicular (stromal) changes, and occasionally these lesions show a skewed representation of either the follicular or stromal compartments. Plasmacytosis is usually minimal in the hyaline-vascular variant. The mixed/plasmacytic variant of UCD is composed of sheets of plasma cells often associated with a variable number of follicles with regressive changes.

OBJECTIVE.—

To illustrate the differential diagnosis of UCD, as it is quite broad and includes lymphomas, plasma cell neoplasms, stromal neoplasms such as follicular dendritic cell sarcoma and vascular neoplasms, immunoglobulin G4-related disease, infections, and other rare lesions. An additional objective is to enhance awareness of the morphologic features of UCD in excisional and in small core-needle biopsy specimens, the latter of which may inadvertently target follicle- or stroma-rich areas, causing diagnostic challenges.

DATA SOURCES.—

In this review, we provide readers a concise illustration of the morphologic spectrum of UCD that we have encountered in our practice and a brief discussion of entities in the differential diagnosis.

CONCLUSIONS.—

UCD exhibits a broad spectrum of morphologic changes, and awareness of these morphologic variations is key to avoid misdiagnosis.

IgG4-related disease presenting as severely symptomatic hypercalcemia: A case report and review of literature

Immunoglobulin G4-related disease (IgG4-RD)-associated hypercalcemia has rarely been reported. We report a case of IgG4-RD that presented as severe symptomatic hypercalcemia. A 50-year-old woman with a history of sustained bilateral periorbital swelling and proptosis for more than 5 years presented to our hospital complaining of a 3-day history of significant and progressive nausea, vomiting, loss of appetite, fatigue, and pruritus. She denied a long history of medication. On admission, laboratory tests showed severe hypercalcemia with serum adjusted calcium elevated to 4.34 mmol/L and renal dysfunction with serum creatinine elevated to 206 μmol/L. Urinary calcium excretion was increased. The serum IgG4 subclass was markedly elevated to 22.4 g/L with polyclonal hypergammaglobulinemia. Tests of autoantibodies were all negative. Bone metabolism markers that reflect the activity of osteoblasts and osteoclasts were all significantly elevated. However, the levels of intact parathyroid hormone and 25(OH) vitamin D3 were decreased. B-ultrasonography showed chronic inflammation of bilateral submandibular glands. Neither bone marrow biopsy nor positron emission tomography - computed tomography examination showed evidence of neoplastic diseases. The patient was treated with intravenous saline infusion, loop diuretics, salmon calcitonin, glucocorticoids, and hemodialysis with a good response.

A Rare Case of Orbital Castleman Disease with Overlapping IgG4-Related Disease

Multicentric Castleman disease (MCD) is a systemic lymphoproliferative disorder that can lead to mass lesions in various body parts, including the lungs, kidneys, and extranodal sites. Meanwhile, orbital Castleman disease is extremely rare. Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized fibroinflammatory disorder and is characterized by the formation of tumor-like lesions with lymphoplasmacytic infiltrates, which are enriched in IgG4-positive plasma cells and may present with a characteristic storiform pattern of fibrosis to variable degrees. In this study, we report a case of a 67-year-old Taiwanese man with a 7-year history of bilateral eyelid swelling and proptosis. Orbital magnetic resonance imaging revealed soft tissue lesions in the bilateral intraconal region, demonstrating strong enhancement in the lacrimal glands, and extension into the bilateral infraorbital foramen, suggesting an orbital lymphoproliferative disease. The histopathological results of the intraorbital tumor excision were suggestive of a plasma-cell-predominant mixed-cell variant of MCD. However, the patient also showed definitive signs of IgG4-RD, including lacrimal gland enlargement and histopathological results of plasmacytosis, fibrosis, and germinal centers, with an increased ratio of IgG4 cells and elevated serum IgG4 levels. This case suggests a potential interacting pathway between these two disease entities that needs further studies.

Pancreatic cancer, autoimmune or chronic pancreatitis, beyond tissue diagnosis: Collateral imaging and clinical characteristics may differentiate them

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies and is developing into the 2nd leading cause of cancer-related death. Often, the clinical and radiological presentation of PDAC may be mirrored by other inflammatory pancreatic masses, such as autoimmune pancreatitis (AIP) and mass-forming chronic pancreatitis (MFCP), making its diagnosis challenging. Differentiating AIP and MFCP from PDAC is vital due to significant therapeutic and prognostic implications. Current diagnostic criteria and tools allow the precise differentiation of benign from malignant masses; however, the diagnostic accuracy is imperfect. Major pancreatic resections have been performed in AIP cases under initial suspicion of PDAC after a diagnostic approach failed to provide an accurate diagnosis. It is not unusual that after a thorough diagnostic evaluation, the clinician is confronted with a pancreatic mass with uncertain diagnosis. In those cases, a re-evaluation must be entertained, preferably by an experienced multispecialty team including radiologists, pathologists, gastroenterologists, and surgeons, looking for disease-specific clinical, imaging, and histological hallmarks or collateral evidence that could favor a specific diagnosis. Our aim is to describe current diagnostic limitations that hinder our ability to reach an accurate diagnosis among AIP, PDAC, and MFCP and to highlight those disease-specific clinical, radiological, serological, and histological characteristics that could support the presence of any of these three disorders when facing a pancreatic mass with uncertain diagnosis after an initial diagnostic approach has been unsuccessful.

Tear levels of IL-7, IL-1α, and IL-1β may differentiate between IgG4-related disease and Sjögren's syndrome

We aim to assess and compare a cytokine and chemokine profile in tears from patients with IgG4-related disease (IgG4-RD) and Sjögren's syndrome (SS), and to see if this profile could aid in differentiating these two diseases. We included 10 patients with IgG4-RD who met the Comprehensive Diagnostic Criteria for IgG4-RD and 17 patients who met the AECG criteria for primary SS. The Schirmer-I test was carried out using two standardized sterile tear strips, which were then immediately frozen at - 86 °C until assayed. The tears were extracted from the strips after they had been defrosted using a buffer containing 0.5 M NaCl and 0.5% Tween-20. The amounts (pg/ml) of the following cytokines and chemokines were then measured using luminometry: IFN-γ, TNF-α, G-CSF, IL-1-α, IL-1β, IL-4, IL-7, IL-12p40, IL-12p70, IL-13, IL-17A, CCL2, CCL3, CCL4, CCL11, and CXCL10. In the IgG4-RD group, seven patients had lacrimal gland involvement, five had dry eye symptoms, and six had a positive Schirmer-I test. In the SS group, 16 (94.1%) had dry eyes and all had a positive Schirmer-I test. We were able to differentiate between both diseases using levels of IL-7, IL-1α, and IL-1β; in particular, the IL-7/IL-1α and IL-7/IL-1β ratios had the best discriminatory potential, with cut-off values of 0.32 (AUC: 0.93, sensitivity: 94%, specificity: 80%, p = 0.0003) and 12.55 (AUC: 0.96, sensitivity: 94%, specificity: 90%, p = 0.0001), respectively. Our results suggest that IL-7, IL-1α, and IL-1β tear levels could help differentiate IgG4-RD from SS. Key Points • The lacrimal gland is frequently involved in IgG4-RD and SS. This characteristic makes both diseases mimics of one another. • Patients with IgG4-RD and SS have different profiles of tear cytokines and chemokines. • Tear IL-7, IL-1α, and IL-1β levels may serve as helpful biomarkers in separating IgG4-RD from SS.

Memory CD4+T cell profile is associated with unfavorable prognosis in IgG4-related disease: Risk stratification by machine-learning

IgG4-related disease (IgG4-RD) is a chronic immune-mediated disease with heterogeneity. In this study, we used machine-learning approaches to characterize the immune cell profiles and to identify the heterogeneity of IgG4-RD. The XGBoost model discriminated IgG4-RD from HCs with an area under the receiver operating characteristic curve of 0.963 in the testing set. There were two clusters of IgG4-RD by k-means clustering of immunological profiles. Cluster 1 featured higher proportions of memory CD4⁺T cell and were at higher risk of unfavorable prognosis in the follow-up, while cluster 2 featured higher proportions of naïve CD4⁺T cell. In the multivariate logistic regression, cluster 2 was shown to be a protective factor (OR 0.30, 95% CI 0.10-0.91, P = 0.011). Therefore, peripheral immunophenotyping might potentially stratify patients with IgG4-RD and predict those patients with a higher risk of relapse at early time.

Serum biomarkers for the differentiation of autoimmune pancreatitis from pancreatic ductal adenocarcinoma

Autoimmune pancreatitis (AIP), a chronic inflammation caused by the immune system attacking the pancreas, usually presents imaging and clinical features that overlap with those of pancreatic ductal adenocarcinoma (PDAC). Serum biomarkers, substances that quantitatively change in sera during disease development, are a promising non-invasive tool with high utility for differentiating between these diseases. In this way, the presence of AIP is currently suspected when serum concentrations of immunoglobulin G4 (IgG4) antibody are elevated. However, this approach has some drawbacks. Notably, IgG4 antibody concentrations are also elevated in sera from some patients with PDAC. This review focuses on the most recent and relevant serum biomarkers proposed to differentiate between AIP and PDAC, evaluating the usefulness of immunoglobulins, autoantibodies, chemokines, and cytokines. The proposed serum biomarkers have proven useful, although most studies had a small sample size, did not examine their presence in patients with PDAC, or did not test them in humans. In addition, current evidence suggests that a single serum biomarker is unlikely to accurately differentiate these diseases and that a set of biomarkers will be needed to achieve adequate specificity and sensitivity, either alone or in combination with clinical data and/or radiological images.

Clinical Characteristics and Classification Criteria Performance in a Single-Center Cohort of 114 Patients With Immunoglobulin G4-Related Disease

INTRODUCTION/OBJECTIVES

Immunoglobulin G4-related disease (IgG4-RD) is a heterogeneous fibroinflammatory condition. The 2019 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) Classification Criteria for IgG4-RD were published to provide unified classification criteria in clinical research. The purpose of this study was to characterize demographics, disease manifestations, and treatments of patients with IgG4-RD and assess performance of the Classification Criteria in a heterogeneous cohort with a large population of Black patients.

METHODS

This was a medical records review of all patients referred to a specialized IgG4-RD clinic. Demographics, serology, histopathology, disease manifestations, and treatment information were collected and analyzed. An ACR/EULAR Classification Criteria score for IgG4-RD was calculated to compare performance in definite diagnosis, probable diagnosis, and mimicker groups.

RESULTS

A total of 198 patients were evaluated. Eighty-five (43%) were mimickers. Of the remaining 114, 58 (51%) were classified as definite, and 56 (49%) as probable cases by treating clinicians. Pancreatitis was the most common presentation (37%) among 28 different organ manifestations of IgG4-RD. In patients with definite clinical diagnosis of IgG4-RD, 84% met the IgG4-RD Classification Criteria (i.e., score ≥20) with mean score of 29. Only 9% of the probable cases met this threshold with an average score of 8. None of the mimickers met the Classification Criteria.

CONCLUSIONS

This study highlights the broad spectrum of IgG4-RD and validates the use of the ACR/EULAR Classification Criteria for IgG4-RD, including a large proportion of Black patients. As shown in this study, IgG4-RD is a heterogeneous disease and continues to represent a diagnostic challenge to clinicians.

Diagnosis of inflammatory bowel disease according to human IgG4 and possibilities of evaluating efficacy of the therapy

Taking into account the progress of understanding diagnosis, course prognosis, evaluation of effectiveness of therapy of inflammatory bowel disease and also differentiation diagnosis between its main forms – ulcerative colitis and Crohn’s disease, the search for efficient non-invasive markers for solving those issues is extremely relevant. The patients were divided into groups depending on nosology and severity of the course of the disease. All the patients had undergone endoscopic study for diagnosis verification and biopsy samples were taken for further detection of tissue IgG4 using the immunohistochemical method. Also, we determined concentration of serum IgG4. Increase in IgG4content in blood serum was determined in 54.0% of the cases of inflammatory bowel disease. Concentration of IgG4 in patients suffering ulcerative colitis was higher (by 2.31 and 2.46 times) compared with its level in the control group and patients with Crohn’s disease, respectively. We found relationships between the concentration of serum IgG4 and the activity of the disease. In patients with ulcerative colitis, increased tissue IgG4 was found more often than in patients with Crohn’s disease (by 2.77 times, Р < 0.05). We determined the relationship between tissue IgG4 and histological activity. Simultaneous increase in serum IgG4 and presence of tissue IgG4 during ulcerative colitis were more frequent than during Crohn’s disease (by 2.66 times). In all examined groups of patients, we determined decrease in serum IgG4 content (by 1.66 times) after treatment. Concentration of serum IgG4 and positive tissue IgG4 in ulcerative colitis patients exceeded such in Crohn’s disease patients, which may be used for differentiation diagnosis between those disease types. We determined dependence of IgG4 concentration on severity and duration of the disease, which could be used as a prognostic marker. Decrease in IgG4 content in blood serum against the background of the therapy shows that this indicator could be used as a marker of treatment efficacy. Perspectives of further studies are as follows: parameters of concentration of serum IgG4 and presence of tissue IgG4 could be used as diagnostic and prognostic biomarkers and be introduced to practice for differentiation diagnosis between ulcerative colitis and Crohn’s disease, and could be used as prognostic marker of severity of the disease and therapy efficacy.

Laboratory characteristics of IgG4-related disease: A retrospective study from a single tertiary medical center

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated fibroinflammatory condition with unique histopathological features that can affect most organs, making diagnosis challenging. This study characterized detailed laboratory characteristics of IgG4-RD. Baseline clinical and laboratory features of 33 patients with IgG4-RD were reviewed, including serum IgG4 concentrations, serum free light chains (sFLCs), IgGĸ- and IgGλ-heavy/light chains (HLCs), capillary serum protein electrophoresis (SPE), and immunofixation electrophoresis (IFE) of IgG4 subclass. The cohort of 33 patients showed male predominance (94%), with 8 (24%) exhibiting multiple organ involvement. Most patients (88%) had an elevated IgG4 concentration, and 67% had elevated erythrocyte sedimentation rate and IgE levels. Median IgG4 concentration at baseline was significantly higher in patients with >2 organs involved than those with ≤2. Furthermore, erythrocyte sedimentation rate was significantly correlated with serum IgG4 concentrations at baseline. SPE results demonstrated polyclonal gammopathy in most patients. Half of the patients had an increased κ/λ sFLC ratio, 42% had an increased IgGκ/IgGλ HLC ratio. Most patients exhibited hypergammaglobulinemia in the anodal end of the ɤ region on SPE. This study describes detailed laboratory features of IgG4-RD. Although none of these tests are considered diagnostically sufficient by itself, the provided laboratory characteristics can increase awareness of this disorder and help distinguish it from other IgG4-RD mimics.

Idiopathic multicentric Castleman disease and associated autoimmune and autoinflammatory conditions: practical guidance for diagnosis

Idiopathic multicentric Castleman disease (iMCD) is an infrequent and life-threatening disorder characterised by systemic inflammatory symptoms, generalised lymphadenopathy, polyclonal lymphocyte proliferation, and organ dysfunction caused by a hyperinflammatory state. It accounts for one third to one half of all multicentric Castleman disease (MCD) cases. iMCD is often associated with autoimmune manifestations that may precede the iMCD diagnosis, be identified at the same time or follow it. In addition, iMCD may also coincide with a number of autoimmune diseases (such as psoriasis or myasthenia gravis) or autoinflammatory diseases (such as familial Mediterranean fever). Moreover, diverse inflammatory disorders, such as rheumatoid arthritis, systemic lupus erythematosus, adult-onset Still disease, systemic juvenile idiopathic arthritis, immunoglobulin (IgG4) related disease, or the recently described VEXAS syndrome, can present clinical features or lymphadenopathy with histopathological "Castleman-like" findings compatible with those of iMCD. Given the iMCD clinical heterogeneity and the overlap with other autoimmune or autoinflammatory disorders, iMCD diagnosis can be challenging. In this review, we explore the overlap between iMCD and inflammatory diseases and provide practical guidance on iMCD diagnosis in order to avoid misdiagnosis and confusion with other autoimmune or autoinflammatory conditions.

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.

IgG4-related disease. Clinical manifestation differential diagnosis and recent International Diagnostic Criteria for IgG4-related disease

Immunoglobulin G4- related disease (IgG4-RD) is a rare systemic fibro-inflammatory disorder. Autoimmune pancreatitis is the most frequent manifestation of IgG4-RD. However, IgG4-RD can affect any organ such as salivary glands, orbits, retroperitoneum, prostate and many others. Recent research enabled a clear clinical and histopathological description of IgG4-RD and in 2019 four Clinical phenotypes of IgG4-related disease were described. Diagnosis is based on morphological examination with typical findings of lymphoplasmocellular inflammation, storiform fibrosis and obliterative phlebitis in IgG4-RD biopsies and the tissue invading plasma cells largely produce IgG4. Elevated serum IgG4 levels are found in many but not all patients. New diagnostic criteria for IgG4-RD have been published recently in 2019 and 2021. This review summarizes current knowledge on pathophysiology, clinical manifestations, diagnosis and differential diagnosis of IgG4-RD from the point of view 2022 and in next article brings overview of the IgG4-RD therapy.