IgG4-Related Disease

Autoimmune MONDO:0017287 Pathograph 8 Show in embeddings browser Autoimmune Disease Fibroinflammatory Disease

A rare immune-mediated fibroinflammatory condition characterized by tumefactive lesions, a dense lymphoplasmacytic infiltrate rich in IgG4-positive plasma cells, storiform fibrosis, and often elevated serum IgG4 concentrations. The disease can affect virtually any organ but most commonly involves the pancreas (autoimmune pancreatitis), salivary and lacrimal glands, bile ducts, kidneys, retroperitoneum, and aorta. Left untreated, it leads to progressive fibrosis and organ damage.

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Subtypes

IgG4-Related Autoimmune Pancreatitis (Type 1 AIP)

The most common organ manifestation, presenting as diffuse or focal pancreatic enlargement with characteristic periductal lymphoplasmacytic infiltrate. Often presents with obstructive jaundice.

IgG4-Related Dacryoadenitis and Sialadenitis

Bilateral enlargement of lacrimal and/or salivary glands (historically called Mikulicz disease). Presents with painless symmetrical gland swelling.

◈

Mechanistic Hypotheses

Plasmablast-Autoantigen Fibrosis Driver Model

plasmablast_autoantigen_fibrosis_driver_model CANONICAL

A still-incomplete adaptive immune model in which unresolved autoantigen or innate triggers expand B-cell/plasmablast and T-cell axes; Tfh cells promote IgG4 class switching, plasmablasts mark and sustain the B-lineage response, and CD4-positive cytotoxic T cells provide fibrogenic cytokines that drive storiform fibrosis and organ injury.

Pathograph links

Candidate Autoantigen Recognition and Antigen Presentation -> Tfh-Mediated IgG4 Class Switching and Plasma Cell Differentiation INDIRECT UNKNOWN INTERMEDIATES Antigen-experienced B cells are inferred to recruit T-cell help that promotes plasmablast differentiation and IgG4 class switching.

Candidate Autoantigen Recognition and Antigen Presentation -> CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production INDIRECT UNKNOWN INTERMEDIATES Antigen-presenting B-lineage cells may sustain CD4+ cytotoxic T-cell expansion, but the dominant self-antigens and tissue-specific intermediates remain unresolved.

Tfh-Mediated IgG4 Class Switching and Plasma Cell Differentiation -> IgG4-Positive Plasmablast Expansion INDIRECT KNOWN INTERMEDIATES Tfh-driven B-cell help promotes plasmablast differentiation and IgG4 class switching in the canonical adaptive immune model.

IgG4-Positive Plasmablast Expansion -> IgG4-Positive Plasma Cell Infiltration INDIRECT KNOWN INTERMEDIATES Expanded IgG4-positive plasmablasts feed the antibody-secreting plasma-cell compartment that accumulates in affected tissues.

IgG4-Positive Plasmablast Expansion -> CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production INDIRECT UNKNOWN INTERMEDIATES Activated B cells and plasmablasts may collaborate with CD4+ CTLs, plausibly through antigen presentation, but the antigenic and tissue-specific intermediates remain unresolved.

CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production -> Storiform Fibrosis INDIRECT KNOWN INTERMEDIATES Profibrotic cytokine-secreting CD4+ CTLs provide an immune-cell mechanism for chronic inflammation and fibrosis.

Storiform Fibrosis -> Organ-Specific Fibroinflammatory Injury INDIRECT KNOWN INTERMEDIATES Persistent fibroblast and myofibroblast activation remodels affected organ tissue, with the clinical pattern shaped by organ-specific antigen, barrier, and injury contexts.

Deep research

OpenScientist citations 33 citations 2026-06-04T08:55:22.739355

Show evidence (2 references)

PMID:24815737 SUPPORT Human Clinical

"Clonally expanded CD19(+)CD27(+)CD20(-)CD38(hi) plasmablasts are a hallmark of active IgG4-RD."

Human B-cell repertoire data support plasmablast expansion as a central disease-activity feature in the canonical adaptive immune model.

PMID:28166682 SUPPORT Other

"CD4+ CTLs in affected tissues secrete pro-fibrotic cytokines including IL-1β, TGF-β1, and IFN-γ as well as cytolytic molecules such as perforin and granzymes A and B."

Review-level synthesis supports CD4+ cytotoxic T cells as the immune-cell arm most directly linked to fibrogenic mediator production.

Innate-First Bystander Activation Model

innate_first_bystander_model ALTERNATIVE

A competing or superimposed model in which innate immune activation in susceptible tissues precedes classical autoantigen-driven adaptive immunity, with plasmablast expansion and IgG4 class switching arising partly as downstream bystander responses.

Show evidence (1 reference)

PMID:31339007 PARTIAL Other

"TLR-7-expressing M2 macrophages may promote the activation of Th2 immune responses via IL-33 secretion in IgG4-RD."

Mixed human tissue, in vitro, and transgenic mouse evidence supports an innate TLR7/M2 macrophage axis as an alternative or upstream amplifier, but it does not replace the adaptive plasmablast/CTL model.

Discussions and Knowledge Gaps

What dominant autoantigen, antigen family, or antigen-presenting context initiates the coupled plasmablast and CD4-positive T-cell response in IgG4-RD?

KNOWLEDGE GAP OPEN gap_igg4rd_dominant_autoantigen_identity

Attached to

pathophysiology#Candidate Autoantigen Recognition and Antigen Presentation pathophysiology#IgG4-Positive Plasmablast Expansion pathophysiology#CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production

The entry now models candidate autoantigen recognition upstream of both plasmablast expansion and fibrogenic CD4+ CTLs, but published candidate autoantigens explain only subsets. Resolving whether a dominant antigen, a per-organ antigen set, or bystander innate activation initiates the response would determine how specific the causal DAG should be.

Proposed experiments

Paired BCR/TCR and autoantigen discovery across active IgG4-RD lesions

paired repertoire and antigen-discovery experiment

exp_igg4rd_paired_bcr_tcr_antigen_discovery

From paired blood and affected-organ biopsies, sequence plasmablast BCRs and expanded CD4+ CTL TCRs, express dominant antibodies and TCRs, and test candidate antigens by proteome arrays, immunoprecipitation-mass spectrometry, and antigen-presentation assays.

Model systems

Active human IgG4-RD blood and affected-organ biopsy pairs

Prospective patient samples spanning pancreatobiliary, salivary/lacrimal, renal, retroperitoneal, and vascular IgG4-RD manifestations.

OTHER

human NCBITaxon:9606

plasmablast CL:0000980 CD4-positive cytotoxic T lymphocyte CL:0000624

Readouts

Shared and organ-restricted antigen specificity

pathophysiology#Candidate Autoantigen Recognition and Antigen Presentation

Concordance between dominant plasmablast antibody specificity, expanded lesional TCR recognition, and organ expression of candidate antigens.

B cell receptor sequencing T cell receptor sequencing immunoprecipitation mass spectrometry

Direction: POSITIVE

Decision criterion

A dominant autoantigen model is supported if recurrent antigen specificities are shared across independent patients and mechanistically connect plasmablast BCRs to lesional CD4+ T-cell activation; a per-organ model is supported if specificity tracks organ tropism instead.

Would support

Show evidence (2 references)

PMID:31612628 SUPPORT Human Clinical

"While these findings suggest an underlying importance for B cell tolerance and the potential pathogenicity of autoantibodies in IgG4-RD, they also highlight the unmet need in identifying a dominant and specific antigen that may drive the pathogenesis of IgG4-RD."

The validation cohort explicitly frames dominant antigen identity as an unmet need despite several candidate autoantigens.

PMID:24815737 SUPPORT Human Clinical

"disease pathogenesis is linked to de novo recruitment of naive B cells into T cell-dependent responses by CD4(+) T cells, likely driving a self-reactive disease process."

The B-cell repertoire study motivates a specific antigen-discovery gap connecting plasmablasts to CD4+ T-cell-dependent responses.

Why do shared plasmablast, IgG4 class-switching, and CD4-positive cytotoxic-T-cell programs produce different organ manifestations such as pancreatitis, cholangitis, retroperitoneal fibrosis, kidney disease, and salivary/lacrimal gland enlargement?

KNOWLEDGE GAP OPEN gap_igg4rd_organ_tropism_and_fibroinflammation

Attached to

pathophysiology#Storiform Fibrosis pathophysiology#Organ-Specific Fibroinflammatory Injury

IgG4-RD has a conserved fibroinflammatory histology, but the current model cannot yet explain why particular organs are targeted in individual patients. Organ-restricted antigens, epithelial-barrier functions, chemokine niches, and local stromal repair programs remain plausible but incompletely connected mechanisms.

Proposed experiments

Multi-organ single-cell immune-stromal map of IgG4-RD lesions

multi-organ single-cell spatial profiling study

exp_igg4rd_multi_organ_single_cell_stromal_immune_map

Compare affected pancreas, bile duct, kidney, retroperitoneum, and salivary/lacrimal tissues using single-cell RNA sequencing, spatial transcriptomics, BCR/TCR sequencing, and autoantigen staining to separate shared fibroinflammatory circuitry from organ-specific injury programs.

Model systems

Human IgG4-RD affected-organ biopsy cohort

Cross-organ biopsy cohort with matched blood, histopathology, serum autoantibody, and treatment-response metadata.

OTHER

human NCBITaxon:9606

Readouts

Organ-specific antigen and stromal activation signatures

pathophysiology#Organ-Specific Fibroinflammatory Injury

Spatial colocalization of candidate autoantigens, plasmablasts/plasma cells, CD4+ CTLs, macrophages, fibroblasts, myofibroblasts, and extracellular matrix gene programs.

single-cell RNA sequencing spatial transcriptomics

Direction: POSITIVE

Decision criterion

Organ tropism is supported as antigen/barrier-driven if candidate autoantigen expression and barrier injury localize with immune clonotypes and stromal activation in the affected organ more strongly than in unaffected or disease-control tissue.

Would support

pathophysiology#Organ-Specific Fibroinflammatory Injury pathophysiology#Storiform Fibrosis

Show evidence (2 references)

PMID:38524667 PARTIAL In Vitro

"This makes it tempting to speculate that a decreased epithelial barrier function with attraction of immune cells and impaired bicarbonate secretion as a result of dysfunction of laminin 511 by autoantibody binding could potentially be a common systemic pathogenic mechanism in a subset of..."

Cholangitis data support a plausible epithelial-barrier mechanism, while the authors frame it as subset-level and still partly speculative.

PMID:34718050 PARTIAL In Vitro

"Binding of patient-derived annexin A11 autoantibodies inhibits annexin A11 function, possibly contributing to bile duct damage by weakening the biliary bicarbonate umbrella in patients with IRC."

Annexin A11 evidence supplies an organ-specific bile-duct injury model but does not explain non-biliary organ tropism.

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Pathophysiology

Candidate Autoantigen Recognition and Antigen Presentation

IgG4-RD shows autoreactive B-lineage responses, but a universal initiating autoantigen has not been identified. Candidate antigens such as galectin-3, PHB1, annexin A11, and laminin 511-E8 define subsets and provide mechanistic leads for how B cells or plasmablasts could present antigen to CD4-positive T-cell axes.

Plasmablast-Autoantigen Fibrosis Driver Model

B cell CL:0000236

Antigen processing and presentation GO:0019882 B cell activation GO:0042113

Downstream

Tfh-Mediated IgG4 Class Switching and Plasma Cell Differentiation Antigen-experienced B cells are inferred to recruit T-cell help that promotes plasmablast differentiation and IgG4 class switching.

CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production Antigen-presenting B-lineage cells may sustain CD4+ cytotoxic T-cell expansion, but the dominant self-antigens and tissue-specific intermediates remain unresolved.

Show evidence (2 references)

PMID:24815737 SUPPORT Human Clinical

"Cloning and expression of immunoglobulin heavy and light chain genes from expanded plasmablasts at the peak of disease reveals that disease-associated IgG4 antibodies are self-reactive."

Plasmablast-derived antibody cloning supports autoreactivity in the active disease B-lineage response.

PMID:31612628 PARTIAL Human Clinical

"Of these 86 patients, 32 (37%) had IgG4 antibodies to ≥1 of the 4 autoantigens and 12 (14%) showed reactivity with ≥2 of the tested antigens."

Candidate autoantigens are documented, but the study also shows that none is a universal IgG4-RD antigen.

Tfh-Mediated IgG4 Class Switching and Plasma Cell Differentiation

Follicular helper T cells provide B-cell help in germinal centers, promoting plasmablast differentiation and IgG4 class switching that contributes to the IgG4-positive plasma-cell-rich tissue infiltrate.

Plasmablast-Autoantigen Fibrosis Driver Model

T follicular helper cell CL:0002038 B cell CL:0000236

Isotype switching GO:0045190 Plasma cell differentiation GO:0002317

Downstream

IgG4-Positive Plasmablast Expansion Tfh-driven B-cell help promotes plasmablast differentiation and IgG4 class switching in the canonical adaptive immune model.

Show evidence (2 references)

DOI:10.3389/fimmu.2024.1413860 SUPPORT Other

"T cell immunity plays a crucial role in the pathogenesis of IgG4-RD, and follicular helper T cells (Tfh) are particularly important in germinal center (GC) formation, plasmablast differentiation, and IgG4 class-switching."

This review supports a distinct Tfh-mediated B-cell help node upstream of IgG4-positive plasma-cell accumulation.

PMID:29253269 SUPPORT Human Clinical

"The association found between Tfh cells and plasmablasts, linked with biological plausibility, suggests that Tfh cells contribute to the pathogenesis of IgG4-RD."

Human immunophenotyping supports the modeled Tfh-plasmablast axis upstream of IgG4 class switching and plasmablast expansion.

IgG4-Positive Plasmablast Expansion

Circulating plasmablasts, many of which are IgG4-positive and clonally expanded, are elevated in active disease and fall with B-cell depletion. They are modeled separately from mature tissue plasma cells because they report disease activity, relapse biology, and CD19-targeted therapeutic vulnerability.

Plasmablast-Autoantigen Fibrosis Driver Model

Plasmablast CL:0000980

B cell activation GO:0042113 Isotype switching GO:0045190

Downstream

IgG4-Positive Plasma Cell Infiltration Expanded IgG4-positive plasmablasts feed the antibody-secreting plasma-cell compartment that accumulates in affected tissues.

CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production Activated B cells and plasmablasts may collaborate with CD4+ CTLs, plausibly through antigen presentation, but the antigenic and tissue-specific intermediates remain unresolved.

Show evidence (2 references)

PMID:24817416 SUPPORT Human Clinical

"Circulating plasmablasts are elevated in active IgG4-RD, even in patients with normal serum IgG4 concentrations."

Human flow-cytometry data support plasmablast expansion as a distinct active-disease B-lineage node.

PMID:24815737 SUPPORT Human Clinical

"These expanded plasmablasts are oligoclonal and exhibit extensive somatic hypermutation, and their numbers decrease after rituximab-mediated B-cell depletion therapy; this loss correlates with disease remission."

Repertoire sequencing and treatment-response data support a clonally expanded, disease-linked plasmablast compartment.

IgG4-Positive Plasma Cell Infiltration

Abundant IgG4-bearing plasma cells infiltrate affected tissues, though the pathogenic role of IgG4 antibodies themselves remains debated.

Plasma cell CL:0000786

Immune response GO:0006955 Inflammatory response GO:0006954

Show evidence (2 references)

PMID:25988916 SUPPORT Human Clinical

"IgG4-related disease (IgG4-RD) has emerged over the last decade as a unique immune-mediated condition that links multiple fibro-inflammatory disorders previously regarded as separate entities"

Establishes IgG4-RD as a unified immune-mediated fibroinflammatory condition.

PMID:25988916 SUPPORT Human Clinical

"The gold-standard for the diagnosis of IgG4-RD, regardless of the organ(s) involved, is the identification of typical histopathology features (e.g., lymphoplasmacytic infiltrate, storiform fibrosis, obliterative phlebitis) in the context of a significant IgG4+ plasma cell infiltrate"

Confirms lymphoplasmacytic infiltrate with IgG4+ plasma cells as the histopathological hallmark.

CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production

Clonally expanded CD4-positive cytotoxic T lymphocytes infiltrate IgG4-RD lesions and produce inflammatory and profibrotic mediators, including IL-1beta, TGF-beta1, and IFN-gamma in salivary and lacrimal gland disease.

Plasmablast-Autoantigen Fibrosis Driver Model

CD4-positive cytotoxic T lymphocyte CL:0000624

Cytokine production GO:0001816 Inflammatory response GO:0006954

Downstream

Storiform Fibrosis Profibrotic cytokine-secreting CD4+ CTLs provide an immune-cell mechanism for chronic inflammation and fibrosis.

Show evidence (3 references)

PMID:26971690 SUPPORT Human Clinical

"IgG4-RD is prominently linked to clonally expanded IL-1β- and TGF-β1-secreting CD4(+) CTLs in both peripheral blood and inflammatory tissue lesions."

Human cohort data support clonally expanded IL-1beta- and TGF-beta1-secreting CD4+ CTLs as a distinct pathogenic effector node.

PMID:27358392 SUPPORT Human Clinical

"A large fraction of CD4+GZMA+ CTLs in SMGs from patients with IgG4-DS secreted IFN-γ."

This salivary-gland IgG4-RD study supports IFN-gamma secretion by lesional CD4+ cytotoxic T cells.

PMID:32485263 SUPPORT Human Clinical

"CD4+CTLs and CD8+CTLs may induce apoptotic cell death in tissues of patients with IgG4-RD with preferential targeting of nonendothelial, nonimmune cells of mesenchymal origin."

Human blood and tissue analyses link cytotoxic T-cell effector programs to mesenchymal-cell injury, a plausible bridge to fibrotic repair.

Storiform Fibrosis

A characteristic cartwheel or whorled pattern of fibrosis is a histopathological hallmark. Activated fibroblasts and myofibroblasts are driven by profibrotic cytokines from CD4+ CTLs, leading to progressive tissue remodeling and organ dysfunction.

Plasmablast-Autoantigen Fibrosis Driver Model

Fibroblast CL:0000057 Myofibroblast CL:0000186

TGF-beta Receptor Signaling GO:0007179 ↑ INCREASED ECM Organization GO:0030198 ↑ INCREASED Collagen fibril organization GO:0030199 ↑ INCREASED

Downstream

Organ-Specific Fibroinflammatory Injury Persistent fibroblast and myofibroblast activation remodels affected organ tissue, with the clinical pattern shaped by organ-specific antigen, barrier, and injury contexts.

Show evidence (1 reference)

PMID:25988916 SUPPORT Human Clinical

"The major histopathologic features include a dense lymphoplasmacytic infiltrate, fibrosis that has a storiform pattern in focal (or diffuse) areas, and obliterative phlebitis."

Storiform fibrosis identified as one of the three major histopathological features of IgG4-RD.

Organ-Specific Fibroinflammatory Injury

The same fibroinflammatory framework produces organ-specific syndromes such as autoimmune pancreatitis and IgG4-related cholangitis. Current evidence supports per-organ antigen and epithelial-barrier mechanisms in subsets, rather than a single universal tissue-tropism mechanism.

Show evidence (3 references)

PMID:30089633 SUPPORT Other

"Autoimmune pancreatitis (AIP), a major manifestation of immunoglobulin G4-related disease (IgG4-RD), is an immune-mediated disorder, but the target autoantigens are still unknown."

Pancreatic disease illustrates organ-specific autoimmune injury while retaining uncertainty about the full target-antigen set.

PMID:38524667 SUPPORT In Vitro

"Laminin 511-E8 is an autoantigen in subsets of individuals with IRC."

Human serum and cholangiocyte experiments support a bile-duct-specific autoantigen/barrier-injury mechanism in a subset of IgG4-related cholangitis.

PMID:34718050 SUPPORT In Vitro

"Anti-annexin A11 autoantibodies may contribute to the pathogenesis of IRC by weakening the 'biliary bicarbonate umbrella'."

This supports an organ-specific cholangiocyte-protection mechanism for bile-duct injury in IgG4-related cholangitis.

✶

Histopathology

Dense Lymphoplasmacytic Infiltrate with IgG4-Positive Plasma Cells VERY_FREQUENT

Tissue biopsy shows a dense lymphoplasmacytic infiltrate with increased IgG4-positive plasma cells or an increased IgG4+/IgG+ plasma-cell ratio.

Show evidence (1 reference)

PMID:25988916 SUPPORT Human Clinical

"The pathology diagnosis of IgG4-RD is predicated upon the presence of both specific histopathologic features and an increased number of IgG4+ plasma cells (or IgG4+/IgG+ ratio) in affected tissue"

This cohort-based pathology description supports IgG4-positive lymphoplasmacytic infiltration as a defining tissue finding.

Storiform Fibrosis FREQUENT

Fibrosis in a storiform, whorled, or cartwheel pattern is one of the characteristic microscopic features of IgG4-RD.

Show evidence (1 reference)

PMID:25988916 SUPPORT Human Clinical

"The major histopathologic features include a dense lymphoplasmacytic infiltrate, fibrosis that has a storiform pattern in focal (or diffuse) areas, and obliterative phlebitis."

The quoted pathology summary names storiform fibrosis as a major IgG4-RD histopathologic feature.

Obliterative Phlebitis FREQUENT

Obliterative phlebitis, venous inflammation with luminal obliteration, is part of the classic IgG4-RD histopathology triad.

Show evidence (1 reference)

PMID:25988916 SUPPORT Human Clinical

"The major histopathologic features include a dense lymphoplasmacytic infiltrate, fibrosis that has a storiform pattern in focal (or diffuse) areas, and obliterative phlebitis."

The quoted pathology summary names obliterative phlebitis as a major IgG4-RD histopathologic feature.

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Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Digestive 4

Autoimmune Pancreatitis VERY_FREQUENT Pancreatitis HP:0001733

Type 1 autoimmune pancreatitis is the most common manifestation. Presents with painless jaundice, diffuse pancreatic enlargement, and elevated serum IgG4.

Sclerosing Cholangitis FREQUENT Sclerosing cholangitis HP:0030991

IgG4-related sclerosing cholangitis can mimic primary sclerosing cholangitis or cholangiocarcinoma but responds to corticosteroids.

Jaundice FREQUENT Jaundice HP:0000952

Retroperitoneal Fibrosis FREQUENT Retroperitoneal fibrosis HP:0005200

Genitourinary 1

Renal Insufficiency OCCASIONAL Renal insufficiency HP:0000083

IgG4-related tubulointerstitial nephritis or membranous nephropathy can lead to progressive renal dysfunction.

Head and Neck 1

Enlarged Lacrimal Glands FREQUENT Enlarged lacrimal glands HP:0007734

Growth 1

Weight Loss FREQUENT Weight loss HP:0001824

💊

Medical Actions

Glucocorticoids

Action: glucocorticoid therapy Ontology label: Systemic Corticosteroid Therapy NCIT:C122080

First-line therapy with excellent initial response rates. However, sustained remission is achieved in only about 23% of patients, with most relapsing upon steroid discontinuation.

Show evidence (2 references)

PMID:25988916 SUPPORT Human Clinical

"Treatment with glucocorticoids failed to produce sustained remission in 77% of patients."

While glucocorticoids are first-line, they fail to produce sustained remission in the majority of patients.

PMID:25809420 SUPPORT Human Clinical

"International Consensus Guidance Statement on the Management and Treatment of IgG4-Related Disease."

International consensus guidelines established for IgG4-RD management.

Rituximab

Action: rituximab therapy Ontology label: Pharmacotherapy NCIT:C15986

Agent: rituximab NCIT:C1702

Anti-CD20 monoclonal antibody used for relapsing or refractory disease. Effective in inducing remission and reducing serum IgG4 levels by depleting B cell precursors of IgG4-producing plasma cells.

Inebilizumab

Action: Pharmacotherapy NCIT:C15986

Agent: inebilizumab NCIT:C88283

Anti-CD19 monoclonal antibody evaluated in the Phase 3 MITIGATE trial (NCT04540497). CD19 targeting reaches a broader B-lineage window than anti-CD20 therapy, including plasmablast-biased disease biology.

Mechanism Target:

INHIBITS IgG4-Positive Plasmablast Expansion — Inebilizumab depletes CD19-positive B-lineage cells, linking clinical benefit to suppression of the plasmablast/B-cell axis modeled upstream of tissue plasma-cell infiltration and fibrosis.

Show evidence (1 reference)

PMID:39541094 SUPPORT Human Clinical

"Inebilizumab targets and depletes CD19+ B cells and may be effective for treating patients with IgG4-related disease."

The Phase 3 trial describes CD19-positive B-cell depletion as the mechanism motivating inebilizumab in IgG4-RD.

Show evidence (1 reference)

PMID:39541094 SUPPORT Human Clinical

"Inebilizumab reduced the risk of flares of IgG4-related disease and increased the likelihood of flare-free complete remission at 1 year, confirming the role of CD19-targeted B-cell depletion as a potential treatment for IgG4-related disease."

MITIGATE provides randomized Phase 3 evidence that CD19-targeted B-cell depletion reduces IgG4-RD flares.

🔬

Biochemical Markers

Serum IgG4 (Elevated)

Context: Elevated serum IgG4 (>135 mg/dL) is found in 51-70% of patients with active disease, but is neither sensitive nor specific.

Show evidence (2 references)

PMID:25988916 SUPPORT Human Clinical

"Only 51% of the patients with active disease had elevated serum IgG4 concentrations."

Large cohort study showing that nearly half of active IgG4-RD patients have normal serum IgG4, demonstrating imperfect sensitivity.

PMID:25988916 SUPPORT Human Clinical

"patients with active disease and elevated serum IgG4 concentrations were older, had a higher IgG4-RD RI score, a greater number of organs involved, lower complement levels, higher absolute eosinophil counts, and higher IgE levels"

Elevated serum IgG4 identifies a subset with more severe disease.

Total IgG (Elevated)

Context: Polyclonal hypergammaglobulinemia is common.

Complement C3 and C4 (Decreased)

Context: Hypocomplementemia may occur, particularly in patients with renal involvement, suggesting immune complex-mediated damage.

Show evidence (1 reference)

PMID:25988916 SUPPORT Human Clinical

"patients with active disease and elevated serum IgG4 concentrations were older, had a higher IgG4-RD RI score, a greater number of organs involved, lower complement levels"

Lower complement levels associated with more severe IgG4-RD phenotype.

{ }

Source YAML

click to show

name: IgG4-Related Disease
creation_date: "2026-03-06T00:00:00Z"
updated_date: "2026-05-09T20:30:53Z"
category: Autoimmune
disease_term:
  preferred_term: IgG4-related disease
  term:
    id: MONDO:0017287
    label: immunoglobulin G4-related sclerosing disease
parents:
- Autoimmune Disease
- Fibroinflammatory Disease
description: >-
  A rare immune-mediated fibroinflammatory condition characterized by
  tumefactive lesions, a dense lymphoplasmacytic infiltrate rich in
  IgG4-positive plasma cells, storiform fibrosis, and often elevated serum
  IgG4 concentrations. The disease can affect virtually any organ but most
  commonly involves the pancreas (autoimmune pancreatitis), salivary and
  lacrimal glands, bile ducts, kidneys, retroperitoneum, and aorta. Left
  untreated, it leads to progressive fibrosis and organ damage.
has_subtypes:
- name: IgG4-Related Autoimmune Pancreatitis (Type 1 AIP)
  description: >-
    The most common organ manifestation, presenting as diffuse or focal
    pancreatic enlargement with characteristic periductal lymphoplasmacytic
    infiltrate. Often presents with obstructive jaundice.
- name: IgG4-Related Dacryoadenitis and Sialadenitis
  description: >-
    Bilateral enlargement of lacrimal and/or salivary glands (historically
    called Mikulicz disease). Presents with painless symmetrical gland
    swelling.
mechanistic_hypotheses:
- hypothesis_group_id: plasmablast_autoantigen_fibrosis_driver_model
  hypothesis_label: Plasmablast-Autoantigen Fibrosis Driver Model
  status: CANONICAL
  description: >-
    A still-incomplete adaptive immune model in which unresolved autoantigen or
    innate triggers expand B-cell/plasmablast and T-cell axes; Tfh cells promote
    IgG4 class switching, plasmablasts mark and sustain the B-lineage response,
    and CD4-positive cytotoxic T cells provide fibrogenic cytokines that drive
    storiform fibrosis and organ injury.
  evidence:
  - reference: PMID:24815737
    reference_title: De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Clonally expanded CD19(+)CD27(+)CD20(-)CD38(hi) plasmablasts are a
      hallmark of active IgG4-RD.
    explanation: >-
      Human B-cell repertoire data support plasmablast expansion as a central
      disease-activity feature in the canonical adaptive immune model.
  - reference: PMID:28166682
    reference_title: Clonally expanded cytotoxic CD4(+) T cells and the pathogenesis of IgG4-related disease.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      CD4+ CTLs in affected tissues secrete pro-fibrotic cytokines including
      IL-1β, TGF-β1, and IFN-γ as well as cytolytic molecules such as perforin
      and granzymes A and B.
    explanation: >-
      Review-level synthesis supports CD4+ cytotoxic T cells as the immune-cell
      arm most directly linked to fibrogenic mediator production.
- hypothesis_group_id: innate_first_bystander_model
  hypothesis_label: Innate-First Bystander Activation Model
  status: ALTERNATIVE
  description: >-
    A competing or superimposed model in which innate immune activation in
    susceptible tissues precedes classical autoantigen-driven adaptive immunity,
    with plasmablast expansion and IgG4 class switching arising partly as
    downstream bystander responses.
  evidence:
  - reference: PMID:31339007
    reference_title: Activated M2 Macrophages Contribute to the Pathogenesis of IgG4-Related Disease via Toll-like Receptor 7/Interleukin-33 Signaling.
    supports: PARTIAL
    evidence_source: OTHER
    snippet: >-
      TLR-7-expressing M2 macrophages may promote the activation of Th2 immune
      responses via IL-33 secretion in IgG4-RD.
    explanation: >-
      Mixed human tissue, in vitro, and transgenic mouse evidence supports an
      innate TLR7/M2 macrophage axis as an alternative or upstream amplifier,
      but it does not replace the adaptive plasmablast/CTL model.
pathophysiology:
- name: Candidate Autoantigen Recognition and Antigen Presentation
  description: >-
    IgG4-RD shows autoreactive B-lineage responses, but a universal initiating
    autoantigen has not been identified. Candidate antigens such as galectin-3,
    PHB1, annexin A11, and laminin 511-E8 define subsets and provide
    mechanistic leads for how B cells or plasmablasts could present antigen to
    CD4-positive T-cell axes.
  role: trigger
  cell_types:
  - preferred_term: B cell
    term:
      id: CL:0000236
      label: B cell
  biological_processes:
  - preferred_term: Antigen processing and presentation
    term:
      id: GO:0019882
      label: antigen processing and presentation
  - preferred_term: B cell activation
    term:
      id: GO:0042113
      label: B cell activation
  downstream:
  - target: Tfh-Mediated IgG4 Class Switching and Plasma Cell Differentiation
    description: Antigen-experienced B cells are inferred to recruit T-cell help that promotes plasmablast differentiation and IgG4 class switching.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  - target: CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production
    description: Antigen-presenting B-lineage cells may sustain CD4+ cytotoxic T-cell expansion, but the dominant self-antigens and tissue-specific intermediates remain unresolved.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:24815737
    reference_title: De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cloning and expression of immunoglobulin heavy and light chain genes from
      expanded plasmablasts at the peak of disease reveals that
      disease-associated IgG4 antibodies are self-reactive.
    explanation: >-
      Plasmablast-derived antibody cloning supports autoreactivity in the
      active disease B-lineage response.
  - reference: PMID:31612628
    reference_title: Disease Severity Linked to Increase in Autoantibody Diversity in IgG4-Related Disease.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Of these 86 patients, 32 (37%) had IgG4 antibodies to ≥1 of the 4
      autoantigens and 12 (14%) showed reactivity with ≥2 of the tested
      antigens.
    explanation: >-
      Candidate autoantigens are documented, but the study also shows that none
      is a universal IgG4-RD antigen.
- name: Tfh-Mediated IgG4 Class Switching and Plasma Cell Differentiation
  description: >-
    Follicular helper T cells provide B-cell help in germinal centers,
    promoting plasmablast differentiation and IgG4 class switching that
    contributes to the IgG4-positive plasma-cell-rich tissue infiltrate.
  cell_types:
  - preferred_term: T follicular helper cell
    term:
      id: CL:0002038
      label: T follicular helper cell
  - preferred_term: B cell
    term:
      id: CL:0000236
      label: B cell
  biological_processes:
  - preferred_term: Isotype switching
    term:
      id: GO:0045190
      label: isotype switching
  - preferred_term: Plasma cell differentiation
    term:
      id: GO:0002317
      label: plasma cell differentiation
  downstream:
  - target: IgG4-Positive Plasmablast Expansion
    description: Tfh-driven B-cell help promotes plasmablast differentiation and IgG4 class switching in the canonical adaptive immune model.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  evidence:
  - reference: DOI:10.3389/fimmu.2024.1413860
    reference_title: Pathogenic roles of follicular helper T cells in IgG4-related disease and implications for potential therapy
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      T cell immunity plays a crucial role in the pathogenesis of IgG4-RD,
      and follicular helper T cells (Tfh) are particularly important in
      germinal center (GC) formation, plasmablast differentiation, and IgG4
      class-switching.
    explanation: >-
      This review supports a distinct Tfh-mediated B-cell help node upstream
      of IgG4-positive plasma-cell accumulation.
  - reference: PMID:29253269
    reference_title: Correlation of T follicular helper cells and plasmablasts with the development of organ involvement in patients with IgG4-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The association found between Tfh cells and plasmablasts, linked with
      biological plausibility, suggests that Tfh cells contribute to the
      pathogenesis of IgG4-RD.
    explanation: >-
      Human immunophenotyping supports the modeled Tfh-plasmablast axis
      upstream of IgG4 class switching and plasmablast expansion.
- name: IgG4-Positive Plasmablast Expansion
  description: >-
    Circulating plasmablasts, many of which are IgG4-positive and clonally
    expanded, are elevated in active disease and fall with B-cell depletion.
    They are modeled separately from mature tissue plasma cells because they
    report disease activity, relapse biology, and CD19-targeted therapeutic
    vulnerability.
  cell_types:
  - preferred_term: Plasmablast
    term:
      id: CL:0000980
      label: plasmablast
  biological_processes:
  - preferred_term: B cell activation
    term:
      id: GO:0042113
      label: B cell activation
  - preferred_term: Isotype switching
    term:
      id: GO:0045190
      label: isotype switching
  downstream:
  - target: IgG4-Positive Plasma Cell Infiltration
    description: Expanded IgG4-positive plasmablasts feed the antibody-secreting plasma-cell compartment that accumulates in affected tissues.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  - target: CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production
    description: Activated B cells and plasmablasts may collaborate with CD4+ CTLs, plausibly through antigen presentation, but the antigenic and tissue-specific intermediates remain unresolved.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:24817416
    reference_title: Plasmablasts as a biomarker for IgG4-related disease, independent of serum IgG4 concentrations.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Circulating plasmablasts are elevated in active IgG4-RD, even in patients
      with normal serum IgG4 concentrations.
    explanation: >-
      Human flow-cytometry data support plasmablast expansion as a distinct
      active-disease B-lineage node.
  - reference: PMID:24815737
    reference_title: De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      These expanded plasmablasts are oligoclonal and exhibit extensive somatic
      hypermutation, and their numbers decrease after rituximab-mediated B-cell
      depletion therapy; this loss correlates with disease remission.
    explanation: >-
      Repertoire sequencing and treatment-response data support a clonally
      expanded, disease-linked plasmablast compartment.
- name: IgG4-Positive Plasma Cell Infiltration
  description: >-
    Abundant IgG4-bearing plasma cells infiltrate affected tissues, though
    the pathogenic role of IgG4 antibodies themselves remains debated.
  cell_types:
  - preferred_term: Plasma cell
    term:
      id: CL:0000786
      label: plasma cell
  biological_processes:
  - preferred_term: Immune response
    term:
      id: GO:0006955
      label: immune response
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      IgG4-related disease (IgG4-RD) has emerged over the last decade as a
      unique immune-mediated condition that links multiple fibro-inflammatory
      disorders previously regarded as separate entities
    explanation: >-
      Establishes IgG4-RD as a unified immune-mediated fibroinflammatory
      condition.
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The gold-standard for the diagnosis of IgG4-RD, regardless of the
      organ(s) involved, is the identification of typical histopathology
      features (e.g., lymphoplasmacytic infiltrate, storiform fibrosis,
      obliterative phlebitis) in the context of a significant IgG4+ plasma
      cell infiltrate
    explanation: >-
      Confirms lymphoplasmacytic infiltrate with IgG4+ plasma cells as the
      histopathological hallmark.
- name: CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production
  description: >-
    Clonally expanded CD4-positive cytotoxic T lymphocytes infiltrate IgG4-RD
    lesions and produce inflammatory and profibrotic mediators, including
    IL-1beta, TGF-beta1, and IFN-gamma in salivary and lacrimal gland disease.
  cell_types:
  - preferred_term: CD4-positive cytotoxic T lymphocyte
    term:
      id: CL:0000624
      label: CD4-positive, alpha-beta T cell
  biological_processes:
  - preferred_term: Cytokine production
    term:
      id: GO:0001816
      label: cytokine production
  - preferred_term: Inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
  downstream:
  - target: Storiform Fibrosis
    description: Profibrotic cytokine-secreting CD4+ CTLs provide an immune-cell mechanism for chronic inflammation and fibrosis.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:26971690
    reference_title: Clonal expansion of CD4(+) cytotoxic T lymphocytes in patients with IgG4-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      IgG4-RD is prominently linked to clonally expanded IL-1β- and
      TGF-β1-secreting CD4(+) CTLs in both peripheral blood and inflammatory
      tissue lesions.
    explanation: >-
      Human cohort data support clonally expanded IL-1beta- and
      TGF-beta1-secreting CD4+ CTLs as a distinct pathogenic effector node.
  - reference: PMID:27358392
    reference_title: Lesional CD4+ IFN-γ+ cytotoxic T lymphocytes in IgG4-related dacryoadenitis and sialoadenitis.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      A large fraction of CD4+GZMA+ CTLs in SMGs from patients with IgG4-DS
      secreted IFN-γ.
    explanation: >-
      This salivary-gland IgG4-RD study supports IFN-gamma secretion by
      lesional CD4+ cytotoxic T cells.
  - reference: PMID:32485263
    reference_title: CD4(+) and CD8(+) cytotoxic T lymphocytes may induce mesenchymal cell apoptosis in IgG(4)-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      CD4+CTLs and CD8+CTLs may induce apoptotic cell death in tissues of
      patients with IgG4-RD with preferential targeting of nonendothelial,
      nonimmune cells of mesenchymal origin.
    explanation: >-
      Human blood and tissue analyses link cytotoxic T-cell effector programs
      to mesenchymal-cell injury, a plausible bridge to fibrotic repair.
- name: Storiform Fibrosis
  conforms_to: "fibrotic_response#Mesenchymal Cell Activation"
  description: >-
    A characteristic cartwheel or whorled pattern of fibrosis is a
    histopathological hallmark. Activated fibroblasts and myofibroblasts
    are driven by profibrotic cytokines from CD4+ CTLs, leading to
    progressive tissue remodeling and organ dysfunction.
  cell_types:
  - preferred_term: Fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  - preferred_term: Myofibroblast
    term:
      id: CL:0000186
      label: myofibroblast cell
  biological_processes:
  - preferred_term: TGF-beta Receptor Signaling
    term:
      id: GO:0007179
      label: transforming growth factor beta receptor signaling pathway
    modifier: INCREASED
  - preferred_term: ECM Organization
    term:
      id: GO:0030198
      label: extracellular matrix organization
    modifier: INCREASED
  - preferred_term: Collagen fibril organization
    term:
      id: GO:0030199
      label: collagen fibril organization
    modifier: INCREASED
  downstream:
  - target: Organ-Specific Fibroinflammatory Injury
    description: Persistent fibroblast and myofibroblast activation remodels affected organ tissue, with the clinical pattern shaped by organ-specific antigen, barrier, and injury contexts.
    hypothesis_groups:
    - plasmablast_autoantigen_fibrosis_driver_model
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The major histopathologic features include a dense lymphoplasmacytic
      infiltrate, fibrosis that has a storiform pattern in focal (or diffuse)
      areas, and obliterative phlebitis.
    explanation: >-
      Storiform fibrosis identified as one of the three major
      histopathological features of IgG4-RD.
- name: Organ-Specific Fibroinflammatory Injury
  description: >-
    The same fibroinflammatory framework produces organ-specific syndromes such
    as autoimmune pancreatitis and IgG4-related cholangitis. Current evidence
    supports per-organ antigen and epithelial-barrier mechanisms in subsets,
    rather than a single universal tissue-tropism mechanism.
  role: consequence
  evidence:
  - reference: PMID:30089633
    reference_title: Laminin 511 is a target antigen in autoimmune pancreatitis.
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Autoimmune pancreatitis (AIP), a major manifestation of immunoglobulin
      G4-related disease (IgG4-RD), is an immune-mediated disorder, but the
      target autoantigens are still unknown.
    explanation: >-
      Pancreatic disease illustrates organ-specific autoimmune injury while
      retaining uncertainty about the full target-antigen set.
  - reference: PMID:38524667
    reference_title: Laminin 511-E8, an autoantigen in IgG4-related cholangitis, contributes to cholangiocyte protection.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Laminin 511-E8 is an autoantigen in subsets of individuals with IRC.
    explanation: >-
      Human serum and cholangiocyte experiments support a bile-duct-specific
      autoantigen/barrier-injury mechanism in a subset of IgG4-related
      cholangitis.
  - reference: PMID:34718050
    reference_title: Role of the IgG4-related cholangitis autoantigen annexin A11 in cholangiocyte protection.
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      Anti-annexin A11 autoantibodies may contribute to the pathogenesis of IRC
      by weakening the 'biliary bicarbonate umbrella'.
    explanation: >-
      This supports an organ-specific cholangiocyte-protection mechanism for
      bile-duct injury in IgG4-related cholangitis.
histopathology:
- name: Dense Lymphoplasmacytic Infiltrate with IgG4-Positive Plasma Cells
  finding_term:
    preferred_term: Dense IgG4-positive lymphoplasmacytic infiltrate
    term:
      id: NCIT:C35984
      label: Lymphoplasmacytic Infiltrate
  diagnostic: true
  frequency: VERY_FREQUENT
  description: >-
    Tissue biopsy shows a dense lymphoplasmacytic infiltrate with increased
    IgG4-positive plasma cells or an increased IgG4+/IgG+ plasma-cell ratio.
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The pathology diagnosis of IgG4-RD is predicated upon the presence of
      both specific histopathologic features and an increased number of IgG4+
      plasma cells (or IgG4+/IgG+ ratio) in affected tissue
    explanation: >-
      This cohort-based pathology description supports IgG4-positive
      lymphoplasmacytic infiltration as a defining tissue finding.
- name: Storiform Fibrosis
  finding_term:
    preferred_term: Storiform fibrosis
    term:
      id: NCIT:C3044
      label: Fibrosis
  diagnostic: true
  frequency: FREQUENT
  description: >-
    Fibrosis in a storiform, whorled, or cartwheel pattern is one of the
    characteristic microscopic features of IgG4-RD.
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The major histopathologic features include a dense lymphoplasmacytic
      infiltrate, fibrosis that has a storiform pattern in focal (or diffuse)
      areas, and obliterative phlebitis.
    explanation: >-
      The quoted pathology summary names storiform fibrosis as a major
      IgG4-RD histopathologic feature.
- name: Obliterative Phlebitis
  diagnostic: true
  frequency: FREQUENT
  description: >-
    Obliterative phlebitis, venous inflammation with luminal obliteration, is
    part of the classic IgG4-RD histopathology triad.
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The major histopathologic features include a dense lymphoplasmacytic
      infiltrate, fibrosis that has a storiform pattern in focal (or diffuse)
      areas, and obliterative phlebitis.
    explanation: >-
      The quoted pathology summary names obliterative phlebitis as a major
      IgG4-RD histopathologic feature.
phenotypes:
- category: Gastrointestinal
  name: Autoimmune Pancreatitis
  frequency: VERY_FREQUENT
  diagnostic: true
  notes: >-
    Type 1 autoimmune pancreatitis is the most common manifestation. Presents
    with painless jaundice, diffuse pancreatic enlargement, and elevated
    serum IgG4.
  phenotype_term:
    preferred_term: Pancreatitis
    term:
      id: HP:0001733
      label: Pancreatitis
- category: Ophthalmologic
  name: Enlarged Lacrimal Glands
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Enlarged lacrimal glands
    term:
      id: HP:0007734
      label: Enlarged lacrimal glands
- category: Hepatobiliary
  name: Sclerosing Cholangitis
  frequency: FREQUENT
  notes: >-
    IgG4-related sclerosing cholangitis can mimic primary sclerosing
    cholangitis or cholangiocarcinoma but responds to corticosteroids.
  phenotype_term:
    preferred_term: Sclerosing cholangitis
    term:
      id: HP:0030991
      label: Sclerosing cholangitis
- category: Hepatobiliary
  name: Jaundice
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Jaundice
    term:
      id: HP:0000952
      label: Jaundice
- category: Abdominal
  name: Retroperitoneal Fibrosis
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Retroperitoneal fibrosis
    term:
      id: HP:0005200
      label: Retroperitoneal fibrosis
- category: Renal
  name: Renal Insufficiency
  frequency: OCCASIONAL
  notes: >-
    IgG4-related tubulointerstitial nephritis or membranous nephropathy
    can lead to progressive renal dysfunction.
  phenotype_term:
    preferred_term: Renal insufficiency
    term:
      id: HP:0000083
      label: Renal insufficiency
- category: Constitutional
  name: Weight Loss
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Weight loss
    term:
      id: HP:0001824
      label: Weight loss
biochemical:
- name: Serum IgG4
  presence: Elevated
  context: >-
    Elevated serum IgG4 (>135 mg/dL) is found in 51-70% of patients with
    active disease, but is neither sensitive nor specific.
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Only 51% of the patients with active disease had elevated serum IgG4
      concentrations.
    explanation: >-
      Large cohort study showing that nearly half of active IgG4-RD patients
      have normal serum IgG4, demonstrating imperfect sensitivity.
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      patients with active disease and elevated serum IgG4 concentrations
      were older, had a higher IgG4-RD RI score, a greater number of organs
      involved, lower complement levels, higher absolute eosinophil counts,
      and higher IgE levels
    explanation: >-
      Elevated serum IgG4 identifies a subset with more severe disease.
- name: Total IgG
  presence: Elevated
  context: >-
    Polyclonal hypergammaglobulinemia is common.
- name: Complement C3 and C4
  presence: Decreased
  context: >-
    Hypocomplementemia may occur, particularly in patients with renal
    involvement, suggesting immune complex-mediated damage.
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      patients with active disease and elevated serum IgG4 concentrations
      were older, had a higher IgG4-RD RI score, a greater number of organs
      involved, lower complement levels
    explanation: >-
      Lower complement levels associated with more severe IgG4-RD phenotype.
treatments:
- name: Glucocorticoids
  description: >-
    First-line therapy with excellent initial response rates. However,
    sustained remission is achieved in only about 23% of patients, with
    most relapsing upon steroid discontinuation.
  evidence:
  - reference: PMID:25988916
    reference_title: "IgG4-Related Disease: Clinical and Laboratory Features in One Hundred Twenty-Five Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Treatment with glucocorticoids failed to produce sustained remission
      in 77% of patients.
    explanation: >-
      While glucocorticoids are first-line, they fail to produce sustained
      remission in the majority of patients.
  - reference: PMID:25809420
    reference_title: "International Consensus Guidance Statement on the Management and Treatment of IgG4-Related Disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      International Consensus Guidance Statement on the Management and
      Treatment of IgG4-Related Disease.
    explanation: >-
      International consensus guidelines established for IgG4-RD management.
  treatment_term:
    preferred_term: glucocorticoid therapy
    term:
      id: NCIT:C122080
      label: Systemic Corticosteroid Therapy
- name: Rituximab
  description: >-
    Anti-CD20 monoclonal antibody used for relapsing or refractory disease.
    Effective in inducing remission and reducing serum IgG4 levels by
    depleting B cell precursors of IgG4-producing plasma cells.
  treatment_term:
    preferred_term: rituximab therapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: rituximab
      term:
        id: NCIT:C1702
        label: Rituximab
- name: Inebilizumab
  description: >-
    Anti-CD19 monoclonal antibody evaluated in the Phase 3 MITIGATE trial
    (NCT04540497). CD19 targeting reaches a broader B-lineage window than
    anti-CD20 therapy, including plasmablast-biased disease biology.
  therapeutic_modality: MONOCLONAL_ANTIBODY
  target_mechanisms:
  - target: IgG4-Positive Plasmablast Expansion
    treatment_effect: INHIBITS
    description: >-
      Inebilizumab depletes CD19-positive B-lineage cells, linking clinical
      benefit to suppression of the plasmablast/B-cell axis modeled upstream of
      tissue plasma-cell infiltration and fibrosis.
    evidence:
    - reference: PMID:39541094
      reference_title: Inebilizumab for Treatment of IgG4-Related Disease.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Inebilizumab targets and depletes CD19+ B cells and may be effective
        for treating patients with IgG4-related disease.
      explanation: >-
        The Phase 3 trial describes CD19-positive B-cell depletion as the
        mechanism motivating inebilizumab in IgG4-RD.
  evidence:
  - reference: PMID:39541094
    reference_title: Inebilizumab for Treatment of IgG4-Related Disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Inebilizumab reduced the risk of flares of IgG4-related disease and
      increased the likelihood of flare-free complete remission at 1 year,
      confirming the role of CD19-targeted B-cell depletion as a potential
      treatment for IgG4-related disease.
    explanation: >-
      MITIGATE provides randomized Phase 3 evidence that CD19-targeted
      B-cell depletion reduces IgG4-RD flares.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: inebilizumab
      term:
        id: NCIT:C88283
        label: Inebilizumab
discussions:
- discussion_id: gap_igg4rd_dominant_autoantigen_identity
  prompt: >-
    What dominant autoantigen, antigen family, or antigen-presenting context
    initiates the coupled plasmablast and CD4-positive T-cell response in
    IgG4-RD?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Candidate Autoantigen Recognition and Antigen Presentation
  - pathophysiology#IgG4-Positive Plasmablast Expansion
  - pathophysiology#CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production
  rationale: >-
    The entry now models candidate autoantigen recognition upstream of both
    plasmablast expansion and fibrogenic CD4+ CTLs, but published candidate
    autoantigens explain only subsets. Resolving whether a dominant antigen, a
    per-organ antigen set, or bystander innate activation initiates the response
    would determine how specific the causal DAG should be.
  proposed_experiments:
  - experiment_id: exp_igg4rd_paired_bcr_tcr_antigen_discovery
    name: Paired BCR/TCR and autoantigen discovery across active IgG4-RD lesions
    description: >-
      From paired blood and affected-organ biopsies, sequence plasmablast BCRs
      and expanded CD4+ CTL TCRs, express dominant antibodies and TCRs, and test
      candidate antigens by proteome arrays, immunoprecipitation-mass
      spectrometry, and antigen-presentation assays.
    experiment_type:
      preferred_term: paired repertoire and antigen-discovery experiment
    model_systems:
    - name: Active human IgG4-RD blood and affected-organ biopsy pairs
      description: >-
        Prospective patient samples spanning pancreatobiliary, salivary/lacrimal,
        renal, retroperitoneal, and vascular IgG4-RD manifestations.
      experimental_model_type: OTHER
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
      cell_types:
      - preferred_term: plasmablast
        term:
          id: CL:0000980
          label: plasmablast
      - preferred_term: CD4-positive cytotoxic T lymphocyte
        term:
          id: CL:0000624
          label: CD4-positive, alpha-beta T cell
    readouts:
    - name: Shared and organ-restricted antigen specificity
      target: pathophysiology#Candidate Autoantigen Recognition and Antigen Presentation
      description: >-
        Concordance between dominant plasmablast antibody specificity, expanded
        lesional TCR recognition, and organ expression of candidate antigens.
      assays:
      - preferred_term: B cell receptor sequencing
      - preferred_term: T cell receptor sequencing
      - preferred_term: immunoprecipitation mass spectrometry
      direction: POSITIVE
    decision_criterion: >-
      A dominant autoantigen model is supported if recurrent antigen
      specificities are shared across independent patients and mechanistically
      connect plasmablast BCRs to lesional CD4+ T-cell activation; a per-organ
      model is supported if specificity tracks organ tropism instead.
    would_support:
    - pathophysiology#Candidate Autoantigen Recognition and Antigen Presentation
    - pathophysiology#IgG4-Positive Plasmablast Expansion
    - pathophysiology#CD4-Positive Cytotoxic T-Lymphocyte Fibrogenic Cytokine Production
  evidence:
  - reference: PMID:31612628
    reference_title: Disease Severity Linked to Increase in Autoantibody Diversity in IgG4-Related Disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      While these findings suggest an underlying importance for B cell tolerance
      and
      the potential pathogenicity of autoantibodies in IgG4-RD, they also
      highlight the unmet need in identifying a dominant and specific antigen
      that may drive the pathogenesis of IgG4-RD.
    explanation: >-
      The validation cohort explicitly frames dominant antigen identity as an
      unmet need despite several candidate autoantigens.
  - reference: PMID:24815737
    reference_title: De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      disease pathogenesis is linked to de novo recruitment of naive B cells
      into T cell-dependent responses by CD4(+) T cells, likely driving a
      self-reactive disease process.
    explanation: >-
      The B-cell repertoire study motivates a specific antigen-discovery gap
      connecting plasmablasts to CD4+ T-cell-dependent responses.
- discussion_id: gap_igg4rd_organ_tropism_and_fibroinflammation
  prompt: >-
    Why do shared plasmablast, IgG4 class-switching, and CD4-positive
    cytotoxic-T-cell programs produce different organ manifestations such as
    pancreatitis, cholangitis, retroperitoneal fibrosis, kidney disease, and
    salivary/lacrimal gland enlargement?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Storiform Fibrosis
  - pathophysiology#Organ-Specific Fibroinflammatory Injury
  rationale: >-
    IgG4-RD has a conserved fibroinflammatory histology, but the current model
    cannot yet explain why particular organs are targeted in individual
    patients. Organ-restricted antigens, epithelial-barrier functions,
    chemokine niches, and local stromal repair programs remain plausible but
    incompletely connected mechanisms.
  proposed_experiments:
  - experiment_id: exp_igg4rd_multi_organ_single_cell_stromal_immune_map
    name: Multi-organ single-cell immune-stromal map of IgG4-RD lesions
    description: >-
      Compare affected pancreas, bile duct, kidney, retroperitoneum, and
      salivary/lacrimal tissues using single-cell RNA sequencing, spatial
      transcriptomics, BCR/TCR sequencing, and autoantigen staining to separate
      shared fibroinflammatory circuitry from organ-specific injury programs.
    experiment_type:
      preferred_term: multi-organ single-cell spatial profiling study
    model_systems:
    - name: Human IgG4-RD affected-organ biopsy cohort
      description: >-
        Cross-organ biopsy cohort with matched blood, histopathology, serum
        autoantibody, and treatment-response metadata.
      experimental_model_type: OTHER
      organism:
        preferred_term: human
        term:
          id: NCBITaxon:9606
          label: Homo sapiens
    readouts:
    - name: Organ-specific antigen and stromal activation signatures
      target: pathophysiology#Organ-Specific Fibroinflammatory Injury
      description: >-
        Spatial colocalization of candidate autoantigens, plasmablasts/plasma
        cells, CD4+ CTLs, macrophages, fibroblasts, myofibroblasts, and
        extracellular matrix gene programs.
      assays:
      - preferred_term: single-cell RNA sequencing
      - preferred_term: spatial transcriptomics
      direction: POSITIVE
    decision_criterion: >-
      Organ tropism is supported as antigen/barrier-driven if candidate
      autoantigen expression and barrier injury localize with immune clonotypes
      and stromal activation in the affected organ more strongly than in
      unaffected or disease-control tissue.
    would_support:
    - pathophysiology#Organ-Specific Fibroinflammatory Injury
    - pathophysiology#Storiform Fibrosis
  evidence:
  - reference: PMID:38524667
    reference_title: Laminin 511-E8, an autoantigen in IgG4-related cholangitis, contributes to cholangiocyte protection.
    supports: PARTIAL
    evidence_source: IN_VITRO
    snippet: >-
      This makes it tempting to speculate that a decreased epithelial barrier
      function with attraction of immune cells and impaired bicarbonate
      secretion as a result of dysfunction of laminin 511 by autoantibody
      binding could potentially be a common systemic pathogenic mechanism in a
      subset of patients with IgG4-RD.
    explanation: >-
      Cholangitis data support a plausible epithelial-barrier mechanism, while
      the authors frame it as subset-level and still partly speculative.
  - reference: PMID:34718050
    reference_title: Role of the IgG4-related cholangitis autoantigen annexin A11 in cholangiocyte protection.
    supports: PARTIAL
    evidence_source: IN_VITRO
    snippet: >-
      Binding of patient-derived annexin A11 autoantibodies inhibits annexin
      A11 function, possibly contributing to bile duct damage by weakening the
      biliary bicarbonate umbrella in patients with IRC.
    explanation: >-
      Annexin A11 evidence supplies an organ-specific bile-duct injury model
      but does not explain non-biliary organ tropism.
datasets:
references:
- reference: DOI:10.1002/cti2.1477
  title: The spectrum of B cells in the pathogenesis, diagnosis and therapeutic applications of immunoglobulin <scp>G4</scp>‐related disease
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: Immunoglobulin G4 (IgG4)‐related disease is a chronic fibroinflammatory disease mediated by immune disorders.
    supporting_text: Immunoglobulin G4 (IgG4)‐related disease is a chronic fibroinflammatory disease mediated by immune disorders.
    evidence:
    - reference: DOI:10.1002/cti2.1477
      reference_title: The spectrum of B cells in the pathogenesis, diagnosis and therapeutic applications of immunoglobulin <scp>G4</scp>‐related disease
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Immunoglobulin G4 (IgG4)‐related disease is a chronic fibroinflammatory disease mediated by immune disorders.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.1016/j.ccm.2019.05.005
  title: Immunoglobulin G4–related Disease
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: Immunoglobulin G4–related Disease
    supporting_text: Immunoglobulin G4–related Disease
- reference: DOI:10.1093/rap/rkae020
  title: 'Current and future advances in practice: IgG4-related disease'
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: 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.
    supporting_text: 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.
    evidence:
    - reference: DOI:10.1093/rap/rkae020
      reference_title: 'Current and future advances in practice: IgG4-related disease'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: 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.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.1111/jgh.15809
  title: Nationwide epidemiological survey of immunoglobulin G4‐related disease with malignancy in Japan
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: Nationwide epidemiological survey of immunoglobulin G4‐related disease with malignancy in Japan
    supporting_text: and AimTo clarify the clinicoepidemiological characteristics of immunoglobulin G4 (IgG4)‐related disease (IgG4‐RD) with malignancy, a nationwide epidemiological survey was conducted.MethodsImmunoglobulin G4‐related disease patients with malignancy who had visited selected hospitals in Japan were surveyed.
    evidence:
    - reference: DOI:10.1111/jgh.15809
      reference_title: Nationwide epidemiological survey of immunoglobulin G4‐related disease with malignancy in Japan
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: and AimTo clarify the clinicoepidemiological characteristics of immunoglobulin G4 (IgG4)‐related disease (IgG4‐RD) with malignancy, a nationwide epidemiological survey was conducted.MethodsImmunoglobulin G4‐related disease patients with malignancy who had visited selected hospitals in Japan were surveyed.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.1111/resp.14422
  title: Thoracic manifestations of <scp>IgG4</scp>‐related disease
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year.
    supporting_text: Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year.
    evidence:
    - reference: DOI:10.1111/resp.14422
      reference_title: Thoracic manifestations of <scp>IgG4</scp>‐related disease
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.1136/annrheumdis-2018-214603
  title: 'Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts'
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: 'Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts'
    supporting_text: 'Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts'
- reference: DOI:10.1136/annrheumdis-2019-216561
  title: The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease
    supporting_text: The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease
- reference: DOI:10.1177/2050640620934911
  title: European Guideline on IgG4‐related digestive disease – UEG and SGF evidence‐based recommendations
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: The overall objective of these guidelines is to provide evidence‐based recommendations for the diagnosis and management of immunoglobulin G4 (IgG4)‐related digestive disease in adults and children.
    supporting_text: The overall objective of these guidelines is to provide evidence‐based recommendations for the diagnosis and management of immunoglobulin G4 (IgG4)‐related digestive disease in adults and children.
    evidence:
    - reference: DOI:10.1177/2050640620934911
      reference_title: European Guideline on IgG4‐related digestive disease – UEG and SGF evidence‐based recommendations
      supports: SUPPORT
      evidence_source: OTHER
      snippet: The overall objective of these guidelines is to provide evidence‐based recommendations for the diagnosis and management of immunoglobulin G4 (IgG4)‐related digestive disease in adults and children.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.1182/hematology.2024000584
  title: IgG4-related disease for the hematologist
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: Immunoglobulin G4–related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue.
    supporting_text: Immunoglobulin G4–related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue.
    evidence:
    - reference: DOI:10.1182/hematology.2024000584
      reference_title: IgG4-related disease for the hematologist
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: Immunoglobulin G4–related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.1186/s13023-014-0110-z
  title: 'IgG4- related disease: an orphan disease with many faces'
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: 'IgG4- related disease: an orphan disease with many faces'
    supporting_text: 'IgG4- related disease: an orphan disease with many faces'
- reference: DOI:10.12775/qs.2024.22.54293
  title: 'IgG4-Related Disease: Comprehensive Overview of Pathogenesis, Clinical Manifestations, and Diagnostic Challenges.'
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: IgG4-related disease (IgG4-RD) is a progressive and potentially life-threatening condition characterized by immune system activation and tissue fibrosis, affecting various organs such as the pancreas, kidneys, and lungs.
    supporting_text: IgG4-related disease (IgG4-RD) is a progressive and potentially life-threatening condition characterized by immune system activation and tissue fibrosis, affecting various organs such as the pancreas, kidneys, and lungs.
    evidence:
    - reference: DOI:10.12775/qs.2024.22.54293
      reference_title: 'IgG4-Related Disease: Comprehensive Overview of Pathogenesis, Clinical Manifestations, and Diagnostic Challenges.'
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: IgG4-related disease (IgG4-RD) is a progressive and potentially life-threatening condition characterized by immune system activation and tissue fibrosis, affecting various organs such as the pancreas, kidneys, and lungs.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.3389/fimmu.2024.1272084
  title: IgG4 autoantibodies and autoantigens in the context of IgG4-autoimmune disease and IgG4-related disease
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: Immunoglobulins are an essential part of the humoral immune response.
    supporting_text: Immunoglobulins are an essential part of the humoral immune response.
    evidence:
    - reference: DOI:10.3389/fimmu.2024.1272084
      reference_title: IgG4 autoantibodies and autoantigens in the context of IgG4-autoimmune disease and IgG4-related disease
      supports: SUPPORT
      evidence_source: OTHER
      snippet: Immunoglobulins are an essential part of the humoral immune response.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.
- reference: DOI:10.3389/fimmu.2024.1413860
  title: Pathogenic roles of follicular helper T cells in IgG4-related disease and implications for potential therapy
  found_in:
  - IgG4-Related_Disease-deep-research-falcon.md
  findings:
  - statement: IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems.
    supporting_text: IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems.
    evidence:
    - reference: DOI:10.3389/fimmu.2024.1413860
      reference_title: Pathogenic roles of follicular helper T cells in IgG4-related disease and implications for potential therapy
      supports: SUPPORT
      evidence_source: OTHER
      snippet: IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems.
      explanation: Deep research cited this publication as relevant literature for IgG4-Related Disease.

📚

References & Deep Research

References

DOI:10.1002/cti2.1477

The spectrum of B cells in the pathogenesis, diagnosis and therapeutic applications of immunoglobulin <scp>G4</scp>‐related disease

1 finding

Immunoglobulin G4 (IgG4)‐related disease is a chronic fibroinflammatory disease mediated by immune disorders.

"Immunoglobulin G4 (IgG4)‐related disease is a chronic fibroinflammatory disease mediated by immune disorders."

Show evidence (1 reference)

DOI:10.1002/cti2.1477 SUPPORT Human Clinical

"Immunoglobulin G4 (IgG4)‐related disease is a chronic fibroinflammatory disease mediated by immune disorders."

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.1016/j.ccm.2019.05.005

Immunoglobulin G4–related Disease

1 finding

Immunoglobulin G4–related Disease

"Immunoglobulin G4–related Disease"

DOI:10.1093/rap/rkae020

Current and future advances in practice: IgG4-related disease

1 finding

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.

"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."

Show evidence (1 reference)

DOI:10.1093/rap/rkae020 SUPPORT Human Clinical

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.1111/jgh.15809

Nationwide epidemiological survey of immunoglobulin G4‐related disease with malignancy in Japan

1 finding

Nationwide epidemiological survey of immunoglobulin G4‐related disease with malignancy in Japan

"and AimTo clarify the clinicoepidemiological characteristics of immunoglobulin G4 (IgG4)‐related disease (IgG4‐RD) with malignancy, a nationwide epidemiological survey was conducted.MethodsImmunoglobulin G4‐related disease patients with malignancy who had visited selected hospitals in Japan were..."

Show evidence (1 reference)

DOI:10.1111/jgh.15809 SUPPORT Human Clinical

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.1111/resp.14422

Thoracic manifestations of <scp>IgG4</scp>‐related disease

1 finding

Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year.

"Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year."

Show evidence (1 reference)

DOI:10.1111/resp.14422 SUPPORT Human Clinical

"Immunoglobulin G4‐related disease (IgG4‐RD) is a recently described rare systemic fibroinflammatory disease with an estimated incidence of less than 1 in 100,000 persons per year."

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.1136/annrheumdis-2018-214603

Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts

1 finding

Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts

"Clinical phenotypes of IgG4-related disease: an analysis of two international cross-sectional cohorts"

DOI:10.1136/annrheumdis-2019-216561

The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease

1 finding

The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease

"The 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-related disease"

DOI:10.1177/2050640620934911

European Guideline on IgG4‐related digestive disease – UEG and SGF evidence‐based recommendations

1 finding

The overall objective of these guidelines is to provide evidence‐based recommendations for the diagnosis and management of immunoglobulin G4 (IgG4)‐related digestive disease in adults and children.

"The overall objective of these guidelines is to provide evidence‐based recommendations for the diagnosis and management of immunoglobulin G4 (IgG4)‐related digestive disease in adults and children."

Show evidence (1 reference)

DOI:10.1177/2050640620934911 SUPPORT Other

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.1182/hematology.2024000584

IgG4-related disease for the hematologist

1 finding

Immunoglobulin G4–related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue.

"Immunoglobulin G4–related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue."

Show evidence (1 reference)

DOI:10.1182/hematology.2024000584 SUPPORT Human Clinical

"Immunoglobulin G4–related disease (IgG4-RD) is an immune-mediated disease with many important manifestations in hematopoietic and lymphoid tissue."

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.1186/s13023-014-0110-z

IgG4- related disease: an orphan disease with many faces

1 finding

IgG4- related disease: an orphan disease with many faces

"IgG4- related disease: an orphan disease with many faces"

DOI:10.12775/qs.2024.22.54293

IgG4-Related Disease: Comprehensive Overview of Pathogenesis, Clinical Manifestations, and Diagnostic Challenges.

1 finding

IgG4-related disease (IgG4-RD) is a progressive and potentially life-threatening condition characterized by immune system activation and tissue fibrosis, affecting various organs such as the pancreas, kidneys, and lungs.

"IgG4-related disease (IgG4-RD) is a progressive and potentially life-threatening condition characterized by immune system activation and tissue fibrosis, affecting various organs such as the pancreas, kidneys, and lungs."

Show evidence (1 reference)

DOI:10.12775/qs.2024.22.54293 SUPPORT Human Clinical

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.3389/fimmu.2024.1272084

IgG4 autoantibodies and autoantigens in the context of IgG4-autoimmune disease and IgG4-related disease

1 finding

Immunoglobulins are an essential part of the humoral immune response.

"Immunoglobulins are an essential part of the humoral immune response."

Show evidence (1 reference)

DOI:10.3389/fimmu.2024.1272084 SUPPORT Other

"Immunoglobulins are an essential part of the humoral immune response."

Deep research cited this publication as relevant literature for IgG4-Related Disease.

DOI:10.3389/fimmu.2024.1413860

Pathogenic roles of follicular helper T cells in IgG4-related disease and implications for potential therapy

1 finding

IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems.

"IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems."

Show evidence (1 reference)

DOI:10.3389/fimmu.2024.1413860 SUPPORT Other

"IgG4-related disease (IgG4-RD) is a recently described autoimmune disorder characterized by elevated serum IgG4 levels and tissue infiltration of IgG4+ plasma cells in multiple organ systems."

Deep research cited this publication as relevant literature for IgG4-Related Disease.

Deep Research

Falcon ▸

1. Disease Information

Edison Scientific Literature 34 citations 2026-05-09T09:36:38.889176

1. Disease Information

1.1 Concise overview (current understanding)

IgG4-related disease is a systemic, immune-mediated fibroinflammatory disorder that can produce tumefactive (mass-like) lesions in one or multiple organs and is unified by characteristic histopathology and clinicopathologic correlation (wallace2024currentandfuture pages 2-4, chen2024igg4relateddiseasefor pages 1-2). A core reason IgG4-RD is diagnostically challenging is that no single serologic test is both sensitive and specific, so biopsy and integrative assessment are central (wallace2024currentandfuture pages 2-4, bartoszek2024igg4relateddiseasecomprehensive pages 4-7).

Key diagnostic concept: tissue lesions typically show (i) dense lymphoplasmacytic infiltrate enriched for IgG4+ plasma cells, (ii) storiform fibrosis, and (iii) obliterative phlebitis, often with eosinophilia (chen2024igg4relateddiseasefor pages 1-2, wallace2024currentandfuture pages 2-4).

Direct abstract quote (identifier resource): Pieringer et al. state: “Immunoglobulin G4- related disease (IgG4-RD) is a rare systemic fibro-inflammatory disorder (ORPHA284264).” (pieringer2014igg4relateddisease pages 1-2)

1.2 Synonyms / alternative names

Commonly used alternative phrasings include “IgG4-related disease,” “IgG4-RD,” and organ-specific manifestations (e.g., type 1 autoimmune pancreatitis; IgG4-related sclerosing cholangitis; retroperitoneal fibrosis as a phenotype) (chen2024igg4relateddiseasefor pages 1-2, pieringer2014igg4relateddisease pages 2-4, wallace2024currentandfuture pages 2-4).

1.3 Evidence source type

The information below is derived primarily from aggregated disease-level resources (peer-reviewed reviews and guidelines) and from human cohort studies/registries and clinical trial registry records (wallace2024currentandfuture pages 2-4, wallace2020the2019american pages 1-1, wallace2024currentandfuture pages 1-2, NCT07148791 chunk 2).

2. Etiology

2.1 Disease causal factors (mechanistic)

The aetiology remains incompletely resolved, but convergent evidence indicates a B cell–T cell–driven immune disorder with downstream fibroinflammation (wallace2024currentandfuture pages 2-4, hao2023thespectrumof pages 2-4).

2.2 Risk factors

Genetic risk factors (susceptibility)

HLA associations have been reported in IgG4-RD and related phenotypes. Examples in the retrieved corpus include:
HLA-DRB1*03 association reported for retroperitoneal fibrosis (RPF) subtype (bartoszek2024igg4relateddiseasecomprehensive pages 4-7).
HLA-DR4 proposed susceptibility in autoimmune pancreatitis (AIP; an IgG4-RD manifestation) (wallace2019immunoglobuling4relateddisease. pages 1-2).
HLA-DRB1*16 and HLA-DQB1*05 described as “strongly associated” with autoimmune pancreatitis in one cohort (motta2024igg4autoantibodiesand pages 15-15).

Environmental / occupational risk factors

A Dutch study associated occupational exposure to solvents, oils, and industrial/metal dusts with IgG4-related cholangitis/pancreatitis (bartoszek2024igg4relateddiseasecomprehensive pages 4-7).
Smoking and asbestos exposure have been linked to retroperitoneal fibrosis risk (bartoszek2024igg4relateddiseasecomprehensive pages 4-7, wallace2019immunoglobuling4relateddisease. pages 1-2).

Infectious triggers

No unifying infectious trigger is established in the retrieved evidence; reviews emphasize the absence of a consistent infectious cause (bartoszek2024igg4relateddiseasecomprehensive pages 4-7, wallace2019immunoglobuling4relateddisease. pages 1-2).

2.3 Protective factors

No specific protective genetic or environmental factors were identified in the retrieved corpus.

2.4 Gene–environment interactions

Not clearly established in the retrieved corpus; current data support multifactorial susceptibility with organ-specific exposures and HLA background (bartoszek2024igg4relateddiseasecomprehensive pages 4-7, wallace2019immunoglobuling4relateddisease. pages 1-2).

3. Phenotypes (clinical manifestations)

3.1 Common organ involvement and clinical phenotypes

Contemporary clinical practice recognizes reproducible organ-pattern phenotypes, including: - Pancreato-hepatobiliary (type 1 autoimmune pancreatitis; sclerosing cholangitis) (wallace2024currentandfuture pages 2-4, chen2024igg4relateddiseasefor pages 1-2) - Retroperitoneum/aorta (retroperitoneal fibrosis; aortitis/large-vessel disease) (wallace2024currentandfuture pages 2-4, chen2024igg4relateddiseasefor pages 1-2) - Head-and-neck limited (salivary/lacrimal gland enlargement; orbital adnexal disease) (wallace2024currentandfuture pages 2-4) - Mikulicz/systemic (symmetric lacrimal/salivary enlargement plus systemic involvement; typically very high serum IgG4) (wallace2024currentandfuture pages 2-4)

Multi-organ involvement is common (reported as 60–90% in one review) (bartoszek2024igg4relateddiseasecomprehensive pages 4-7).

3.2 Frequencies and statistics from recent cohorts/surveys

In a large international cohort analysis, mean organ involvement was 2.9 organs (SD 1.8), serum IgG4 was elevated in 78.7%, and classic storiform fibrosis was reported in 39.6% (illustrating that classic histology is not always captured in routine reporting) (wallace2019clinicalphenotypesof pages 2-3).
In a Japanese nationwide survey focused on IgG4-RD with malignancy, organ frequencies included: autoimmune pancreatitis 44.7%, sialadenitis 20.8%, eye disease 14.0%, kidney disease 5.16%, retroperitoneal fibrosis 5.12% (sumimoto2022nationwideepidemiologicalsurvey pages 1-1).

3.3 Thoracic (lung/mediastinal) phenotype

Thoracic disease is clinically important and often incidental: - Up to 30% of systemic IgG4-RD patients may have thoracic involvement; thoracic disease is the sole manifestation in ~10% (muller2023thoracicmanifestationsof pages 1-2). - Reported estimates across cohorts are ~15–35% thoracic involvement (muller2023thoracicmanifestationsof pages 2-3).

3.4 Suggested HPO terms (examples; not exhaustive)

(These are ontology suggestions for knowledge-base encoding; mapping not directly cited in the retrieved literature.) - Tumefactive lesion / mass effect: HP:0002664 (Neoplasm) (used as proxy for mass-like lesion), HP:0033694 (Organomegaly) depending on organ. - Salivary/lacrimal enlargement: HP:0000217 (Xerostomia), HP:0001097 (Dry eyes), HP:0000175 (Parotid enlargement). - Obstructive jaundice (pancreatobiliary): HP:0000952 (Jaundice). - Retroperitoneal fibrosis-related obstruction: HP:0000795 (Ureteral obstruction). - Eosinophilia: HP:0001880 (Eosinophilia). - Hypergammaglobulinemia: HP:0012204 (Hypergammaglobulinemia).

4. Genetic / Molecular Information

4.1 Causal genes

IgG4-RD is not established as a monogenic disorder in the retrieved evidence. Genetic findings are primarily susceptibility associations (HLA and selected non-HLA loci) rather than causal variants (bartoszek2024igg4relateddiseasecomprehensive pages 4-7, motta2024igg4autoantibodiesand pages 15-15).

4.2 Pathogenic variants

No recurrent pathogenic germline variants defining IgG4-RD were identified in the retrieved corpus.

4.3 Autoantigens / autoantibodies (molecular targets)

Multiple candidate autoantigens have been reported in IgG4-RD. Examples include galectin-3 (reported in 28% of a cohort) and laminin-511 (detected in 50% of subjects with IgG4-related pancreatitis), supporting antigen-driven immunity in at least some patients (wallace2019immunoglobuling4relateddisease. pages 1-2).

5. Environmental Information

Environmental associations appear phenotype-specific: - Occupational exposure to solvents/oils/industrial & metal dusts has been associated with IgG4-related cholangitis/pancreatitis (bartoszek2024igg4relateddiseasecomprehensive pages 4-7). - Smoking and asbestos exposure have been linked to retroperitoneal fibrosis risk (bartoszek2024igg4relateddiseasecomprehensive pages 4-7, wallace2019immunoglobuling4relateddisease. pages 1-2).

No consistent infectious agent trigger is supported in the retrieved evidence (bartoszek2024igg4relateddiseasecomprehensive pages 4-7, wallace2019immunoglobuling4relateddisease. pages 1-2).

6. Mechanism / Pathophysiology (current model)

6.1 Core cellular players (with CL term suggestions)

Evidence converges on immune dysregulation involving: - B-lineage cells, especially plasmablasts (suggest CL:0000946 plasma cell; plasmablasts are a transitional phenotype). - T follicular helper (Tfh) cells (suggest CL:0000907 T follicular helper cell). - CD4+ cytotoxic T lymphocytes (CD4+ CTLs) (suggest CL:0000899 CD4-positive, alpha-beta T cell; “cytotoxic CD4” is a functional state).

6.2 B-cell/plasmablast axis and fibrosis linkage

Circulating plasmablasts are an important mechanistic and biomarker node: plasmablast levels correlate with serum IgG4, inflammatory markers, number of involved organs, and disease activity, and they fall with effective therapy and rise with relapse (hao2023thespectrumof pages 2-4, hao2023thespectrumof pages 4-6). A mechanistic link to fibrosis is proposed through plasmablast profibrotic programs (e.g., LOXL2 expression and PDGF-B secretion) (hao2023thespectrumof pages 2-4).

6.3 Tfh-driven class switching and plasmablast generation

Tfh cells provide B-cell help and promote IgG4 class-switching via IL-4/IL-21 and co-stimulatory interactions. Circulating PD-1+ Tfh measures correlate with serum IgG/IgG4 metrics and the number of organs involved (xu2024pathogenicrolesof pages 2-4). A 2024 review explicitly notes that “the expansion of circulating Tfh2 cells and plasmablasts may also serve as novel biomarkers for disease diagnosis and activity monitoring” (xu2024pathogenicrolesof pages 1-2).

6.4 CD4+ CTLs and profibrotic mediators

CD4+ CTLs infiltrate lesions and can produce profibrotic mediators such as TGF-β, providing a plausible bridge between immune activation and storiform fibrosis (hao2023thespectrumof pages 2-4).

6.5 Suggested GO biological process terms (examples)

(These are ontology suggestions; not directly asserted as GO annotations in the retrieved papers.) - GO:0006954 inflammatory response - GO:0042113 B cell activation - GO:0002460 adaptive immune response based on somatic recombination of immune receptors built from immunoglobulin superfamily domains - GO:0001525 angiogenesis / vascular remodeling (for obliterative phlebitis context) - GO:0042060 wound healing and GO:0006959 humoral immune response - GO:0045429 positive regulation of nitric oxide biosynthetic process (macrophage-related; hypothesis-level)

6.6 Suggested causal chain (integrated)

A plausible chain supported by current evidence is: antigen-driven or dysregulated immune activation → expansion of Tfh (especially Tfh2-like) and plasmablasts → IgG4 class switching and oligoclonal plasmablast expansion → recruitment/activation of profibrotic T-cell and myeloid programs (including CD4+ CTLs) → storiform fibrosis and organ dysfunction (hao2023thespectrumof pages 2-4, xu2024pathogenicrolesof pages 2-4, wallace2024currentandfuture pages 2-4).

7. Anatomical Structures Affected

7.1 Organs and systems (examples)

IgG4-RD can affect virtually any organ; commonly involved sites include pancreas and hepatobiliary system, salivary/lacrimal glands and orbit, retroperitoneum/aorta, kidney, lung/mediastinum, and lymph nodes (chen2024igg4relateddiseasefor pages 1-2, pieringer2014igg4relateddisease pages 2-4, wallace2024currentandfuture pages 2-4).

7.2 UBERON suggestions (examples)

Pancreas: UBERON:0001264
Lacrimal gland: UBERON:0001813
Major salivary gland: UBERON:0001044
Lung: UBERON:0002048
Kidney: UBERON:0002113
Retroperitoneum: UBERON:0003698

8. Temporal Development

8.1 Onset

IgG4-RD typically affects middle-aged to older adults (median around late 50s–60 in major cohorts) (chen2024igg4relateddiseasefor pages 1-2, muller2023thoracicmanifestationsof pages 2-3).

8.2 Course and progression

The disease often follows a relapsing–remitting course; if under-treated, it can cause irreversible fibrotic organ damage (wallace2024currentandfuture pages 2-4, chen2024igg4relateddiseasefor pages 1-2). Proliferative manifestations tend to respond better than chronic fibrotic disease, which may be less reversible (chen2024igg4relateddiseasefor pages 1-2).

9. Inheritance and Population

9.1 Epidemiology (recent estimates prioritized)

A 2024 practice review summarized a US claims-based analysis reporting: - Incidence: 0.78–1.39 per 100,000 person-years (2015–2019) - Point prevalence: 5.3 per 100,000 persons (as of 1 Jan 2019) (wallace2024currentandfuture pages 1-2)

A thoracic-manifestations review summarizes additional estimates, e.g., Japan incidence approximated at ~1 per 100,000 and prevalence ~0.8 per 100,000 (muller2023thoracicmanifestationsof pages 2-3), while also emphasizing heterogeneity.

9.2 Demographics

Male predominance is frequently reported overall, but varies by phenotype; head-and-neck–limited disease shows less male predominance (wallace2024currentandfuture pages 2-4, wallace2019clinicalphenotypesof pages 2-3).
In an international cohort, Asians had higher median serum IgG4 (median 666 vs 240.5 mg/dL in non-Asians), and males were older at onset/diagnosis than females (wallace2019clinicalphenotypesof pages 2-3).

10. Diagnostics

10.1 Histopathology and core features

Hallmark tissue features include dense lymphoplasmacytic infiltrate rich in IgG4+ plasma cells, storiform fibrosis, obliterative phlebitis, and eosinophilia. A common supportive threshold is an IgG4/IgG ratio >40% in tissue (chen2024igg4relateddiseasefor pages 1-2).

10.2 Classification criteria (2019 ACR/EULAR)

The 2019 ACR/EULAR criteria provide a validated, points-based framework requiring: entry organ involvement, exclusion criteria application, and weighted inclusion domains across clinical/serologic/radiologic/pathologic data, with classification at ≥20 points (wallace2020the2019american pages 1-1). Performance: - Derived/validated in 1,879 subjects (1,086 cases; 793 mimickers) (wallace2020the2019american pages 1-1) - Validation cohort 1: specificity 99.2%, sensitivity 85.5% at threshold 20 (wallace2020the2019american pages 1-1) - Validation cohort 2: specificity 97.8%, sensitivity 82.0% at threshold 20 (wallace2020the2019american pages 1-1)

10.3 Biomarkers

Serum IgG4 is often elevated and correlates with extent of organ involvement and relapse risk, but is not specific (wallace2024currentandfuture pages 2-4).
Circulating plasmablasts and Tfh-derived measures (e.g., PD-1+ cTfh metrics) are proposed activity biomarkers (hao2023thespectrumof pages 2-4, xu2024pathogenicrolesof pages 2-4).

10.4 Imaging and diagnostic pitfalls

Thoracic IgG4-RD has heterogeneous CT patterns and can mimic malignancy or vasculitis; cautious diagnosis includes searching for extra-thoracic disease and integrating serum IgG4/plasmablast measures plus pathology (muller2023thoracicmanifestationsof pages 1-2).

11. Outcome / Prognosis

11.1 Organ damage and reversibility

Clinical outcomes vary by phenotype: proliferative manifestations generally respond well to immunosuppression, whereas established fibrotic disease may be less reversible (chen2024igg4relateddiseasefor pages 1-2).

11.2 Malignancy association (statistics)

A Japanese nationwide survey reported an estimated overall prevalence of malignancy among IgG4-RD cases of ~10.9% (10,900 per 100,000 cases), and malignant lymphoma ~2.0% (1,985 per 100,000). IgG4-related kidney disease had the highest associated malignancy frequency (17.1%) (sumimoto2022nationwideepidemiologicalsurvey pages 1-1). These data are context-specific (survey methodology) and should be interpreted accordingly.

12. Treatment

12.1 Standard of care: glucocorticoids (real-world implementation)

European evidence-based guidance for IgG4-related digestive disease recommends: - Induction: oral glucocorticoids 0.6–0.8 mg/kg/day for 1 month (typical 30–40 mg/day prednisone equivalent) (lohr2020europeanguidelineon pages 17-19, lohr2020europeanguidelineon pages 1-2) - Response assessment: at week 2–4 using clinical/biochemical/morphological markers (lohr2020europeanguidelineon pages 17-19, lohr2020europeanguidelineon pages 1-2) - Taper: e.g., 5 mg every 2 weeks, over 3–6 months (lohr2020europeanguidelineon pages 17-19) - Relapse: common; guideline notes relapse rates 26–70% and high re-induction success with glucocorticoids (>95%) (lohr2020europeanguidelineon pages 19-20)

12.2 B-cell depletion and steroid-sparing therapy

B-cell depletion (rituximab) is widely used in relapsing/refractory disease and is supported by the central role of B cells/plasmablasts (hao2023thespectrumof pages 2-4, wallace2024currentandfuture pages 2-4).
A phase 1–2 registry trial entry exists for rituximab (NCT01584388) and cites a prospective open-label study publication (PMID: 25667206) (NCT01584388 chunk 2).

12.3 Emerging and investigational immunomodulators (clinical trials)

Belimumab (BAFF inhibition) RCT: NCT04660565 is described as an RCT of belimumab + glucocorticoids vs glucocorticoids alone, primary outcome relapse rate, 12-month follow-up (wallace2024currentandfuture pages 7-8). Registry: https://clinicaltrials.gov/study/NCT04660565 (post date and version dates vary by record).
Abatacept (CTLA4-Ig; co-stimulation blockade): NCT03669861 (Massachusetts General Hospital) (NCT03669861 chunk 2). Registry: https://clinicaltrials.gov/study/NCT03669861.
Anti-CD19/BCMA-CD19 CAR-T exploratory trial for relapsed/refractory IgG4-RD: NCT07148791, with key efficacy endpoint change in IgG4-RD Responder Index at baseline, week 12, week 26, and intensive safety monitoring for CRS/ICANS (NCT07148791 chunk 2). Registry: https://clinicaltrials.gov/study/NCT07148791.

Note: A placebo-controlled inebilizumab study is referenced in a 2024 table, but the excerpt available here is truncated and does not provide full registry detail (wallace2024currentandfuture pages 7-8).

12.4 MAXO term suggestions (examples)

Glucocorticoid therapy: MAXO:0000155 (glucocorticoid therapy)
B-cell depletion therapy (rituximab): MAXO:0001181 (B cell depletion therapy) (term may vary)
Abatacept therapy: MAXO: immunomodulatory therapy
Belimumab therapy: MAXO: monoclonal antibody therapy
CAR-T cell therapy: MAXO:0001503 (CAR T cell therapy)

13. Prevention

Primary prevention

No established primary prevention strategies are supported by the retrieved evidence.

Secondary/tertiary prevention (practical)

Early recognition and clinicopathologic confirmation (biopsy) are emphasized to avoid diagnostic delay and prevent irreversible fibrosis (wallace2024currentandfuture pages 2-4, bartoszek2024igg4relateddiseasecomprehensive pages 4-7).
Relapse prevention/monitoring: maintenance glucocorticoids may be considered in multi-organ disease or prior relapse; response monitoring at week 2–4; add immunosuppressives when relapse occurs early during taper or when disease is not controlled (lohr2020europeanguidelineon pages 1-2, lohr2020europeanguidelineon pages 19-20).

14. Other Species / Natural Disease

No evidence for naturally occurring IgG4-RD in non-human species was retrieved in this run.

15. Model Organisms

No standardized animal model systems were retrieved in the accessible corpus. A mouse immunization experiment linked to laminin-511 is mentioned as supporting an antigen-driven mechanism but details were not available in the retrieved text segments (wallace2019immunoglobuling4relateddisease. pages 1-2).

Key curated summary table

Category	Item	Summary	Publication	URL	Citation
Identifier	Orphanet ID	IgG4-related disease is identified as a rare systemic fibro-inflammatory disorder with Orphanet identifier ORPHA284264.	Pieringer et al., 2014	https://doi.org/10.1186/s13023-014-0110-z	(pieringer2014igg4relateddisease pages 1-2)
Defining histopathology	Lymphoplasmacytic infiltrate rich in IgG4+ plasma cells	Hallmark lesion includes a dense lymphoplasmacytic infiltrate enriched in IgG4-positive plasma cells; tissue diagnosis is essential.	Chen, 2024	https://doi.org/10.1182/hematology.2024000584	(chen2024igg4relateddiseasefor pages 1-2)
Defining histopathology	Storiform fibrosis	Storiform fibrosis is a core histopathologic feature and part of the classic triad used in diagnosis/classification.	Chen, 2024	https://doi.org/10.1182/hematology.2024000584	(chen2024igg4relateddiseasefor pages 1-2)
Defining histopathology	Obliterative phlebitis	Obliterative phlebitis is a characteristic histologic feature supporting IgG4-RD diagnosis.	Chen, 2024	https://doi.org/10.1182/hematology.2024000584	(chen2024igg4relateddiseasefor pages 1-2)
Supportive finding	Tissue eosinophilia	Tissue eosinophilia is a common supportive feature accompanying the histopathologic triad.	Chen, 2024	https://doi.org/10.1182/hematology.2024000584	(chen2024igg4relateddiseasefor pages 1-2)
Supportive finding	Serum IgG4 elevation	Many patients have elevated serum IgG4; this correlates with extent of organ involvement and relapse risk, but is not specific enough to diagnose disease alone.	Wallace et al., 2024	https://doi.org/10.1093/rap/rkae020	(wallace2024currentandfuture pages 2-4)
Supportive finding	Tissue IgG4/IgG ratio	A commonly used supportive tissue threshold is an IgG4:IgG plasma-cell ratio >40%.	Chen, 2024	https://doi.org/10.1182/hematology.2024000584	(chen2024igg4relateddiseasefor pages 1-2)
Classification criteria	2019 ACR/EULAR entry and threshold	Classification uses a 3-step process (typical organ involvement, exclusion criteria, weighted inclusion criteria) with a threshold of ≥20 points.	Wallace et al., 2020	https://doi.org/10.1136/annrheumdis-2019-216561	(wallace2020the2019american pages 1-1)
Classification performance	Cohort size used in development/validation	Criteria were developed/validated using 1,879 subjects total (1,086 cases and 793 mimickers).	Wallace et al., 2020	https://doi.org/10.1136/annrheumdis-2019-216561	(wallace2020the2019american pages 1-1)
Classification performance	Validation cohort 1	At ≥20 points, specificity was 99.2% (95% CI 97.2–99.8) and sensitivity was 85.5% (95% CI 81.9–88.5).	Wallace et al., 2020	https://doi.org/10.1136/annrheumdis-2019-216561	(wallace2020the2019american pages 1-1)
Classification performance	Validation cohort 2	At ≥20 points, specificity was 97.8% (95% CI 93.7–99.2) and sensitivity was 82.0% (95% CI 77.0–86.1).	Wallace et al., 2020	https://doi.org/10.1136/annrheumdis-2019-216561	(wallace2020the2019american pages 1-1)

Table: This table summarizes the core disease identifier, defining pathology, supportive findings, and validated 2019 ACR/EULAR classification performance for IgG4-related disease. It is useful as a compact reference for knowledge-base curation and diagnostic context.

Notes on evidence gaps and limitations

Ontology identifiers (MONDO, MeSH, ICD) were not retrievable from the current tool-accessible literature corpus; the report therefore does not assert them.
Several important 2023–2025 primary studies (e.g., single-cell transcriptomics; some therapeutics RCT publications) were listed as unobtainable in tool retrieval; mechanistic and treatment sections thus emphasize accessible, high-quality reviews/cohorts and clinical trial registry records.
HPO/GO/UBERON/MAXO terms are provided as suggestions for encoding and were not directly mapped in the cited papers.

References

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(lohr2020europeanguidelineon pages 19-20): J‐Matthias Löhr, Ulrich Beuers, Miroslav Vujasinovic, Domenico Alvaro, Jens Brøndum Frøkjær, Frank Buttgereit, Gabriele Capurso, Emma L Culver, Enrique de‐Madaria, Emanuel Della‐Torre, Sönke Detlefsen, Enrique Dominguez‐Muñoz, Piotr Czubkowski, Nils Ewald, Luca Frulloni, Natalya Gubergrits, Deniz Guney Duman, Thilo Hackert, Julio Iglesias‐Garcia, Nikolaos Kartalis, Andrea Laghi, Frank Lammert, Fredrik Lindgren, Alexey Okhlobystin, Grzegorz Oracz, Andrea Parniczky, Raffaella Maria Pozzi Mucelli, Vinciane Rebours, Jonas Rosendahl, Nicolas Schleinitz, Alexander Schneider, Eric FH van Bommel, Caroline Sophie Verbeke, Marie Pierre Vullierme, and Heiko Witt. European guideline on igg4‐related digestive disease – ueg and sgf evidence‐based recommendations. United European Gastroenterology Journal, 8:637-666, Jul 2020. URL: https://doi.org/10.1177/2050640620934911, doi:10.1177/2050640620934911. This article has 272 citations and is from a peer-reviewed journal.
(NCT01584388 chunk 2): John H. Stone, MD. Rituximab in IgG4-RD: A Phase 1-2 Trial. Massachusetts General Hospital. 2012. ClinicalTrials.gov Identifier: NCT01584388
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OpenScientist Report

Subtypes

Mechanistic Hypotheses

Discussions and Knowledge Gaps

Pathophysiology

Histopathology

Pathograph

Phenotypes

Medical Actions

Biochemical Markers

Source YAML

References & Deep Research

References

Deep Research

1. Disease Information

1.1 Concise overview (current understanding)

1.2 Synonyms / alternative names

1.3 Evidence source type

2. Etiology

2.1 Disease causal factors (mechanistic)

2.2 Risk factors

Genetic risk factors (susceptibility)

Environmental / occupational risk factors

Infectious triggers

2.3 Protective factors

2.4 Gene–environment interactions

3. Phenotypes (clinical manifestations)

3.1 Common organ involvement and clinical phenotypes

3.2 Frequencies and statistics from recent cohorts/surveys

3.3 Thoracic (lung/mediastinal) phenotype

3.4 Suggested HPO terms (examples; not exhaustive)

4. Genetic / Molecular Information

4.1 Causal genes

4.2 Pathogenic variants

4.3 Autoantigens / autoantibodies (molecular targets)

5. Environmental Information

6. Mechanism / Pathophysiology (current model)

6.1 Core cellular players (with CL term suggestions)

6.2 B-cell/plasmablast axis and fibrosis linkage

6.3 Tfh-driven class switching and plasmablast generation

6.4 CD4+ CTLs and profibrotic mediators

6.5 Suggested GO biological process terms (examples)

6.6 Suggested causal chain (integrated)

7. Anatomical Structures Affected

7.1 Organs and systems (examples)

7.2 UBERON suggestions (examples)

8. Temporal Development

8.1 Onset

8.2 Course and progression

9. Inheritance and Population

9.1 Epidemiology (recent estimates prioritized)

9.2 Demographics

10. Diagnostics

10.1 Histopathology and core features

10.2 Classification criteria (2019 ACR/EULAR)

10.3 Biomarkers

10.4 Imaging and diagnostic pitfalls

11. Outcome / Prognosis

11.1 Organ damage and reversibility

11.2 Malignancy association (statistics)

12. Treatment

12.1 Standard of care: glucocorticoids (real-world implementation)

12.2 B-cell depletion and steroid-sparing therapy

12.3 Emerging and investigational immunomodulators (clinical trials)

12.4 MAXO term suggestions (examples)

13. Prevention

Primary prevention

Secondary/tertiary prevention (practical)

14. Other Species / Natural Disease

15. Model Organisms

Key curated summary table

Notes on evidence gaps and limitations