🏷

Classifications

Harrison's Chapter

👪

Inheritance

1

Polygenic inheritance HP:0010982

Complex, non-Mendelian autoimmune disease with polygenic susceptibility - HLA-DQB1 plus non-HLA loci (PTPN22, IL2RA) shared with other organ-specific autoimmune diseases - acting together with environmental factors.

Polygenic inheritance

Show evidence (1 reference)

PMID:34145262 SUPPORT Human Clinical

"We conduct a genome-wide association study meta-analysis in 2166 cases and 659,516 European controls from population-based biobanks and identify genome-wide significant signals in or near the PTPN22"

A GWAS identifies multiple risk loci (PTPN22, HLA-DQB1, IL2RA) for pernicious anemia / autoimmune gastritis, establishing polygenic inheritance.

C

Comorbidities

Autoimmune Gastritis <-> Hashimotos Thyroiditis

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Mechanistic Hypotheses

4

Canonical Primary Autoimmunity Against the Gastric H+/K+ ATPase

canonical_primary_autoimmune_hk_atpase_origin CANONICAL

Autoimmune gastritis is a primary organ-specific autoimmune disease driven by a breakdown of self-tolerance to the parietal-cell H+/K+ ATPase (ATP4A/ATP4B), with CD4 T-cell-mediated parietal cell destruction that is self-sustaining. The tolerance defect implicates the beta subunit: although H/K-ATPase alpha-subunit (ATP4A) mRNA is expressed in the thymus, thymic expression alone does not tolerize the pathogenic T-cell repertoire, and it is the beta subunit (ATP4B), absent from the thymus, that behaves as the dominant autoantigen. The murine disease induced by neonatal thymectomy is T-cell-mediated, and monogenic tolerance defects (AIRE/APECED, FOXP3/IPEX) produce autoimmune gastritis as part of polyautoimmunity. Two independent hypothesis-search runs (see notes) concur that this primary/central-tolerance account is best treated as one of several parallel initiating pathways feeding a shared effector cascade, rather than as an infection-independent sole origin.

Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED: a claude_code report (kb/hypotheses/Autoimmune_Gastritis/canonical_primary_autoimmune_hk_atpase_origin/claude_code.md) and a deeper openscientist report (same directory, openscientist.md; 127 papers, 17 findings over 5 iterations). Both retain the CD4 T-cell / H+/K+ ATPase effector mechanism as CANONICAL but judge the etiological claim of a purely primary, infection-independent origin overstated: the disease is best modeled as multiple parallel initiating pathways - primary central-tolerance defect, H. pylori molecular mimicry (T-cell level; see alternative_hpylori_molecular_mimicry_origin), neonatal roseolovirus thymic disruption, and peripheral checkpoint failure (anti-PD-1/anti-CTLA-4 gastritis) - all converging on the same self-sustaining effector cascade. The ATP4A/ATP4B tolerance correction flagged by both runs (alpha thymic expression does not tolerize; ATP4B is the thymus-absent dominant autoantigen) has been folded into the description above (PMID:16237067). Follow-up recommended by openscientist: split into separate CANONICAL effector and qualified etiological-trigger hypotheses, and add an upstream "incomplete central tolerance to ATP4B" node.

Deep research

Claude Code 2026-07-01T08:02:42.111955

OpenScientist citations 37 citations 2026-07-01T14:50:02.872849

Show evidence (2 references)

PMID:9272282 SUPPORT Model Organism

"The murine disease induced by neonatal thymectomy is T cell-mediated."

The T-cell-mediated neonatal-thymectomy model supports a T-cell-driven autoimmune origin of gastritis.

PMID:16237067 PARTIAL Model Organism

"thymic mRNA expression alone cannot predict a contribution to thymic tolerance."

Corrects the tolerance framing - thymic H/K-ATPase alpha-subunit mRNA expression does not negatively select pathogenic T cells, so central tolerance to the alpha subunit is not protective; the beta subunit (absent from the thymus) is the dominant autoantigen.

Alternative H. pylori Molecular-Mimicry ("Hit-and-Run") Origin

alternative_hpylori_molecular_mimicry_origin ALTERNATIVE

Autoimmune gastritis is initiated by Helicobacter pylori infection via molecular mimicry between H. pylori antigens and the gastric H+/K+ ATPase, generating cross-reactive T- and B-cell responses that, through epitope spreading and bystander activation in a genetically susceptible host, become self-perpetuating autoimmunity and persist after the organism is cleared (established AIG is frequently H. pylori-negative). A corollary is that a subset of cases are reversible with early eradication. Causation in humans remains unproven and is the basis of a knowledge-gap discussion.

Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED / UNRESOLVED: a claude_code report (kb/hypotheses/Autoimmune_Gastritis/alternative_hpylori_molecular_mimicry_origin/claude_code.md) and a deeper openscientist report (same directory, openscientist.md). H. pylori- to-H+/K+ ATPase cross-reactivity is documented at the T-cell level (cross-reactive gastric CD4 Th1 clones; urease beta-subunit homology; LPS Lewis-antigen mimicry), and early-stage non-atrophic AIG is reported to heal after eradication in ~80% of cases (supporting a time-limited "hit-and-run" window). However the model is causally unproven and non-general: molecular mimicry is refuted at the autoantibody level (antigastric autoantibodies do not absorb to H. pylori; Faller), a large fraction of AIG patients (~29-79%) are H. pylori-naive and form a distinct familial/autoimmune-enriched entity (ARIOSO n=1,598; PMID:38976374), Treg-depletion mouse models produce AIG with no infection, and some H. pylori-AIG associations may be inflated by diagnostic misclassification (urease-positive non-H. pylori bacteria overgrowing the achlorhydric stomach). Retained ALTERNATIVE, best read as a subset-initiation mechanism.

Deep research

Claude Code 2026-07-01T14:13:03.864853

OpenScientist citations 35 citations 2026-07-01T15:00:08.716366

Show evidence (3 references)

PMID:21174235 SUPPORT Human Clinical

"a role for Helicobacter pylori as an infective trigger through molecular mimicry"

States H. pylori as a candidate infective trigger of autoimmune gastritis via molecular mimicry.

PMID:42254085 PARTIAL Human Clinical

"Rapid eradication of H. pylori can significantly improve hematologic parameters and prevent the progression of autoimmune gastritis."

A reversible, H. pylori-attributable presentation is consistent with an infection-triggered origin in a subset of cases.

PMID:38976374 PARTIAL Human Clinical

"H. pylori -naive patients were more likely to have a first-degree family history of AIG (14.7% vs 8.9%; P = 0.012), type 1 diabetes mellitus (4.9% vs 2.3%; P = 0.025), and pernicious anemia (30.9% vs 21.1%; P = 0.003)."

The largest AIG cohort (n=1,598) identifies H. pylori-naive AIG as a distinct entity with stronger familial/autoimmune signatures, limiting the mimicry hypothesis to a subset rather than a general etiology.

Canonical Th1/IFN-gamma Effector Polarization

canonical_th1_effector_polarization CANONICAL

The effector arm driving parietal-cell destruction has classically been modeled as Th1/IFN-gamma-polarized, based on murine neonatal-thymectomy and TCR-transgenic effector-transfer systems specific for the H+/K+ ATPase.

Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED: a claude_code report (kb/hypotheses/Autoimmune_Gastritis/canonical_th1_effector_polarization/claude_code.md) and an openscientist report (same directory, openscientist.md). Both retain Th1/IFN-gamma as foundational and real (anti-IFN-gamma blockade prevents murine disease; human gastric H+/K+ ATPase-reactive CD4 clones are predominantly Th1 and cytotoxic via perforin/Fas-FasL; IFN-gamma directly kills gastric epithelium in organoids; the PTPN22 pernicious-anemia risk variant favors Th1 over Th17), but neither supports a Th1-exclusive model - it is one arm of a cooperative multi-cytokine / multi-cell-type program: CD8 T cells are the dominant IFN-gamma source, IFN-gamma plus IL-17 are co-required for severe disease (PMID:22777705), IL-13 independently drives the post-atrophy metaplastic transformation, and the human intrinsic-factor-reactive / pernicious-anemia compartment is Th17-dominant (see emerging_th17_effector_polarization). Caveat: Th1 dominance is demonstrated most robustly in TCR-transgenic / monoclonal systems, which may overrepresent it relative to polyclonal disease.

Pathograph links

CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump -> Parietal Cell Destruction and Oxyntic Atrophy Autoreactive CD4+ T cells and autoantibodies drive parietal cell apoptosis and loss.

Deep research

Claude Code citations 12 citations 2026-07-01T08:03:18.729534

OpenScientist citations 22 citations 2026-07-01T16:48:20.055197

Show evidence (3 references)

PMID:18641328 SUPPORT Model Organism

"We have evaluated the capacity of fully differentiated Th1, Th2, and Th17 cells derived from a mouse bearing a transgenic TCR specific for the gastric parietal cell antigen, H(+)K(+)-ATPase, to induce autoimmune gastritis after transfer to immunodeficient recipients."

Effector-transfer model in which Th1 (among other subsets) specific for the H+/K+ ATPase induces autoimmune gastritis.

PMID:15763992 SUPPORT Human Clinical

"The majority of the autoreactive T cell clones secreted IFN-gamma and showed a T helper 1 (Th1) profile."

Human gastric H+/K+ ATPase-reactive CD4 clones are predominantly Th1 (IFN-gamma) and cytotoxic, directly supporting the Th1 effector arm in human disease.

PMID:22777705 PARTIAL Model Organism

"both are required for the disease to progress to the late pathogenic stage that includes significant tissue disruption."

IFN-gamma and IL-17 are co-required for severe disease (and CD8 T cells are the dominant IFN-gamma source), qualifying a Th1-exclusive model.

Emerging Th17/IL-17 Effector Contribution

emerging_th17_effector_polarization EMERGING

Human data show a gastric H+/K+ ATPase-specific Th17/IL-17 signature, and effector-transfer models show that Th1, Th2, and Th17 cells can each induce autoimmune gastritis with distinct pathology and differing susceptibility to regulatory T-cell suppression. Which effector arm dominates human disease, and whether it shifts over the disease course, is unresolved and carries therapeutic implications (e.g., anti-IL-17 blockade).

Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED / retain EMERGING: a claude_code report (kb/hypotheses/Autoimmune_Gastritis/emerging_th17_effector_polarization/claude_code.md) and an openscientist report (same directory, openscientist.md). Both confirm a genuine Th17/IL-17 contribution (H+/K+ ATPase-specific gastric IL-17A/F production; 94% of intrinsic-factor-reactive clones Th17/Th1; Th17 transfer gives the most severe, Treg-resistant gastritis in the TxA23 model), but the openscientist run corrects the effector mechanism: IL-17RA signaling on gastric epithelium appears PROTECTIVE rather than directly apoptotic (IL-17RA loss increases B-cell infiltration, autoantibody production, and inflammation, and accelerates gastric carcinogenesis), so the pathogenic Th17-derived signal is more likely IL-21 and STAT3-mediated (STAT3 inhibition restores Th17/Treg balance and alleviates disease; PMID:40471463) than IL-17A/F epithelial cytotoxicity. Consequently anti-IL-17 blockade is cautioned/contraindicated (protective, anti-carcinogenic IL-17), no human anti-IL-17 AIG data exist, Th1 remains the more extensively validated axis, and which arm dominates by disease stage is unresolved. Reframe: Th17 contributes via IL-21/STAT3, not direct IL-17A/F epithelial killing.

Pathograph links

CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump -> Parietal Cell Destruction and Oxyntic Atrophy Autoreactive CD4+ T cells and autoantibodies drive parietal cell apoptosis and loss.

Deep research

Claude Code citations 10 citations 2026-07-01T14:13:13.539858

OpenScientist citations 24 citations 2026-07-01T16:33:30.602581

Show evidence (4 references)

PMID:35911678 SUPPORT Human Clinical

"Gastric LPMCs from all AIG patients, but not those from HCs, were activated by H+/K+-ATPase and were able to proliferate and produce high levels of IL-17A and IL-17F."

Human gastric T cells produce IL-17A/IL-17F on H+/K+ ATPase stimulation, evidencing a Th17 effector contribution.

PMID:18641328 SUPPORT Model Organism

"We have evaluated the capacity of fully differentiated Th1, Th2, and Th17 cells derived from a mouse bearing a transgenic TCR specific for the gastric parietal cell antigen, H(+)K(+)-ATPase, to induce autoimmune gastritis after transfer to immunodeficient recipients."

Th17 effector cells can independently induce autoimmune gastritis in the transfer model, supporting an emerging Th17 arm.

PMID:31080562 SUPPORT Human Clinical

"Most of these clones (94%) showed a T helper 17 or T helper 1 profile."

In pernicious anemia, intrinsic-factor-specific gastric CD4 clones are predominantly Th17/Th1 (Th17-skewed), evidencing a Th17 contribution in the intrinsic-factor-reactive compartment.

+ 1 more reference

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Discussions and Knowledge Gaps

4

Do murine autoimmune-gastritis models (neonatal thymectomy, H+/K+ ATPase immunization, and TCR-transgenic effector-transfer systems) faithfully reproduce human autoimmune gastritis, or do they capture only the initiation and parietal-cell-destruction biology while failing to model the human-specific downstream trajectory of chronic ECL-cell hyperplasia progressing to type 1 gastric neuroendocrine tumors, long-term gastric adenocarcinoma risk, and polyautoimmune clustering (thyroid, type 1 diabetes, vitiligo)?

HUMAN MODEL MISMATCH OPEN hmm_aig_mouse_model_neoplastic_trajectory

Attached to

pathophysiology#CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump pathophysiology#Hypergastrinemia and ECL Cell Hyperplasia

Mouse models robustly recapitulate the core autoantigen (H+/K+ ATPase), the CD4 T-cell-mediated destructive mechanism, and atrophic/metaplastic histology, and they are the primary source of mechanistic detail (effector-subset pathogenicity and Treg-dependent tolerance). However, short-lived rodent models less consistently reproduce the chronic hypergastrinemia -> ECL hyperplasia -> type 1 gastric NET sequence and the decades-long adenocarcinoma risk that dominate human clinical management, and single-antigen mouse systems do not intrinsically model human polyautoimmune comorbidity. Consequently the neoplastic-complication arm of the human entry rests on human observational data rather than on validated model mechanism.

Proposed experiments

Longitudinal ECL-to-NET progression in a chronic hypergastrinemic AIG model

exp_aig_longterm_ecl_neoplasia

In a chronic autoimmune-gastritis model with sustained achlorhydria and hypergastrinemia, longitudinally quantify the ECL-cell hyperplasia -> dysplasia -> type 1 gastric NET sequence and adenocarcinoma incidence over extended timeframes, mapped onto human histologic staging.

Model systems

Chronic murine autoimmune gastritis model

Long-lived mouse model with sustained achlorhydria and hypergastrinemia (e.g., effector-transfer or gastrin-clamped systems) followed for ECL-cell neoplastic progression.

OTHER

Decision criterion

Whether comparable degrees and durations of hypergastrinemia reproduce the human ECL-to-NET-to-adenocarcinoma sequence.

Would support

Faithful reproduction would validate the human neoplastic trajectory as a direct consequence of the modeled autoimmune-achlorhydria-hypergastrinemia axis.

Would refute

Failure to progress despite equivalent hypergastrinemia would indicate human-specific ECL/gastric-epithelial biology not captured by rodent models.

What initiates the loss of tolerance in the common sporadic (polygenic) form of autoimmune gastritis? H. pylori molecular mimicry is the leading trigger hypothesis, but established disease is usually H. pylori-negative and human causation is unproven; other triggers (viral, unidentified) and the gene-environment "second-hit" model (a PTPN22/HLA/AIRE background lowering the threshold for infection-triggered mimicry and epitope spreading) remain unvalidated in humans.

KNOWLEDGE GAP OPEN gap_aig_sporadic_tolerance_trigger

Attached to

pathophysiology#CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump

The trigger question directly gates the two competing origin hypotheses (primary autoimmunity vs. H. pylori mimicry) and determines whether a modifiable environmental exposure exists. It cannot be resolved by the current snippet-supported human associations, which are cross-sectional and confounded by the frequent absence of the organism at diagnosis.

Is the autoimmune process still active and pharmacologically targetable at the time of diagnosis, or is it effectively "burnt out"? There is no disease-modifying therapy for autoimmune gastritis - management is micronutrient replacement and surveillance - and it is unknown whether early immunomodulation (regulatory T-cell restoration or Th17/IL-17 blockade) could halt progression to atrophy, pernicious anemia, and neoplasia.

KNOWLEDGE GAP OPEN gap_aig_disease_modifying_therapy_active_window

Attached to

pathophysiology#CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump

Whether the effector response persists at a targetable level once corpus atrophy is established determines if immunomodulatory therapy is even mechanistically plausible; the emerging Th17 arm makes anti-IL-17 blockade a concrete but untested candidate.

What is the natural history and timeline of autoimmune gastritis from the earliest seropositive ("potential AIG") phase through corpus atrophy, pernicious anemia, and neoplastic complications, and what distinguishes the poorly-studied pediatric-onset subgroup?

KNOWLEDGE GAP OPEN gap_aig_natural_history_pediatric

Attached to

pathophysiology#Parietal Cell Destruction and Oxyntic Atrophy

The pre-atrophic seropositive phase is the clinically actionable window for early detection, but the rate and determinants of progression to irreversible atrophy and to neoplasia are not established prospectively, and the pediatric-onset subgroup's long-term course is largely unstudied.

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Pathophysiology

4

CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump

The central pathogenic event is a CD4+ T helper (Th1/Th17)-polarized autoimmune response directed against the alpha (ATP4A) and beta (ATP4B) subunits of the gastric H+/K+ ATPase expressed by parietal cells. Autoreactive T cells and parietal cell autoantibodies target the oxyntic mucosa of the gastric corpus and fundus, sparing the antrum. Molecular mimicry with Helicobacter pylori antigens has been proposed as an initiating trigger.

Canonical Th1/IFN-gamma Effector Polarization Emerging Th17/IL-17 Effector Contribution

CD4+ T helper cell CL:0000492 ↑ INCREASED parietal cell CL:0000162 ↓ DECREASED

adaptive immune response against the H+/K+ ATPase GO:0002250 ↑ INCREASED parietal cell apoptosis GO:0006915 ↑ INCREASED

Downstream

Parietal Cell Destruction and Oxyntic Atrophy Autoreactive CD4+ T cells and autoantibodies drive parietal cell apoptosis and loss.

Show evidence (4 references)

PMID:35911678 SUPPORT Human Clinical

"The gastric parietal cell proton pump H+/K+-adenosine triphosphatase (H+/K+-ATPase) is the major autoantigen in AIG."

Identifies the gastric H+/K+ ATPase as the principal autoantigen targeted in autoimmune gastritis.

PMID:35911678 SUPPORT Human Clinical

"Gastric LPMCs from all AIG patients, but not those from HCs, were activated by H+/K+-ATPase and were able to proliferate and produce high levels of IL-17A and IL-17F."

Demonstrates antigen-specific gastric T cell activation and proliferation in response to the H+/K+ ATPase autoantigen in AIG patients.

PMID:42367768 SUPPORT Human Clinical

"Autoimmune gastritis (AIG) is a chronic, organ-specific autoimmune disease characterized by the immune-mediated destruction of gastric parietal cells, leading to impaired acid secretion, vitamin B12 deficiency, and an increased risk of gastric malignancies."

Establishes immune-mediated parietal cell destruction as the central pathogenic mechanism of autoimmune gastritis.

+ 1 more reference

Parietal Cell Destruction and Oxyntic Atrophy

Immune-mediated destruction of parietal cells leads to progressive atrophy of the oxyntic (acid-secreting) mucosa restricted to the corpus and fundus. Loss of parietal cells abolishes both gastric acid and intrinsic factor secretion, and the mucosa undergoes pseudopyloric and intestinal metaplasia.

parietal cell CL:0000162 ∅ ABSENT

gastric acid secretion GO:0001696 ↓ DECREASED

Downstream

Atrophic Gastritis Progressive parietal cell loss produces corpus-restricted atrophic gastritis.

Achlorhydria Parietal cell loss abolishes gastric acid secretion.

Iron Deficiency Anemia Loss of gastric acid impairs acid-dependent dietary iron absorption, causing iron deficiency anemia.

Intrinsic Factor Deficiency and B12 Malabsorption Parietal cell loss abolishes intrinsic factor secretion.

Hypergastrinemia and ECL Cell Hyperplasia Loss of luminal acid removes negative feedback on antral gastrin release.

Gastric Adenocarcinoma Oxyntic atrophy with intestinal metaplasia forms a precancerous field predisposing to intestinal-type gastric adenocarcinoma.

Show evidence (1 reference)

PMID:28102858 SUPPORT Human Clinical

"Atrophic body gastritis (AGB) is the pathological lesion of autoimmune gastritis, characterized by the disappearance of oxyntic mucosa"

Confirms that parietal-cell destruction produces corpus-restricted disappearance of the oxyntic mucosa (atrophic body gastritis).

Intrinsic Factor Deficiency and B12 Malabsorption

Loss of intrinsic factor (encoded by CBLIF/GIF) secreted by parietal cells, compounded by anti-intrinsic factor autoantibodies, prevents ileal absorption of dietary vitamin B12 (cobalamin), causing systemic cobalamin deficiency and pernicious anemia.

parietal cell CL:0000162 ∅ ABSENT

Downstream

Pernicious Anemia Cobalamin deficiency impairs erythropoiesis, causing megaloblastic anemia.

Peripheral Neuropathy Cobalamin deficiency causes neurological injury including subacute combined degeneration.

Glossitis Cobalamin deficiency causes atrophic glossitis.

Show evidence (2 references)

PMID:31080562 SUPPORT Human Clinical

"The intrinsic factor is the major humoral autoantigen in pernicious anemia/autoimmune gastritis."

Establishes intrinsic factor as the major humoral autoantigen whose loss (and autoantibody targeting) causes the B12 malabsorption of pernicious anemia.

PMID:21174235 SUPPORT Human Clinical

"megaloblastic pernicious anemia arising from vitamin B12 deficiency"

Links the intrinsic-factor-dependent vitamin B12 deficiency to megaloblastic pernicious anemia.

Hypergastrinemia and ECL Cell Hyperplasia

Achlorhydria removes the acid-mediated negative feedback on antral G cells, producing marked hypergastrinemia. Chronically elevated gastrin is trophic for enterochromaffin-like (ECL) cells in the corpus, driving ECL cell hyperplasia that can progress through dysplasia to type 1 gastric neuroendocrine tumors.

antral G cell CL:0000508 ↑ INCREASED enterochromaffin-like cell CL:0000504 ↑ INCREASED

Downstream

Hypergastrinemia Achlorhydria-driven loss of feedback on antral G cells produces marked hypergastrinemia.

Gastric Neuroendocrine Tumor Sustained gastrin drive promotes ECL hyperplasia to neoplasia.

Show evidence (2 references)

PMID:31963924 SUPPORT Human Clinical

"tumorigenesis is mediated by gastrin's effects on the CCK2R-receptor on ECL-cells that in turn leads to hyperplasia, dysplasia, and finally neoplasia"

Describes the gastrin-CCK2R trophic pathway by which chronic hypergastrinemia drives ECL cell hyperplasia, dysplasia, and neoplasia.

PMID:34476276 SUPPORT Human Clinical

"This leads to the absence of gastric acid production, which causes compensatory hyperplasia of gastric antral G-cells leading to hypergastrinemia. The excess gastrin binds to enterochromaffin-like cells causing hyperplasia, which may progress to dysplasia and rarely to gastric neuroendocrine tumors."

Human case documenting the full AIG sequence of achlorhydria, antral G-cell hyperplasia, hypergastrinemia, and ECL hyperplasia-dysplasia-neoplasia.

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Histopathology

2

Oxyntic (Corpus-Restricted) Gland Atrophy

Corpus- and fundus-restricted atrophy of the oxyntic (acid-secreting) mucosa with loss of parietal and chief cells and a lymphoplasmacytic infiltrate; the antral mucosa is characteristically spared. This is the diagnostic pathological lesion of autoimmune gastritis (staged by the Sydney System / OLGA).

Show evidence (1 reference)

PMID:28102858 SUPPORT Human Clinical

"Atrophic body gastritis (AGB) is the pathological lesion of autoimmune gastritis, characterized by the disappearance of oxyntic mucosa"

Corpus-restricted disappearance of the oxyntic mucosa is the defining diagnostic pathological lesion of autoimmune gastritis.

Enterochromaffin-Like (ECL) Cell Hyperplasia

Hypergastrinemia-driven linear and nodular hyperplasia of corpus enterochromaffin-like (ECL) cells, which can progress through dysplasia to type 1 gastric neuroendocrine tumors.

Show evidence (1 reference)

PMID:34476276 SUPPORT Human Clinical

"The excess gastrin binds to enterochromaffin-like cells causing hyperplasia, which may progress to dysplasia and rarely to gastric neuroendocrine tumors."

Documents ECL cell hyperplasia progressing through dysplasia to neuroendocrine tumor in autoimmune gastritis.

⬡

Pathograph

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

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Phenotypes

9

Blood 2

Pernicious Anemia FREQUENT Megaloblastic anemia HP:0001889

Show evidence (2 references)

PMID:42367768 SUPPORT Human Clinical

"Autoimmune gastritis (AIG) is a chronic, organ-specific autoimmune disease characterized by the immune-mediated destruction of gastric parietal cells, leading to impaired acid secretion, vitamin B12 deficiency, and an increased risk of gastric malignancies."

Loss of intrinsic factor from parietal cell destruction causes vitamin B12 deficiency, the basis of pernicious (megaloblastic) anemia.

PMID:34829460 SUPPORT Human Clinical

"The clinical manifestation of the disease includes possible variants such as gastrointestinal, hematological (first of all, the formation of iron deficiency and B12-deficiency anemia), and neurological variants."

Lists B12-deficiency (megaloblastic/pernicious) anemia as a core hematological manifestation of chronic autoimmune gastritis.

Iron Deficiency Anemia FREQUENT Iron deficiency anemia HP:0001891

Show evidence (1 reference)

PMID:34829460 SUPPORT Human Clinical

"The clinical manifestation of the disease includes possible variants such as gastrointestinal, hematological (first of all, the formation of iron deficiency and B12-deficiency anemia), and neurological variants."

Identifies iron deficiency anemia as a leading hematological presentation of chronic autoimmune gastritis, often preceding B12 deficiency.

Nervous System 1

Peripheral Neuropathy OCCASIONAL Peripheral neuropathy HP:0009830

Other 6

Atrophic Gastritis OBLIGATE Atrophic gastritis HP:0002582

Achlorhydria VERY_FREQUENT Achlorhydria HP:0032448

Show evidence (1 reference)

PMID:42367768 SUPPORT Human Clinical

"Autoimmune gastritis (AIG) is a chronic, organ-specific autoimmune disease characterized by the immune-mediated destruction of gastric parietal cells, leading to impaired acid secretion, vitamin B12 deficiency, and an increased risk of gastric malignancies."

Parietal cell destruction abolishes gastric acid secretion, producing hypochlorhydria and achlorhydria.

Hypergastrinemia VERY_FREQUENT Hypergastrinemia HP:0500167

Glossitis OCCASIONAL Glossitis HP:0000206

Gastric Neuroendocrine Tumor OCCASIONAL Gastric carcinoid tumor HP:6000898

Show evidence (2 references)

PMID:31963924 SUPPORT Human Clinical

"persistent hypergastrinemia, generally accepted as causing g-NETs in CAG and ZES"

Persistent hypergastrinemia in chronic atrophic gastritis is the accepted cause of gastric neuroendocrine tumors (carcinoids).

PMID:42367768 SUPPORT Human Clinical

"we explore precision risk stratification models for gastric neuroendocrine tumors (gNETs) and gastric adenocarcinoma, emphasizing the roles of endoscopic surveillance and molecular biomarkers"

Confirms gastric neuroendocrine tumors and adenocarcinoma as the neoplastic risks of autoimmune gastritis that drive endoscopic surveillance.

Gastric Adenocarcinoma VERY_RARE Gastric adenocarcinoma HP:0033770

Show evidence (1 reference)

PMID:42367768 SUPPORT Human Clinical

"we explore precision risk stratification models for gastric neuroendocrine tumors (gNETs) and gastric adenocarcinoma, emphasizing the roles of endoscopic surveillance and molecular biomarkers"

Identifies gastric adenocarcinoma as a neoplastic risk of autoimmune gastritis requiring risk stratification and surveillance.

🧬

Genetic Associations

2

ATP4A (Risk factor)

Gene: ATP4A hgnc:819

Show evidence (1 reference)

PMID:28102858 SUPPORT Human Clinical

"This study aimed to assess autoantibodies against ATP4A and ATP4B subunits of parietal cells H+, K+-ATPase in atrophic body gastritis patients and controls."

Identifies the ATP4A subunit of the parietal cell H+/K+ ATPase as a target autoantigen in autoimmune (atrophic body) gastritis.

ATP4B (Risk factor)

Gene: ATP4B hgnc:820

Show evidence (1 reference)

PMID:28102858 SUPPORT Human Clinical

"This study aimed to assess autoantibodies against ATP4A and ATP4B subunits of parietal cells H+, K+-ATPase in atrophic body gastritis patients and controls."

Identifies the ATP4B subunit of the parietal cell H+/K+ ATPase as a target autoantigen in autoimmune (atrophic body) gastritis.

💊

Medical Actions

7

Vitamin B12 Replacement

Action: Pharmacotherapy NCIT:C15986

Agent: vitamin B12 CHEBI:176843

Parenteral (or high-dose oral) cobalamin replacement corrects and prevents the hematologic and neurologic consequences of B12 deficiency in pernicious anemia.

Iron Replacement

Action: Pharmacotherapy NCIT:C15986

Agent: iron(2+) CHEBI:29033

Oral or intravenous iron to correct the iron deficiency anemia that commonly precedes B12 deficiency in autoimmune gastritis.

Endoscopic Surveillance

Action: esophagogastroduodenoscopy MAXO:0001193

Periodic upper endoscopy with biopsy to monitor for gastric neuroendocrine tumors and gastric adenocarcinoma in patients with atrophic body gastritis.

Show evidence (1 reference)

PMID:42367768 SUPPORT Human Clinical

"we explore precision risk stratification models for gastric neuroendocrine tumors (gNETs) and gastric adenocarcinoma, emphasizing the roles of endoscopic surveillance and molecular biomarkers"

Supports endoscopic surveillance as the management strategy for the gastric neoplasia risk in autoimmune gastritis.

Netazepide (Gastrin/CCK2 Receptor Antagonist)

Action: Pharmacotherapy NCIT:C15986

Netazepide is an investigational oral gastrin/cholecystokinin-2 receptor (CCK2R) antagonist that blocks the trophic gastrin signal driving ECL cell proliferation, shrinking and eradicating type 1 gastric neuroendocrine tumors and normalizing chromogranin A in autoimmune atrophic gastritis.

Target Phenotypes: Gastric carcinoid tumor HP:6000898

Show evidence (1 reference)

PMID:27704617 SUPPORT Human Clinical

"Netazepide, a gastrin/cholecystokinin 2 receptor antagonist, once daily for 12 weeks reduced the number of tumours and size of the largest one in 16 patients with autoimmune chronic atrophic gastritis (CAG), achlorhydria, hypergastrinaemia and multiple gastric neuroendocrine tumours (type 1 gastric NETs)"

Human trial showing the gastrin/CCK2R antagonist netazepide reduces type 1 gastric NETs in autoimmune atrophic gastritis by blocking the trophic gastrin signal.

Endoscopic Resection of Gastric Neuroendocrine Tumors

Action: Endoscopic Mucosal Resection NCIT:C103242

Endoscopic resection is the first-line treatment for small, localized type 1 gastric neuroendocrine tumors; larger or higher-risk lesions are referred for surgical resection.

Target Phenotypes: Gastric carcinoid tumor HP:6000898

Show evidence (1 reference)

PMID:42228075 SUPPORT Human Clinical

"For type I gastric neuroendocrine neoplasms (gNEN) larger than 1 cm endoscopic resection should be performed, whereas for tumors larger than 2 cm surgical resection should be carried out."

States that endoscopic resection is the treatment for type 1 gastric neuroendocrine tumors, with surgery reserved for larger lesions.

Somatostatin Analog Therapy

Action: Pharmacotherapy NCIT:C15986

Agent: octreotide CHEBI:7726

Somatostatin analogs (e.g., octreotide, lanreotide) suppress gastrin release and are antiproliferative for type 1 gastric neuroendocrine tumors, reducing tumor size in patients with multiple or recurrent lesions.

Target Phenotypes: Gastric carcinoid tumor HP:6000898

Show evidence (1 reference)

PMID:40503415 SUPPORT Human Clinical

"Type I treatment usually involves endoscopic resection (ER), with surgical resection for recurrence. Somatostatin analogs (SSAs) can reduce tumor size, and the prognosis is generally excellent."

Supports somatostatin analogs as a size-reducing therapy for type 1 gastric neuroendocrine tumors.

Helicobacter pylori Eradication

Action: antimicrobial agent therapy MAXO:0001021

When Helicobacter pylori infection coexists with autoimmune gastritis, eradication therapy is recommended; in the subset where H. pylori contributes to the gastritis it can improve hematologic parameters and slow progression.

Show evidence (1 reference)

PMID:42254085 SUPPORT Human Clinical

"Rapid eradication of H. pylori can significantly improve hematologic parameters and prevent the progression of autoimmune gastritis."

Supports H. pylori eradication as a management step that can improve hematologic parameters and slow progression when the organism is present.

🌍

Environmental Factors

1

Helicobacter pylori Infection

H. pylori infection is proposed to trigger autoimmune gastritis through molecular mimicry between H. pylori antigens and the gastric H+/K+ ATPase, although autoimmune gastritis characteristically persists after the organism is no longer detectable.

Show evidence (1 reference)

PMID:21174235 SUPPORT Human Clinical

"a role for Helicobacter pylori as an infective trigger through molecular mimicry"

Supports H. pylori as a candidate infective trigger of autoimmune gastritis via molecular mimicry with the gastric H+/K+ ATPase.

🔬

Biochemical Markers

4

Anti-Parietal Cell Antibody (Increased)

Show evidence (1 reference)

PMID:28102858 SUPPORT Human Clinical

"Circulating autoantibodies targeting the H+/K+-ATPase proton pump of gastric parietal cells are considered markers of autoimmune gastritis"

Establishes anti-parietal cell (anti-H+/K+ ATPase) autoantibodies as the serological marker of autoimmune gastritis.

Anti-Intrinsic Factor Antibody (Increased)

Serum Gastrin (Increased)

Show evidence (1 reference)

PMID:40831016 SUPPORT Human Clinical

"a reduced PGI/PGII ratio combined with elevated G-17 levels provided excellent discrimination"

Elevated gastrin-17 accompanies corpus atrophic gastritis, reflecting the achlorhydria-driven hypergastrinemia of autoimmune gastritis.

Serum Pepsinogen I (Decreased)

Show evidence (1 reference)

PMID:40831016 SUPPORT Human Clinical

"a reduced PGI/PGII ratio combined with elevated G-17 levels provided excellent discrimination"

A reduced pepsinogen I/II ratio (with elevated gastrin-17) discriminates corpus atrophic gastritis, reflecting oxyntic gland loss.

{ }

Source YAML

click to show

name: Autoimmune Gastritis
creation_date: "2026-07-01T00:00:00Z"
category: Complex
disease_term:
  preferred_term: autoimmune gastritis
  term:
    id: MONDO:0031014
    label: autoimmune gastritis
description: >
  Autoimmune gastritis (AIG) is an organ-specific autoimmune disease characterized
  by chronic, corpus-restricted (oxyntic) atrophic gastritis driven by a
  CD4+ T cell-mediated immune response against the gastric parietal cell H+/K+
  ATPase (the gastric proton pump, encoded by ATP4A and ATP4B). Immune destruction
  of parietal cells causes loss of gastric acid secretion (hypochlorhydria and
  ultimately achlorhydria) and loss of intrinsic factor, producing vitamin B12
  malabsorption and pernicious anemia. Achlorhydria removes the negative feedback
  on antral G cells, causing hypergastrinemia, which drives enterochromaffin-like
  (ECL) cell hyperplasia and predisposes to type 1 gastric neuroendocrine tumors
  (carcinoids). Corpus atrophy with intestinal metaplasia also increases the risk
  of gastric adenocarcinoma. AIG frequently clusters with other autoimmune
  disorders, especially autoimmune thyroid disease (thyrogastric syndrome) and
  type 1 diabetes mellitus.
synonyms:
- Autoimmune atrophic gastritis
- Type A gastritis
- Autoimmune metaplastic atrophic gastritis
references:
- reference: PMID:42367768
  title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
- reference: PMID:34829460
  title: "Chronic Autoimmune Gastritis: Modern Diagnostic Principles."
- reference: PMID:31864909
  title: "Thyro-entero-gastric autoimmunity: Pathophysiology and implications for patient management."
- reference: PMID:35911678
  title: "Gastric Th17 Cells Specific for H+/K+-ATPase and Serum IL-17 Signature in Gastric Autoimmunity."
- reference: PMID:31963924
  title: "Proton Pump Inhibitor Use, Hypergastrinemia, and Gastric Carcinoids-What Is the Relationship?"
- reference: PMID:21174235
  title: "Cutting edge issues in autoimmune gastritis."
- reference: PMID:28102858
  title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
parents:
- Gastritis
- Autoimmune disease
classifications:
  harrisons_chapter:
  - classification_value: GASTROINTESTINAL
  - classification_value: IMMUNE_RHEUMATOLOGIC
pathophysiology:
- name: CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump
  description: >
    The central pathogenic event is a CD4+ T helper (Th1/Th17)-polarized
    autoimmune response directed against the alpha (ATP4A) and beta (ATP4B)
    subunits of the gastric H+/K+ ATPase expressed by parietal cells. Autoreactive
    T cells and parietal cell autoantibodies target the oxyntic mucosa of the
    gastric corpus and fundus, sparing the antrum. Molecular mimicry with
    Helicobacter pylori antigens has been proposed as an initiating trigger.
  cell_types:
  - preferred_term: CD4+ T helper cell
    term:
      id: CL:0000492
      label: CD4-positive helper T cell
    modifier: INCREASED
  - preferred_term: parietal cell
    term:
      id: CL:0000162
      label: parietal cell
    modifier: DECREASED
  biological_processes:
  - preferred_term: adaptive immune response against the H+/K+ ATPase
    term:
      id: GO:0002250
      label: adaptive immune response
    modifier: INCREASED
  - preferred_term: parietal cell apoptosis
    term:
      id: GO:0006915
      label: apoptotic process
    modifier: INCREASED
  downstream:
  - target: Parietal Cell Destruction and Oxyntic Atrophy
    description: Autoreactive CD4+ T cells and autoantibodies drive parietal cell apoptosis and loss.
    hypothesis_groups:
    - canonical_th1_effector_polarization
    - emerging_th17_effector_polarization
  evidence:
  - reference: PMID:35911678
    reference_title: "Gastric Th17 Cells Specific for H+/K+-ATPase and Serum IL-17 Signature in Gastric Autoimmunity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The gastric parietal cell proton pump H+/K+-adenosine triphosphatase (H+/K+-ATPase) is the major autoantigen in AIG."
    explanation: Identifies the gastric H+/K+ ATPase as the principal autoantigen targeted in autoimmune gastritis.
  - reference: PMID:35911678
    reference_title: "Gastric Th17 Cells Specific for H+/K+-ATPase and Serum IL-17 Signature in Gastric Autoimmunity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gastric LPMCs from all AIG patients, but not those from HCs, were activated by H+/K+-ATPase and were able to proliferate and produce high levels of IL-17A and IL-17F."
    explanation: Demonstrates antigen-specific gastric T cell activation and proliferation in response to the H+/K+ ATPase autoantigen in AIG patients.
  - reference: PMID:42367768
    reference_title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autoimmune gastritis (AIG) is a chronic, organ-specific autoimmune disease characterized by the immune-mediated destruction of gastric parietal cells, leading to impaired acid secretion, vitamin B12 deficiency, and an increased risk of gastric malignancies."
    explanation: Establishes immune-mediated parietal cell destruction as the central pathogenic mechanism of autoimmune gastritis.
  - reference: PMID:21174235
    reference_title: "Cutting edge issues in autoimmune gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autoimmune gastritis is the outcome of a pathological CD4 T cell-mediated autoimmune response directed against the gastric H/K-ATPase."
    explanation: Confirms that the autoimmune response driving AIG is CD4 T cell-mediated and directed against the gastric H+/K+ ATPase.
- name: Parietal Cell Destruction and Oxyntic Atrophy
  description: >
    Immune-mediated destruction of parietal cells leads to progressive atrophy of
    the oxyntic (acid-secreting) mucosa restricted to the corpus and fundus. Loss
    of parietal cells abolishes both gastric acid and intrinsic factor secretion,
    and the mucosa undergoes pseudopyloric and intestinal metaplasia.
  cell_types:
  - preferred_term: parietal cell
    term:
      id: CL:0000162
      label: parietal cell
    modifier: ABSENT
  biological_processes:
  - preferred_term: gastric acid secretion
    term:
      id: GO:0001696
      label: gastric acid secretion
    modifier: DECREASED
  downstream:
  - target: Atrophic Gastritis
    description: Progressive parietal cell loss produces corpus-restricted atrophic gastritis.
  - target: Achlorhydria
    description: Parietal cell loss abolishes gastric acid secretion.
  - target: Iron Deficiency Anemia
    description: Loss of gastric acid impairs acid-dependent dietary iron absorption, causing iron deficiency anemia.
  - target: Intrinsic Factor Deficiency and B12 Malabsorption
    description: Parietal cell loss abolishes intrinsic factor secretion.
  - target: Hypergastrinemia and ECL Cell Hyperplasia
    description: Loss of luminal acid removes negative feedback on antral gastrin release.
  - target: Gastric Adenocarcinoma
    description: >-
      Oxyntic atrophy with intestinal metaplasia forms a precancerous field
      predisposing to intestinal-type gastric adenocarcinoma.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
  evidence:
  - reference: PMID:28102858
    reference_title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atrophic body gastritis (AGB) is the pathological lesion of autoimmune gastritis, characterized by the disappearance of oxyntic mucosa"
    explanation: Confirms that parietal-cell destruction produces corpus-restricted disappearance of the oxyntic mucosa (atrophic body gastritis).
- name: Intrinsic Factor Deficiency and B12 Malabsorption
  description: >
    Loss of intrinsic factor (encoded by CBLIF/GIF) secreted by parietal cells,
    compounded by anti-intrinsic factor autoantibodies, prevents ileal absorption
    of dietary vitamin B12 (cobalamin), causing systemic cobalamin deficiency and
    pernicious anemia.
  cell_types:
  - preferred_term: parietal cell
    term:
      id: CL:0000162
      label: parietal cell
    modifier: ABSENT
  downstream:
  - target: Pernicious Anemia
    description: Cobalamin deficiency impairs erythropoiesis, causing megaloblastic anemia.
  - target: Peripheral Neuropathy
    description: Cobalamin deficiency causes neurological injury including subacute combined degeneration.
  - target: Glossitis
    description: Cobalamin deficiency causes atrophic glossitis.
  evidence:
  - reference: PMID:31080562
    reference_title: "Intrinsic factor recognition promotes T helper 17/T helper 1 autoimmune gastric inflammation in patients with pernicious anemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The intrinsic factor is the major humoral autoantigen in pernicious anemia/autoimmune gastritis."
    explanation: Establishes intrinsic factor as the major humoral autoantigen whose loss (and autoantibody targeting) causes the B12 malabsorption of pernicious anemia.
  - reference: PMID:21174235
    reference_title: "Cutting edge issues in autoimmune gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "megaloblastic pernicious anemia arising from vitamin B12 deficiency"
    explanation: Links the intrinsic-factor-dependent vitamin B12 deficiency to megaloblastic pernicious anemia.
- name: Hypergastrinemia and ECL Cell Hyperplasia
  description: >
    Achlorhydria removes the acid-mediated negative feedback on antral G cells,
    producing marked hypergastrinemia. Chronically elevated gastrin is trophic for
    enterochromaffin-like (ECL) cells in the corpus, driving ECL cell hyperplasia
    that can progress through dysplasia to type 1 gastric neuroendocrine tumors.
  cell_types:
  - preferred_term: antral G cell
    term:
      id: CL:0000508
      label: type G enteroendocrine cell
    modifier: INCREASED
  - preferred_term: enterochromaffin-like cell
    term:
      id: CL:0000504
      label: enterochromaffin-like cell
    modifier: INCREASED
  downstream:
  - target: Hypergastrinemia
    description: Achlorhydria-driven loss of feedback on antral G cells produces marked hypergastrinemia.
  - target: Gastric Neuroendocrine Tumor
    description: Sustained gastrin drive promotes ECL hyperplasia to neoplasia.
  evidence:
  - reference: PMID:31963924
    reference_title: "Proton Pump Inhibitor Use, Hypergastrinemia, and Gastric Carcinoids-What Is the Relationship?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "tumorigenesis is mediated by gastrin's effects on the CCK2R-receptor on ECL-cells that in turn leads to hyperplasia, dysplasia, and finally neoplasia"
    explanation: Describes the gastrin-CCK2R trophic pathway by which chronic hypergastrinemia drives ECL cell hyperplasia, dysplasia, and neoplasia.
  - reference: PMID:34476276
    reference_title: "Progression From Antral G-Cell Hyperplasia to Gastric Neuroendocrine Tumor in a Patient With Autoimmune Gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This leads to the absence of gastric acid production, which causes compensatory hyperplasia of gastric antral G-cells leading to hypergastrinemia. The excess gastrin binds to enterochromaffin-like cells causing hyperplasia, which may progress to dysplasia and rarely to gastric neuroendocrine tumors."
    explanation: Human case documenting the full AIG sequence of achlorhydria, antral G-cell hyperplasia, hypergastrinemia, and ECL hyperplasia-dysplasia-neoplasia.
phenotypes:
- category: Digestive
  name: Atrophic Gastritis
  description: >
    Chronic atrophic gastritis restricted to the gastric corpus and fundus
    (oxyntic mucosa), with loss of parietal and chief cells and replacement by
    metaplastic epithelium.
  frequency: OBLIGATE
  phenotype_term:
    preferred_term: Atrophic gastritis
    term:
      id: HP:0002582
      label: Atrophic gastritis
- category: Digestive
  name: Achlorhydria
  description: >
    Loss of gastric acid secretion resulting from destruction of acid-secreting
    parietal cells.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Achlorhydria
    term:
      id: HP:0032448
      label: Achlorhydria
  evidence:
  - reference: PMID:42367768
    reference_title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autoimmune gastritis (AIG) is a chronic, organ-specific autoimmune disease characterized by the immune-mediated destruction of gastric parietal cells, leading to impaired acid secretion, vitamin B12 deficiency, and an increased risk of gastric malignancies."
    explanation: Parietal cell destruction abolishes gastric acid secretion, producing hypochlorhydria and achlorhydria.
- category: Hematologic
  name: Pernicious Anemia
  description: >
    Megaloblastic anemia from vitamin B12 deficiency caused by intrinsic factor
    loss; the classic hematologic complication of autoimmune gastritis.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Megaloblastic anemia
    term:
      id: HP:0001889
      label: Megaloblastic anemia
  evidence:
  - reference: PMID:42367768
    reference_title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Autoimmune gastritis (AIG) is a chronic, organ-specific autoimmune disease characterized by the immune-mediated destruction of gastric parietal cells, leading to impaired acid secretion, vitamin B12 deficiency, and an increased risk of gastric malignancies."
    explanation: Loss of intrinsic factor from parietal cell destruction causes vitamin B12 deficiency, the basis of pernicious (megaloblastic) anemia.
  - reference: PMID:34829460
    reference_title: "Chronic Autoimmune Gastritis: Modern Diagnostic Principles."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical manifestation of the disease includes possible variants such as gastrointestinal, hematological (first of all, the formation of iron deficiency and B12-deficiency anemia), and neurological variants."
    explanation: Lists B12-deficiency (megaloblastic/pernicious) anemia as a core hematological manifestation of chronic autoimmune gastritis.
- category: Hematologic
  name: Iron Deficiency Anemia
  description: >
    Iron deficiency anemia due to impaired acid-dependent iron absorption; often
    the earliest hematologic manifestation, preceding B12 deficiency.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Iron deficiency anemia
    term:
      id: HP:0001891
      label: Iron deficiency anemia
  evidence:
  - reference: PMID:34829460
    reference_title: "Chronic Autoimmune Gastritis: Modern Diagnostic Principles."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The clinical manifestation of the disease includes possible variants such as gastrointestinal, hematological (first of all, the formation of iron deficiency and B12-deficiency anemia), and neurological variants."
    explanation: Identifies iron deficiency anemia as a leading hematological presentation of chronic autoimmune gastritis, often preceding B12 deficiency.
- category: Laboratory
  name: Hypergastrinemia
  description: >
    Markedly elevated serum gastrin resulting from achlorhydria-driven loss of
    feedback inhibition on antral G cells.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Hypergastrinemia
    term:
      id: HP:0500167
      label: Hypergastrinemia
- category: Neurologic
  name: Peripheral Neuropathy
  description: >
    Vitamin B12 deficiency causes peripheral neuropathy and, when severe, subacute
    combined degeneration of the spinal cord with paresthesias and sensory ataxia.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Peripheral neuropathy
    term:
      id: HP:0009830
      label: Peripheral neuropathy
- category: Digestive
  name: Glossitis
  description: >
    Atrophic glossitis (a smooth, sore, red tongue) associated with vitamin B12
    deficiency.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Glossitis
    term:
      id: HP:0000206
      label: Glossitis
- category: Neoplasm
  name: Gastric Neuroendocrine Tumor
  description: >
    Type 1 gastric neuroendocrine tumors (carcinoids) arising from hypergastrinemia-driven
    ECL cell hyperplasia; usually indolent and multifocal.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Gastric carcinoid tumor
    term:
      id: HP:6000898
      label: Gastric carcinoid tumor
  evidence:
  - reference: PMID:31963924
    reference_title: "Proton Pump Inhibitor Use, Hypergastrinemia, and Gastric Carcinoids-What Is the Relationship?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "persistent hypergastrinemia, generally accepted as causing g-NETs in CAG and ZES"
    explanation: Persistent hypergastrinemia in chronic atrophic gastritis is the accepted cause of gastric neuroendocrine tumors (carcinoids).
  - reference: PMID:42367768
    reference_title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we explore precision risk stratification models for gastric neuroendocrine tumors (gNETs) and gastric adenocarcinoma, emphasizing the roles of endoscopic surveillance and molecular biomarkers"
    explanation: Confirms gastric neuroendocrine tumors and adenocarcinoma as the neoplastic risks of autoimmune gastritis that drive endoscopic surveillance.
- category: Neoplasm
  name: Gastric Adenocarcinoma
  description: >
    Corpus-restricted atrophy with intestinal metaplasia is a precancerous field
    that confers an increased risk of gastric (intestinal-type) adenocarcinoma,
    the basis for endoscopic surveillance in autoimmune gastritis.
  frequency: VERY_RARE
  phenotype_term:
    preferred_term: Gastric adenocarcinoma
    term:
      id: HP:0033770
      label: Gastric adenocarcinoma
  evidence:
  - reference: PMID:42367768
    reference_title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we explore precision risk stratification models for gastric neuroendocrine tumors (gNETs) and gastric adenocarcinoma, emphasizing the roles of endoscopic surveillance and molecular biomarkers"
    explanation: Identifies gastric adenocarcinoma as a neoplastic risk of autoimmune gastritis requiring risk stratification and surveillance.
biochemical:
- name: Anti-Parietal Cell Antibody
  notes: >
    Autoantibodies against the gastric H+/K+ ATPase (parietal cell canalicular
    antigen); the serological hallmark of autoimmune gastritis, present in the
    majority of patients.
  presence: Increased
  evidence:
  - reference: PMID:28102858
    reference_title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Circulating autoantibodies targeting the H+/K+-ATPase proton pump of gastric parietal cells are considered markers of autoimmune gastritis"
    explanation: Establishes anti-parietal cell (anti-H+/K+ ATPase) autoantibodies as the serological marker of autoimmune gastritis.
- name: Anti-Intrinsic Factor Antibody
  notes: >
    Autoantibodies against intrinsic factor; less sensitive but highly specific
    for autoimmune gastritis and pernicious anemia.
  presence: Increased
- name: Serum Gastrin
  notes: >
    Fasting serum gastrin is markedly elevated in autoimmune gastritis due to
    achlorhydria.
  presence: Increased
  evidence:
  - reference: PMID:40831016
    reference_title: "Evaluation of Pepsinogen I, II, Gastrin 17 and Helicobacter pylori IgG in Atrophic Gastritis: A Head-To-Head Comparison of Lateral Flow and Enzyme-Linked Immunosorbent Assays."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a reduced PGI/PGII ratio combined with elevated G-17 levels provided excellent discrimination"
    explanation: Elevated gastrin-17 accompanies corpus atrophic gastritis, reflecting the achlorhydria-driven hypergastrinemia of autoimmune gastritis.
- name: Serum Pepsinogen I
  notes: >
    Low serum pepsinogen I and a low pepsinogen I/II ratio reflect loss of chief
    and parietal cells in the atrophic oxyntic mucosa.
  presence: Decreased
  evidence:
  - reference: PMID:40831016
    reference_title: "Evaluation of Pepsinogen I, II, Gastrin 17 and Helicobacter pylori IgG in Atrophic Gastritis: A Head-To-Head Comparison of Lateral Flow and Enzyme-Linked Immunosorbent Assays."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a reduced PGI/PGII ratio combined with elevated G-17 levels provided excellent discrimination"
    explanation: A reduced pepsinogen I/II ratio (with elevated gastrin-17) discriminates corpus atrophic gastritis, reflecting oxyntic gland loss.
genetic:
- name: ATP4A
  notes: >
    Alpha subunit of the gastric H+/K+ ATPase; the major autoantigen targeted by
    parietal cell autoantibodies and autoreactive T cells in autoimmune gastritis.
  gene_term:
    preferred_term: ATP4A
    term:
      id: hgnc:819
      label: ATP4A
  association: Risk factor
  evidence:
  - reference: PMID:28102858
    reference_title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study aimed to assess autoantibodies against ATP4A and ATP4B subunits of parietal cells H+, K+-ATPase in atrophic body gastritis patients and controls."
    explanation: Identifies the ATP4A subunit of the parietal cell H+/K+ ATPase as a target autoantigen in autoimmune (atrophic body) gastritis.
- name: ATP4B
  notes: >
    Beta subunit of the gastric H+/K+ ATPase; a co-target autoantigen in
    autoimmune gastritis.
  gene_term:
    preferred_term: ATP4B
    term:
      id: hgnc:820
      label: ATP4B
  association: Risk factor
  evidence:
  - reference: PMID:28102858
    reference_title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "This study aimed to assess autoantibodies against ATP4A and ATP4B subunits of parietal cells H+, K+-ATPase in atrophic body gastritis patients and controls."
    explanation: Identifies the ATP4B subunit of the parietal cell H+/K+ ATPase as a target autoantigen in autoimmune (atrophic body) gastritis.
environmental:
- name: Helicobacter pylori Infection
  description: >
    H. pylori infection is proposed to trigger autoimmune gastritis through
    molecular mimicry between H. pylori antigens and the gastric H+/K+ ATPase,
    although autoimmune gastritis characteristically persists after the organism
    is no longer detectable.
  evidence:
  - reference: PMID:21174235
    reference_title: "Cutting edge issues in autoimmune gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a role for Helicobacter pylori as an infective trigger through molecular mimicry"
    explanation: Supports H. pylori as a candidate infective trigger of autoimmune gastritis via molecular mimicry with the gastric H+/K+ ATPase.
inheritance:
- name: Polygenic inheritance
  description: >
    Complex, non-Mendelian autoimmune disease with polygenic susceptibility -
    HLA-DQB1 plus non-HLA loci (PTPN22, IL2RA) shared with other organ-specific
    autoimmune diseases - acting together with environmental factors.
  inheritance_term:
    preferred_term: Polygenic inheritance
    term:
      id: HP:0010982
      label: Polygenic inheritance
  evidence:
  - reference: PMID:34145262
    reference_title: "Genome-wide association study identifies five risk loci for pernicious anemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "We conduct a genome-wide association study meta-analysis in 2166 cases and 659,516 European controls from population-based biobanks and identify genome-wide significant signals in or near the PTPN22"
    explanation: A GWAS identifies multiple risk loci (PTPN22, HLA-DQB1, IL2RA) for pernicious anemia / autoimmune gastritis, establishing polygenic inheritance.
prevalence:
- population: General population
  percentage: 2.0
  evidence:
  - reference: PMID:28102858
    reference_title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "prevalence of ~2% in the general population and up to 10% in patients with other autoimmune diseases, such as type I diabetes or autoimmune thyroid disease."
    explanation: Establishes ~2% general-population prevalence, rising to ~10% among patients with other autoimmune diseases (thyrogastric clustering).
histopathology:
- name: Oxyntic (Corpus-Restricted) Gland Atrophy
  description: >
    Corpus- and fundus-restricted atrophy of the oxyntic (acid-secreting) mucosa
    with loss of parietal and chief cells and a lymphoplasmacytic infiltrate; the
    antral mucosa is characteristically spared. This is the diagnostic pathological
    lesion of autoimmune gastritis (staged by the Sydney System / OLGA).
  diagnostic: true
  evidence:
  - reference: PMID:28102858
    reference_title: "Luminescent Immunoprecipitation System (LIPS) for Detection of Autoantibodies Against ATP4A and ATP4B Subunits of Gastric Proton Pump H+,K+-ATPase in Atrophic Body Gastritis Patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Atrophic body gastritis (AGB) is the pathological lesion of autoimmune gastritis, characterized by the disappearance of oxyntic mucosa"
    explanation: Corpus-restricted disappearance of the oxyntic mucosa is the defining diagnostic pathological lesion of autoimmune gastritis.
- name: Enterochromaffin-Like (ECL) Cell Hyperplasia
  description: >
    Hypergastrinemia-driven linear and nodular hyperplasia of corpus
    enterochromaffin-like (ECL) cells, which can progress through dysplasia to
    type 1 gastric neuroendocrine tumors.
  evidence:
  - reference: PMID:34476276
    reference_title: "Progression From Antral G-Cell Hyperplasia to Gastric Neuroendocrine Tumor in a Patient With Autoimmune Gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The excess gastrin binds to enterochromaffin-like cells causing hyperplasia, which may progress to dysplasia and rarely to gastric neuroendocrine tumors."
    explanation: Documents ECL cell hyperplasia progressing through dysplasia to neuroendocrine tumor in autoimmune gastritis.
treatments:
- name: Vitamin B12 Replacement
  description: >
    Parenteral (or high-dose oral) cobalamin replacement corrects and prevents the
    hematologic and neurologic consequences of B12 deficiency in pernicious anemia.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: vitamin B12
      term:
        id: CHEBI:176843
        label: vitamin B12
- name: Iron Replacement
  description: >
    Oral or intravenous iron to correct the iron deficiency anemia that commonly
    precedes B12 deficiency in autoimmune gastritis.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: iron(2+)
      term:
        id: CHEBI:29033
        label: iron(2+)
- name: Endoscopic Surveillance
  description: >
    Periodic upper endoscopy with biopsy to monitor for gastric neuroendocrine
    tumors and gastric adenocarcinoma in patients with atrophic body gastritis.
  treatment_term:
    preferred_term: esophagogastroduodenoscopy
    term:
      id: MAXO:0001193
      label: esophagogastroduodenoscopy
  evidence:
  - reference: PMID:42367768
    reference_title: "Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "we explore precision risk stratification models for gastric neuroendocrine tumors (gNETs) and gastric adenocarcinoma, emphasizing the roles of endoscopic surveillance and molecular biomarkers"
    explanation: Supports endoscopic surveillance as the management strategy for the gastric neoplasia risk in autoimmune gastritis.
- name: Netazepide (Gastrin/CCK2 Receptor Antagonist)
  description: >
    Netazepide is an investigational oral gastrin/cholecystokinin-2 receptor
    (CCK2R) antagonist that blocks the trophic gastrin signal driving ECL cell
    proliferation, shrinking and eradicating type 1 gastric neuroendocrine tumors
    and normalizing chromogranin A in autoimmune atrophic gastritis.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  target_phenotypes:
  - preferred_term: Gastric carcinoid tumor
    term:
      id: HP:6000898
      label: Gastric carcinoid tumor
  evidence:
  - reference: PMID:27704617
    reference_title: "Netazepide, a gastrin/cholecystokinin-2 receptor antagonist, can eradicate gastric neuroendocrine tumours in patients with autoimmune chronic atrophic gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Netazepide, a gastrin/cholecystokinin 2 receptor antagonist, once daily for 12 weeks reduced the number of tumours and size of the largest one in 16 patients with autoimmune chronic atrophic gastritis (CAG), achlorhydria, hypergastrinaemia and multiple gastric neuroendocrine tumours (type 1 gastric NETs)"
    explanation: Human trial showing the gastrin/CCK2R antagonist netazepide reduces type 1 gastric NETs in autoimmune atrophic gastritis by blocking the trophic gastrin signal.
- name: Endoscopic Resection of Gastric Neuroendocrine Tumors
  description: >
    Endoscopic resection is the first-line treatment for small, localized type 1
    gastric neuroendocrine tumors; larger or higher-risk lesions are referred for
    surgical resection.
  treatment_term:
    preferred_term: Endoscopic Mucosal Resection
    term:
      id: NCIT:C103242
      label: Endoscopic Mucosal Resection
  target_phenotypes:
  - preferred_term: Gastric carcinoid tumor
    term:
      id: HP:6000898
      label: Gastric carcinoid tumor
  evidence:
  - reference: PMID:42228075
    reference_title: "[Gastric neuroendocrine neoplasms: update on endoscopic and surgical management]."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "For type I gastric neuroendocrine neoplasms (gNEN) larger than 1 cm endoscopic resection should be performed, whereas for tumors larger than 2 cm surgical resection should be carried out."
    explanation: States that endoscopic resection is the treatment for type 1 gastric neuroendocrine tumors, with surgery reserved for larger lesions.
- name: Somatostatin Analog Therapy
  description: >
    Somatostatin analogs (e.g., octreotide, lanreotide) suppress gastrin release
    and are antiproliferative for type 1 gastric neuroendocrine tumors, reducing
    tumor size in patients with multiple or recurrent lesions.
  therapeutic_modality: PEPTIDE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: octreotide
      term:
        id: CHEBI:7726
        label: octreotide
  target_phenotypes:
  - preferred_term: Gastric carcinoid tumor
    term:
      id: HP:6000898
      label: Gastric carcinoid tumor
  evidence:
  - reference: PMID:40503415
    reference_title: "Last decade of advances in gastric neuroendocrine tumors: Innovations, challenges, and future directions."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Type I treatment usually involves endoscopic resection (ER), with surgical resection for recurrence. Somatostatin analogs (SSAs) can reduce tumor size, and the prognosis is generally excellent."
    explanation: Supports somatostatin analogs as a size-reducing therapy for type 1 gastric neuroendocrine tumors.
- name: Helicobacter pylori Eradication
  description: >
    When Helicobacter pylori infection coexists with autoimmune gastritis,
    eradication therapy is recommended; in the subset where H. pylori contributes
    to the gastritis it can improve hematologic parameters and slow progression.
  treatment_term:
    preferred_term: antimicrobial agent therapy
    term:
      id: MAXO:0001021
      label: antimicrobial agent therapy
  evidence:
  - reference: PMID:42254085
    reference_title: "Pernicious Anemia and Helicobacter pylori Infection: What a Hematologist Needs to Know?"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Rapid eradication of H. pylori can significantly improve hematologic parameters and prevent the progression of autoimmune gastritis."
    explanation: Supports H. pylori eradication as a management step that can improve hematologic parameters and slow progression when the organism is present.
mechanistic_hypotheses:
- hypothesis_group_id: canonical_primary_autoimmune_hk_atpase_origin
  hypothesis_label: Canonical Primary Autoimmunity Against the Gastric H+/K+ ATPase
  status: CANONICAL
  description: >-
    Autoimmune gastritis is a primary organ-specific autoimmune disease driven by
    a breakdown of self-tolerance to the parietal-cell H+/K+ ATPase (ATP4A/ATP4B),
    with CD4 T-cell-mediated parietal cell destruction that is self-sustaining. The
    tolerance defect implicates the beta subunit: although H/K-ATPase alpha-subunit
    (ATP4A) mRNA is expressed in the thymus, thymic expression alone does not
    tolerize the pathogenic T-cell repertoire, and it is the beta subunit (ATP4B),
    absent from the thymus, that behaves as the dominant autoantigen. The murine
    disease induced by neonatal thymectomy is T-cell-mediated, and monogenic
    tolerance defects (AIRE/APECED, FOXP3/IPEX) produce autoimmune gastritis as part
    of polyautoimmunity. Two independent hypothesis-search runs (see notes) concur
    that this primary/central-tolerance account is best treated as one of several
    parallel initiating pathways feeding a shared effector cascade, rather than as
    an infection-independent sole origin.
  evidence:
  - reference: PMID:9272282
    reference_title: "Expression of the gastric H/K-ATPase alpha-subunit in the thymus may explain the dominant role of the beta-subunit in the pathogenesis of autoimmune gastritis."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "The murine disease induced by neonatal thymectomy is T cell-mediated."
    explanation: The T-cell-mediated neonatal-thymectomy model supports a T-cell-driven autoimmune origin of gastritis.
  - reference: PMID:16237067
    reference_title: "Promiscuous thymic expression of an autoantigen gene does not result in negative selection of pathogenic T cells."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "thymic mRNA expression alone cannot predict a contribution to thymic tolerance."
    explanation: Corrects the tolerance framing - thymic H/K-ATPase alpha-subunit mRNA expression does not negatively select pathogenic T cells, so central tolerance to the alpha subunit is not protective; the beta subunit (absent from the thymus) is the dominant autoantigen.
  notes: >-
    Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED:
    a claude_code report
    (kb/hypotheses/Autoimmune_Gastritis/canonical_primary_autoimmune_hk_atpase_origin/claude_code.md)
    and a deeper openscientist report (same directory, openscientist.md; 127
    papers, 17 findings over 5 iterations). Both retain the CD4 T-cell / H+/K+
    ATPase effector mechanism as CANONICAL but judge the etiological claim of a
    purely primary, infection-independent origin overstated: the disease is best
    modeled as multiple parallel initiating pathways - primary central-tolerance
    defect, H. pylori molecular mimicry (T-cell level; see
    alternative_hpylori_molecular_mimicry_origin), neonatal roseolovirus thymic
    disruption, and peripheral checkpoint failure (anti-PD-1/anti-CTLA-4 gastritis)
    - all converging on the same self-sustaining effector cascade. The ATP4A/ATP4B
    tolerance correction flagged by both runs (alpha thymic expression does not
    tolerize; ATP4B is the thymus-absent dominant autoantigen) has been folded into
    the description above (PMID:16237067). Follow-up recommended by openscientist:
    split into separate CANONICAL effector and qualified etiological-trigger
    hypotheses, and add an upstream "incomplete central tolerance to ATP4B" node.
- hypothesis_group_id: alternative_hpylori_molecular_mimicry_origin
  hypothesis_label: Alternative H. pylori Molecular-Mimicry ("Hit-and-Run") Origin
  status: ALTERNATIVE
  description: >-
    Autoimmune gastritis is initiated by Helicobacter pylori infection via
    molecular mimicry between H. pylori antigens and the gastric H+/K+ ATPase,
    generating cross-reactive T- and B-cell responses that, through epitope
    spreading and bystander activation in a genetically susceptible host, become
    self-perpetuating autoimmunity and persist after the organism is cleared
    (established AIG is frequently H. pylori-negative). A corollary is that a
    subset of cases are reversible with early eradication. Causation in humans
    remains unproven and is the basis of a knowledge-gap discussion.
  evidence:
  - reference: PMID:21174235
    reference_title: "Cutting edge issues in autoimmune gastritis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "a role for Helicobacter pylori as an infective trigger through molecular mimicry"
    explanation: States H. pylori as a candidate infective trigger of autoimmune gastritis via molecular mimicry.
  - reference: PMID:42254085
    reference_title: "Pernicious Anemia and Helicobacter pylori Infection: What a Hematologist Needs to Know?"
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Rapid eradication of H. pylori can significantly improve hematologic parameters and prevent the progression of autoimmune gastritis."
    explanation: A reversible, H. pylori-attributable presentation is consistent with an infection-triggered origin in a subset of cases.
  - reference: PMID:38976374
    reference_title: "Distinguishing Features of Autoimmune Gastritis Depending on Previous Helicobacter pylori Infection or Positivity to Anti-Parietal Cell Antibodies: Results From the Autoimmune gastRItis Study grOup (ARIOSO)."
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "H. pylori -naive patients were more likely to have a first-degree family history of AIG (14.7% vs 8.9%; P = 0.012), type 1 diabetes mellitus (4.9% vs 2.3%; P = 0.025), and pernicious anemia (30.9% vs 21.1%; P = 0.003)."
    explanation: The largest AIG cohort (n=1,598) identifies H. pylori-naive AIG as a distinct entity with stronger familial/autoimmune signatures, limiting the mimicry hypothesis to a subset rather than a general etiology.
  notes: >-
    Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED /
    UNRESOLVED: a claude_code report
    (kb/hypotheses/Autoimmune_Gastritis/alternative_hpylori_molecular_mimicry_origin/claude_code.md)
    and a deeper openscientist report (same directory, openscientist.md). H. pylori-
    to-H+/K+ ATPase cross-reactivity is documented at the T-cell level (cross-reactive
    gastric CD4 Th1 clones; urease beta-subunit homology; LPS Lewis-antigen mimicry),
    and early-stage non-atrophic AIG is reported to heal after eradication in ~80% of
    cases (supporting a time-limited "hit-and-run" window). However the model is
    causally unproven and non-general: molecular mimicry is refuted at the
    autoantibody level (antigastric autoantibodies do not absorb to H. pylori;
    Faller), a large fraction of AIG patients (~29-79%) are H. pylori-naive and form a
    distinct familial/autoimmune-enriched entity (ARIOSO n=1,598; PMID:38976374),
    Treg-depletion mouse models produce AIG with no infection, and some H. pylori-AIG
    associations may be inflated by diagnostic misclassification (urease-positive
    non-H. pylori bacteria overgrowing the achlorhydric stomach). Retained ALTERNATIVE,
    best read as a subset-initiation mechanism.
- hypothesis_group_id: canonical_th1_effector_polarization
  hypothesis_label: Canonical Th1/IFN-gamma Effector Polarization
  status: CANONICAL
  description: >-
    The effector arm driving parietal-cell destruction has classically been
    modeled as Th1/IFN-gamma-polarized, based on murine neonatal-thymectomy and
    TCR-transgenic effector-transfer systems specific for the H+/K+ ATPase.
  evidence:
  - reference: PMID:18641328
    reference_title: "Th1, Th2, and Th17 effector T cell-induced autoimmune gastritis differs in pathological pattern and in susceptibility to suppression by regulatory T cells."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We have evaluated the capacity of fully differentiated Th1, Th2, and Th17 cells derived from a mouse bearing a transgenic TCR specific for the gastric parietal cell antigen, H(+)K(+)-ATPase, to induce autoimmune gastritis after transfer to immunodeficient recipients."
    explanation: Effector-transfer model in which Th1 (among other subsets) specific for the H+/K+ ATPase induces autoimmune gastritis.
  - reference: PMID:15763992
    reference_title: "Molecular specificity and functional properties of autoreactive T-cell response in human gastric autoimmunity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The majority of the autoreactive T cell clones secreted IFN-gamma and showed a T helper 1 (Th1) profile."
    explanation: Human gastric H+/K+ ATPase-reactive CD4 clones are predominantly Th1 (IFN-gamma) and cytotoxic, directly supporting the Th1 effector arm in human disease.
  - reference: PMID:22777705
    reference_title: "Both IFN-gamma and IL-17 are required for the development of severe autoimmune gastritis."
    supports: PARTIAL
    evidence_source: MODEL_ORGANISM
    snippet: "both are required for the disease to progress to the late pathogenic stage that includes significant tissue disruption."
    explanation: IFN-gamma and IL-17 are co-required for severe disease (and CD8 T cells are the dominant IFN-gamma source), qualifying a Th1-exclusive model.
  notes: >-
    Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED: a
    claude_code report
    (kb/hypotheses/Autoimmune_Gastritis/canonical_th1_effector_polarization/claude_code.md)
    and an openscientist report (same directory, openscientist.md). Both retain
    Th1/IFN-gamma as foundational and real (anti-IFN-gamma blockade prevents murine
    disease; human gastric H+/K+ ATPase-reactive CD4 clones are predominantly Th1
    and cytotoxic via perforin/Fas-FasL; IFN-gamma directly kills gastric
    epithelium in organoids; the PTPN22 pernicious-anemia risk variant favors Th1
    over Th17), but neither supports a Th1-exclusive model - it is one arm of a
    cooperative multi-cytokine / multi-cell-type program: CD8 T cells are the
    dominant IFN-gamma source, IFN-gamma plus IL-17 are co-required for severe
    disease (PMID:22777705), IL-13 independently drives the post-atrophy
    metaplastic transformation, and the human intrinsic-factor-reactive /
    pernicious-anemia compartment is Th17-dominant (see
    emerging_th17_effector_polarization). Caveat: Th1 dominance is demonstrated
    most robustly in TCR-transgenic / monoclonal systems, which may overrepresent
    it relative to polyclonal disease.
- hypothesis_group_id: emerging_th17_effector_polarization
  hypothesis_label: Emerging Th17/IL-17 Effector Contribution
  status: EMERGING
  description: >-
    Human data show a gastric H+/K+ ATPase-specific Th17/IL-17 signature, and
    effector-transfer models show that Th1, Th2, and Th17 cells can each induce
    autoimmune gastritis with distinct pathology and differing susceptibility to
    regulatory T-cell suppression. Which effector arm dominates human disease, and
    whether it shifts over the disease course, is unresolved and carries
    therapeutic implications (e.g., anti-IL-17 blockade).
  evidence:
  - reference: PMID:35911678
    reference_title: "Gastric Th17 Cells Specific for H+/K+-ATPase and Serum IL-17 Signature in Gastric Autoimmunity."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Gastric LPMCs from all AIG patients, but not those from HCs, were activated by H+/K+-ATPase and were able to proliferate and produce high levels of IL-17A and IL-17F."
    explanation: Human gastric T cells produce IL-17A/IL-17F on H+/K+ ATPase stimulation, evidencing a Th17 effector contribution.
  - reference: PMID:18641328
    reference_title: "Th1, Th2, and Th17 effector T cell-induced autoimmune gastritis differs in pathological pattern and in susceptibility to suppression by regulatory T cells."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "We have evaluated the capacity of fully differentiated Th1, Th2, and Th17 cells derived from a mouse bearing a transgenic TCR specific for the gastric parietal cell antigen, H(+)K(+)-ATPase, to induce autoimmune gastritis after transfer to immunodeficient recipients."
    explanation: Th17 effector cells can independently induce autoimmune gastritis in the transfer model, supporting an emerging Th17 arm.
  - reference: PMID:31080562
    reference_title: "Intrinsic factor recognition promotes T helper 17/T helper 1 autoimmune gastric inflammation in patients with pernicious anemia."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Most of these clones (94%) showed a T helper 17 or T helper 1 profile."
    explanation: In pernicious anemia, intrinsic-factor-specific gastric CD4 clones are predominantly Th17/Th1 (Th17-skewed), evidencing a Th17 contribution in the intrinsic-factor-reactive compartment.
  - reference: PMID:40471463
    reference_title: "STAT3 inhibition mitigates experimental autoimmune gastritis by restoring Th17/Treg immune balance."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "STA-21 treatment alleviated gastric atrophy, reduced inflammatory infiltration, suppressed Th17 differentiation, and enhanced Treg function, reversing the Th17/Treg imbalance."
    explanation: STAT3 inhibition corrects the Th17/Treg imbalance and alleviates experimental autoimmune gastritis, implicating a STAT3-driven Th17/Treg axis rather than direct IL-17A/F epithelial cytotoxicity.
  notes: >-
    Two independent hypothesis-search runs concur on PARTIALLY SUPPORTED / retain
    EMERGING: a claude_code report
    (kb/hypotheses/Autoimmune_Gastritis/emerging_th17_effector_polarization/claude_code.md)
    and an openscientist report (same directory, openscientist.md). Both confirm a
    genuine Th17/IL-17 contribution (H+/K+ ATPase-specific gastric IL-17A/F
    production; 94% of intrinsic-factor-reactive clones Th17/Th1; Th17 transfer
    gives the most severe, Treg-resistant gastritis in the TxA23 model), but the
    openscientist run corrects the effector mechanism: IL-17RA signaling on gastric
    epithelium appears PROTECTIVE rather than directly apoptotic (IL-17RA loss
    increases B-cell infiltration, autoantibody production, and inflammation, and
    accelerates gastric carcinogenesis), so the pathogenic Th17-derived signal is
    more likely IL-21 and STAT3-mediated (STAT3 inhibition restores Th17/Treg
    balance and alleviates disease; PMID:40471463) than IL-17A/F epithelial
    cytotoxicity. Consequently anti-IL-17 blockade is cautioned/contraindicated
    (protective, anti-carcinogenic IL-17), no human anti-IL-17 AIG data exist, Th1
    remains the more extensively validated axis, and which arm dominates by disease
    stage is unresolved. Reframe: Th17 contributes via IL-21/STAT3, not direct
    IL-17A/F epithelial killing.
discussions:
- discussion_id: hmm_aig_mouse_model_neoplastic_trajectory
  prompt: >-
    Do murine autoimmune-gastritis models (neonatal thymectomy, H+/K+ ATPase
    immunization, and TCR-transgenic effector-transfer systems) faithfully
    reproduce human autoimmune gastritis, or do they capture only the initiation
    and parietal-cell-destruction biology while failing to model the
    human-specific downstream trajectory of chronic ECL-cell hyperplasia
    progressing to type 1 gastric neuroendocrine tumors, long-term gastric
    adenocarcinoma risk, and polyautoimmune clustering (thyroid, type 1 diabetes,
    vitiligo)?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump
  - pathophysiology#Hypergastrinemia and ECL Cell Hyperplasia
  rationale: >-
    Mouse models robustly recapitulate the core autoantigen (H+/K+ ATPase), the
    CD4 T-cell-mediated destructive mechanism, and atrophic/metaplastic histology,
    and they are the primary source of mechanistic detail (effector-subset
    pathogenicity and Treg-dependent tolerance). However, short-lived rodent
    models less consistently reproduce the chronic hypergastrinemia -> ECL
    hyperplasia -> type 1 gastric NET sequence and the decades-long adenocarcinoma
    risk that dominate human clinical management, and single-antigen mouse systems
    do not intrinsically model human polyautoimmune comorbidity. Consequently the
    neoplastic-complication arm of the human entry rests on human observational
    data rather than on validated model mechanism.
  proposed_experiments:
  - experiment_id: exp_aig_longterm_ecl_neoplasia
    name: Longitudinal ECL-to-NET progression in a chronic hypergastrinemic AIG model
    description: >-
      In a chronic autoimmune-gastritis model with sustained achlorhydria and
      hypergastrinemia, longitudinally quantify the ECL-cell
      hyperplasia -> dysplasia -> type 1 gastric NET sequence and adenocarcinoma
      incidence over extended timeframes, mapped onto human histologic staging.
    decision_criterion: >-
      Whether comparable degrees and durations of hypergastrinemia reproduce the
      human ECL-to-NET-to-adenocarcinoma sequence.
    would_support:
    - >-
      Faithful reproduction would validate the human neoplastic trajectory as a
      direct consequence of the modeled autoimmune-achlorhydria-hypergastrinemia
      axis.
    would_refute:
    - >-
      Failure to progress despite equivalent hypergastrinemia would indicate
      human-specific ECL/gastric-epithelial biology not captured by rodent models.
    model_systems:
    - name: Chronic murine autoimmune gastritis model
      description: >-
        Long-lived mouse model with sustained achlorhydria and hypergastrinemia
        (e.g., effector-transfer or gastrin-clamped systems) followed for ECL-cell
        neoplastic progression.
      experimental_model_type: OTHER
- discussion_id: gap_aig_sporadic_tolerance_trigger
  prompt: >-
    What initiates the loss of tolerance in the common sporadic (polygenic) form
    of autoimmune gastritis? H. pylori molecular mimicry is the leading trigger
    hypothesis, but established disease is usually H. pylori-negative and human
    causation is unproven; other triggers (viral, unidentified) and the
    gene-environment "second-hit" model (a PTPN22/HLA/AIRE background lowering the
    threshold for infection-triggered mimicry and epitope spreading) remain
    unvalidated in humans.
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump
  rationale: >-
    The trigger question directly gates the two competing origin hypotheses
    (primary autoimmunity vs. H. pylori mimicry) and determines whether a
    modifiable environmental exposure exists. It cannot be resolved by the current
    snippet-supported human associations, which are cross-sectional and
    confounded by the frequent absence of the organism at diagnosis.
- discussion_id: gap_aig_disease_modifying_therapy_active_window
  prompt: >-
    Is the autoimmune process still active and pharmacologically targetable at the
    time of diagnosis, or is it effectively "burnt out"? There is no
    disease-modifying therapy for autoimmune gastritis - management is
    micronutrient replacement and surveillance - and it is unknown whether early
    immunomodulation (regulatory T-cell restoration or Th17/IL-17 blockade) could
    halt progression to atrophy, pernicious anemia, and neoplasia.
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#CD4+ T Cell-Mediated Autoimmune Response Against the Gastric Proton Pump
  rationale: >-
    Whether the effector response persists at a targetable level once corpus
    atrophy is established determines if immunomodulatory therapy is even
    mechanistically plausible; the emerging Th17 arm makes anti-IL-17 blockade a
    concrete but untested candidate.
- discussion_id: gap_aig_natural_history_pediatric
  prompt: >-
    What is the natural history and timeline of autoimmune gastritis from the
    earliest seropositive ("potential AIG") phase through corpus atrophy,
    pernicious anemia, and neoplastic complications, and what distinguishes the
    poorly-studied pediatric-onset subgroup?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Parietal Cell Destruction and Oxyntic Atrophy
  rationale: >-
    The pre-atrophic seropositive phase is the clinically actionable window for
    early detection, but the rate and determinants of progression to irreversible
    atrophy and to neoplasia are not established prospectively, and the
    pediatric-onset subgroup's long-term course is largely unstudied.

📚

References & Deep Research

References

7

PMID:42367768

Autoimmune gastritis: a comprehensive review of pathophysiology, risk stratification, and management.