Definition/General
Introduction:
Eosinophilic gastritis is a rare inflammatory disorder characterized by eosinophilic infiltration of the gastric wall
It is part of eosinophilic gastroenteritis spectrum
It involves allergic hypersensitivity mechanisms
It can affect any layer of the gastric wall.
Origin:
Results from type I hypersensitivity reaction to food allergens or environmental triggers
Involves IgE-mediated and non-IgE-mediated mechanisms
Th2-mediated immune response predominates
Releases eosinophil-derived mediators
Causes tissue damage and inflammation.
Classification:
Classified by predominant layer involvement: mucosal type (most common, 90%)
Muscular type (gastric outlet obstruction)
Serosal type (eosinophilic ascites)
Mixed patterns possible
Part of eosinophilic gastroenteritis spectrum.
Epidemiology:
Rare condition (<1% of gastritis cases)
Male predominance (2:1 ratio)
Bimodal age distribution: children and young adults
Associated with atopic conditions (40-50% cases)
Family clustering reported
Higher in developed countries.
Clinical Features
Presentation:
Epigastric pain (most common)
Nausea and vomiting
Food allergies and intolerances
Early satiety and bloating
Gastric outlet obstruction (muscular involvement)
Iron deficiency anemia (mucosal ulceration).
Symptoms:
Abdominal pain (postprandial)
Dyspepsia and indigestion
Nausea and vomiting
Diarrhea (if small bowel involved)
Weight loss
Allergic symptoms: rash, asthma, rhinitis
Protein-losing enteropathy (severe cases).
Risk Factors:
Food allergies (milk, eggs, seafood, nuts)
Atopic conditions: asthma, eczema, allergic rhinitis
Family history of allergies
Environmental allergens
Drug hypersensitivity
Parasitic infections (differential diagnosis).
Screening:
Peripheral eosinophilia (>4% or >450 cells/μL)
Elevated IgE levels
Food-specific IgE testing
Stool examination (parasites)
Upper endoscopy with biopsy
CT scan (muscular/serosal involvement).
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Gross Description
Appearance:
Mucosal erythema and edema
Nodular gastritis pattern
Mucosal thickening and rigidity
Ulcerations may be present
Pyloric stenosis (muscular involvement)
Normal appearance possible (early disease).
Characteristics:
Antral involvement most common
Diffuse mucosal changes
Cobblestone appearance
Loss of normal fold pattern
Thickened gastric wall (muscular type)
Luminal narrowing possible.
Size Location:
Antral predominance (60-70% cases)
May involve entire stomach
Pyloric involvement common
Concurrent duodenal involvement
Segmental distribution possible.
Multifocality:
Patchy distribution initially
May become diffuse over time
Often part of eosinophilic gastroenteritis
Concurrent small bowel involvement
Skip lesions possible.
Microscopic Description
Histological Features:
Marked eosinophilic infiltration (>30 eosinophils/hpf)
Involves lamina propria predominantly
Chronic inflammation with lymphocytes and plasma cells
Surface epithelial damage
Crypt architectural distortion.
Cellular Characteristics:
Dense eosinophilic infiltrate
Degranulating eosinophils
Tissue eosinophilia
Charcot-Leyden crystals
Mixed inflammatory infiltrate
Increased mast cells
Epithelial damage and regeneration.
Architectural Patterns:
Mucosal thickening
Crypt elongation and distortion
Surface epithelial erosions
Lamina propria expansion
Muscular layer involvement (muscular type)
Submucosal fibrosis (chronic cases).
Grading Criteria:
Eosinophil count: >30/hpf (mucosal)
>50/hpf (diagnostic threshold)
Distribution assessment: mucosal, muscular, serosal
Architectural changes: mild, moderate, severe
Associated tissue damage evaluation.
Immunohistochemistry
Positive Markers:
CD68 (increased macrophages)
Tryptase (increased mast cells)
CD117 (mast cells)
Ki-67 (increased proliferation)
IgE (tissue deposition)
CD20 (B-cell component).
Negative Markers:
CD30 (excludes lymphoma)
ALK (excludes inflammatory myofibroblastic tumor)
CD117 in spindle cells (excludes GIST)
Parasitic organisms (special stains negative).
Diagnostic Utility:
Confirms eosinophilic nature of infiltrate
Excludes parasitic infection
Identifies mast cell involvement
Assesses tissue IgE deposition
Rules out malignancy
Evaluates inflammatory response.
Molecular Subtypes:
IgE-mediated type: immediate hypersensitivity
Non-IgE-mediated: delayed hypersensitivity
Mixed pattern
Th2-driven inflammation
IL-5 and IL-13 mediated eosinophil recruitment.
Molecular/Genetic
Genetic Mutations:
STAT6 gene variants
IL-13 gene polymorphisms
IL-5 receptor variants
Eotaxin gene polymorphisms
FIP1L1-PDGFRA fusion (hypereosinophilic syndrome)
TPSAB1 gene variants.
Molecular Markers:
Elevated IL-5 and IL-13
Increased eotaxin levels
IgE elevation
Tryptase levels
Eosinophil cationic protein
Th2 cytokine profile.
Prognostic Significance:
Mucosal type: better prognosis
Muscular type: risk of obstruction
Serosal type: risk of ascites
Response to treatment: varies by subtype
Chronic fibrosis: poor outcome.
Therapeutic Targets:
Corticosteroids: first-line therapy
Elimination diet: food allergen identification
Antihistamines
Mast cell stabilizers
Anti-IL-5 therapy: mepolizumab
Leukotriene receptor antagonists.
Differential Diagnosis
Similar Entities:
Parasitic gastritis (Anisakis, Strongyloides)
Drug-induced eosinophilia
Hypereosinophilic syndrome
Inflammatory myofibroblastic tumor
GIST with eosinophilia
Crohn disease.
Distinguishing Features:
Eosinophilic gastritis: tissue eosinophilia >30/hpf, food allergies
Parasitic: organisms identified, travel history
Drug-induced: temporal relationship
HES: systemic eosinophilia >1500/μL
IMT: spindle cells, ALK+.
Diagnostic Challenges:
Establishing eosinophil threshold
Identifying underlying triggers
Distinguishing from secondary eosinophilia
Correlating with clinical symptoms
Excluding parasitic infections
Assessing extent of involvement.
Rare Variants:
Eosinophilic ascites (serosal type)
Gastric perforation
Massive gastric wall thickening
Concurrent eosinophilic esophagitis
Protein-losing gastropathy.
Sample Pathology Report
Template Format
Sample Pathology Report
Complete Report: This is an example of how the final pathology report should be structured for this condition.
Specimen Information
Gastric biopsy from [site], [number] fragments
Diagnosis
Eosinophilic gastritis
Eosinophil Count
Eosinophils: [number]/hpf (normal <20/hpf)
Distribution
Predominant involvement: [mucosal/muscular/serosal]
Histological Features
Dense eosinophilic infiltrate with chronic inflammation and epithelial damage
Parasites
No parasitic organisms identified
Special Studies
Tryptase: [result], CD68: [result]
Peripheral eosinophilia: [present/absent]
[other study]: [result]
Recommendations
Clinical correlation, allergy testing, consider elimination diet
Final Diagnosis
Eosinophilic gastritis with [degree] eosinophilic infiltration