Definition/General
Introduction:
Eosinophilic colitis is inflammatory condition characterized by increased eosinophils in colonic mucosa
Part of eosinophilic gastrointestinal disorders spectrum
Shows allergic or hypersensitivity mechanism
Variable clinical presentation from mild symptoms to severe colitis.
Origin:
Results from allergic hypersensitivity to food antigens or medications
Shows Th2-mediated immune response
Demonstrates eosinophil degranulation and tissue damage
Associated with atopic conditions
IgE-mediated or non-IgE mechanisms.
Classification:
Primary eosinophilic colitis (isolated colonic involvement)
Eosinophilic gastroenteritis (multi-organ involvement)
Drug-induced eosinophilic colitis
Parasitic-associated
Hypereosinophilic syndrome with GI involvement.
Epidemiology:
Peak incidence in children and young adults
Male predominance (pediatric)
Associated with atopic diseases
Food allergies common trigger
Increasing recognition with better awareness
Rare condition overall.
Clinical Features
Presentation:
Chronic diarrhea (most common)
Abdominal pain
Rectal bleeding (variable)
Food intolerance
Failure to thrive (children)
Peripheral eosinophilia (50-80% cases).
Symptoms:
Crampy abdominal pain
Loose stools with mucus
Nausea and vomiting
Weight loss
Bloating
Food-related symptoms.
Risk Factors:
Atopic diseases (asthma, eczema)
Food allergies
Family history of atopy
Environmental allergens
Drug hypersensitivity
Parasitic infections.
Screening:
Complete blood count (eosinophilia)
IgE levels
Food-specific IgE
Colonoscopy with biopsy
Stool examination (parasites)
Allergy testing.
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Gross Description
Appearance:
Variable endoscopic findings
Mucosal erythema and edema
Nodular mucosa
Ulceration (severe cases)
Polypoid lesions
Normal appearance (mild cases).
Characteristics:
Patchy mucosal changes
Friable mucosa
Thickened bowel wall
Pseudopolyps
Cobblestone appearance
Multiple small ulcers.
Size Location:
Right-sided predominance (cecum, ascending colon)
Pan-colonic involvement (severe cases)
Segmental involvement
Rectosigmoid (variable)
Terminal ileum involvement possible.
Multifocality:
Patchy distribution
Skip lesions
Variable severity
Waxing and waning course
Food trigger correlation.
Microscopic Description
Histological Features:
Marked eosinophilic infiltration (>50 eosinophils per HPF)
Eosinophil degranulation
Cryptitis with eosinophils
Surface epithelial damage
Chronic inflammation
Edema.
Cellular Characteristics:
Mature eosinophils in lamina propria
Intraepithelial eosinophils
Eosinophil degranulation (Charcot-Leyden crystals)
Lymphocytes and plasma cells
Mast cell infiltration.
Architectural Patterns:
Preserved crypt architecture (early)
Crypt distortion (chronic)
Surface ulceration
Villous blunting
Submucosal eosinophilia
Muscular layer involvement (severe).
Grading Criteria:
Mild: >50 eosinophils/HPF, minimal tissue damage
Moderate: >100 eosinophils/HPF, crypt distortion
Severe: >200 eosinophils/HPF, ulceration, architectural distortion.
Immunohistochemistry
Positive Markers:
Major basic protein (eosinophil granules)
Eosinophil cationic protein
CD68 (macrophages)
Mast cell tryptase
IgE (plasma cells).
Negative Markers:
Parasitic antigens (unless parasitic cause)
Malignancy markers
Specific infectious agents
IBD-specific markers.
Diagnostic Utility:
Highlights eosinophil products
Confirms eosinophil degranulation
Excludes other causes
Usually morphology sufficient
Research applications.
Molecular Subtypes:
Food allergy-mediated
Drug-induced
Atopic dermatitis-associated
Hypereosinophilic syndrome
Idiopathic.
Molecular/Genetic
Genetic Mutations:
No specific mutations
Atopy susceptibility genes
IL-5 pathway genes
Th2 immune response genes
FIP1L1-PDGFRA (hypereosinophilic syndrome).
Molecular Markers:
IL-5 (eosinophil activation)
IL-13 (Th2 response)
Eotaxin (eosinophil chemotaxis)
IgE (allergic response)
Eosinophil granule proteins.
Prognostic Significance:
Trigger identification improves prognosis
Dietary elimination response
Steroid responsiveness
Chronic relapsing course
No malignant potential.
Therapeutic Targets:
Dietary elimination (food triggers)
Corticosteroids
Antihistamines
Mast cell stabilizers
Anti-IL-5 therapy (severe cases).
Differential Diagnosis
Similar Entities:
Parasitic infections (strongyloidiasis, hookworm)
Drug-induced colitis
Inflammatory bowel disease
Hypereosinophilic syndrome
Allergic proctocolitis (infants)
Mastocytic enterocolitis.
Distinguishing Features:
Eosinophilic colitis: Marked eosinophilia, food triggers, atopic history
Parasitic: Organisms identified, travel history
Drug-induced: Medication history
IBD: Architectural distortion, chronic changes
HES: Multi-organ involvement, blood eosinophilia.
Diagnostic Challenges:
Distinguishing from parasitic infections (stool examination crucial)
Identifying food triggers
Differentiating from IBD with eosinophilia
Recognizing drug-induced cases
Quantifying eosinophils accurately.
Rare Variants:
Eosinophilic proctocolitis (infants)
Protein-induced enterocolitis syndrome
Allergic proctitis
Eosinophilic ascites
Systemic mastocytosis with GI involvement.
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
[specimen type] from [anatomical location]
Clinical Information
Chronic diarrhea. Food allergies: [yes/no]. Atopic diseases: [specify]. Peripheral eosinophilia: [present/absent]
Eosinophil Quantification
Eosinophils: [X] per high power field (normal <5-10 per HPF, diagnostic >50 per HPF)
Distribution Pattern
Eosinophil distribution: [mucosal/submucosal/transmural]. Degranulation: [present/absent]
Inflammatory Features
Surface epithelial damage: [present/absent]. Cryptitis: [present/absent]. Chronic inflammation: [mild/moderate/severe]
Parasite Exclusion
No parasitic organisms identified. Stool examination recommended for confirmation.
Architecture Assessment
Crypt architecture: [preserved/distorted]. Surface changes: [present/absent]
Recommendations
Allergy evaluation recommended. Food elimination trial may be beneficial. Stool parasite examination advised.
Final Diagnosis
Eosinophilic Colitis - [Primary/Secondary to food allergy/Drug-induced]