Eosinophilic Granuloma of Paranasal Sinuses

1) Definition and Terminology

1. Eosinophilic chronic rhinosinusitis (ECRS) with polypoidal disease
2. Allergic fungal rhinosinusitis (AFRS) and eosinophilic mucin disorders
3. Less commonly, true Langerhans cell histiocytosis (LCH) eosinophilic granuloma involving sinonasal bones

2) Etiopathogenesis (Core concept)

A. Immunopathology (Type-2 inflammation)

• Epithelial barrier dysfunction (pollutants, microbes, allergens)
• Release of alarmins: TSLP, IL-25, IL-33
• Activation of Th2 cells and ILC2
• Cytokines: IL-4, IL-5, IL-13
• Recruitment/activation of eosinophils
• Eosinophil degranulation (ECP, MBP) causes mucosal edema, polyp formation, persistent inflammation

Flowchart 1: Pathogenesis

Trigger (allergen/fungi/microbe/irritant)
          ↓
Epithelial injury + alarmins (TSLP, IL-25, IL-33)
          ↓
Th2/ILC2 polarization
          ↓
IL-4, IL-5, IL-13 ↑
          ↓
Eosinophil recruitment + IgE amplification
          ↓
Mucosal edema + thick eosinophilic mucin + polyps
          ↓
Ostial obstruction + sinus stasis
          ↓
Recurrent/chronic disease

B. Role of fungi and superantigens

• In AFRS: hypersensitivity to fungal antigens with eosinophilic mucin
• Staphylococcal superantigens may amplify local IgE and eosinophilic inflammation

C. Remodeling

• Basement membrane thickening, edema, pseudocyst formation
• Higher recurrence tendency after surgery if inflammation is uncontrolled

3) Epidemiology and Risk Factors

• Young to middle-aged adults (often)
• Strong association with:
  • Bronchial asthma
  • Aspirin/NSAID-exacerbated respiratory disease (AERD)
  • Atopy
  • Recurrent nasal polyposis
• Peripheral blood eosinophilia may be present (not universal)

4) Clinical Features

Symptoms

• Nasal obstruction (usually bilateral)
• Rhinorrhea, often thick/mucoid
• Postnasal drip
• Hyposmia/anosmia
• Facial pressure/fullness
• Headache
• Recurrent acute exacerbations

Signs (DNE/endoscopy)

• Pale, edematous mucosa
• Multiple polyps (middle meatus predominant)
• Thick tenacious eosinophilic mucin (“peanut butter” consistency in AFRS)
• Possible mucopus in secondary infection

Advanced/complicated disease

• Proptosis, facial asymmetry (sinus expansion in AFRS)
• Rare orbital/intracranial extension from pressure erosion or secondary infection

5) Investigations

A. Nasal endoscopy

• Extent of polyposis
• Mucin character
• Site-directed sampling for fungal stain/culture and histopathology

B. Imaging

CT PNS (non-contrast) is primary

• Sinonasal opacification, polyposis
• Hyperdense areas within sinus content (allergic mucin/fungal debris)
• Expansion/remodeling, thinning/erosion of bony walls (especially in AFRS)

MRI (selected)

• Better soft tissue distinction
• Helps exclude neoplasm/orbital/intracranial complications

Diagram (text): Typical CT pattern in eosinophilic fungal disease

[Ethmoid + Maxillary + Frontal opacification]
      with
[Central hyperattenuating foci]
      with
[Sinus expansion/remodeling ± bone thinning]

C. Laboratory and pathology

• CBC: eosinophilia (supportive)
• Total serum IgE often elevated (especially AFRS)
• Specific IgE/skin tests for allergens/fungi
• Histopathology:
  • Dense eosinophilic infiltrate
  • Charcot-Leyden crystals may be seen
  • Allergic mucin; fungal hyphae on special stains in AFRS
• Tissue biopsy when atypical/unilateral/aggressive to rule out neoplasm, vasculitis, invasive fungal disease, LCH

6) Diagnostic Approach (Exam-friendly algorithm)

Chronic rhinosinusitis symptoms >12 weeks
        ↓
Nasal endoscopy + CT PNS
        ↓
Eosinophilic phenotype suspected?
(polyps, thick mucin, asthma/AERD, eosinophilia)
        ↓
Phenotype/endotype workup:
CBC eosinophils, IgE, allergy tests, pathology of mucin/tissue
        ↓
Classify:
ECRS / AFRS / other CRS phenotype / alternate diagnosis
        ↓
Plan:
Medical optimization ± ESS ± long-term anti-inflammatory control

7) Differential Diagnosis

• Non-eosinophilic CRS with polyps
• Invasive fungal sinusitis
• Sinonasal neoplasm
• Granulomatous disease (GPA, sarcoid, TB)
• Sinonasal LCH eosinophilic granuloma (rare)
• Mucocele, antrochoanal polyp, odontogenic sinus disease

8) Management

A. Medical treatment

1. Intranasal corticosteroids (first-line long-term)
2. Saline irrigation (high-volume preferred post-op)
3. Short oral steroid course for severe polyp burden/exacerbation
4. Antibiotics only when bacterial infection is evident
5. Leukotriene modifiers (selected cases, especially AERD/asthma overlap)
6. Allergy-directed management: allergen avoidance, selected immunotherapy in suitable atopic patients
7. Antifungals: routine systemic antifungals not universally recommended in non-invasive eosinophilic disease; use is selective and guideline-dependent

B. Surgical management

Functional Endoscopic Sinus Surgery (FESS/ESS)

• Failure of maximal medical therapy
• Heavy polyp/mucin burden
• Obstructed sinus ventilation/drainage
• Complications (orbital/intracranial risk, severe expansion)

• Complete clearance of polyps and allergic mucin
• Wide marsupialization/opening of involved sinuses
• Preserve mucosa where possible
• Create access for long-term topical therapy

Flowchart 2: Treatment pathway

Diagnosed eosinophilic sinonasal disease
        ↓
Maximal medical therapy (steroid spray + saline ± short oral steroid)
        ↓
Adequate control?
   ├── Yes → Maintenance + periodic endoscopic follow-up
   └── No  → ESS
                ↓
Post-op protocol:
debridement + steroid irrigations + control of asthma/AERD/allergy
                ↓
Recurrence?
   ├── No → continue maintenance
   └── Yes → optimize medical therapy ± revision ESS ± biologic therapy

9) Recent Advances (high-yield)

A. Endotype-based care

• Blood eosinophils
• Total IgE
• Clinical comorbidities (asthma, AERD)
• Tissue eosinophilia where available

B. Biologic therapies (for severe, recurrent type-2 CRSwNP)

• Dupilumab (anti-IL-4Rα; blocks IL-4/IL-13 signaling)
• Mepolizumab / Reslizumab (anti-IL-5 pathway)
• Benralizumab (anti-IL-5Rα)
• Omalizumab (anti-IgE)

• Reduced polyp size
• Better nasal obstruction and smell
• Less need for systemic steroids/surgery
• Improved quality of life

C. Enhanced topical delivery

• Steroid irrigations/nebulized strategies after wide ESS improve local control vs spray alone in extensive disease

D. Recurrence prediction and precision follow-up

• Tissue eosinophil thresholds, blood eosinophils, and comorbidity profiling help predict relapse and tailor follow-up intensity

10) Complications

• Recurrent polyposis (most common long-term issue)
• Chronic anosmia/hyposmia
• Recurrent sinus infections
• Rare: orbital/intracranial complications due to advanced disease or secondary infection
• Steroid-related adverse effects (if repeated systemic use)

11) Prognosis

• Good symptom control is achievable with proper surgery + long-term anti-inflammatory maintenance
• Recurrence is common in high eosinophilic burden, asthma, AERD, and inadequate postoperative topical control
• Long-term follow-up is essential

12) If examiner asks specifically: “Eosinophilic granuloma = LCH of sinonasal region”

• Clonal Langerhans cell disorder, rare in paranasal region
• Symptoms: obstruction, pain, swelling, epistaxis; possible bony destruction
• Diagnosis: biopsy with CD1a/Langerin(S100)+ cells
• Management: lesion-directed surgery/curettage ± steroids/oncology protocols depending on extent
• Different entity from eosinophilic CRS/AFRS

13) Suggested “diagram page” for exam

1. Pathogenesis flowchart (already given)
2. CT schematic showing opacified sinuses with central hyperdense areas and sinus expansion
3. Management algorithm from medical therapy to ESS to biologics/revision

14) Key textbook-aligned takeaways

• Scott-Brown/Cummings/Stell-Marans style emphasis: classify CRS phenotype, endoscopic and radiologic mapping, surgery plus long-term medical maintenance
• Dhingra/Hazarika style exam emphasis: definitions, diagnostic criteria, FESS principles, postoperative care, recurrence prevention
• Current literature emphasis: type-2 inflammation, biologics, and precision long-term care