Allergic disorders - sinusitis
Description
- Allergic rhinitis with sinus involvement and chronic rhinosinusitis (CRS) driven or worsened by allergic inflammation
- Distinguish from acute bacterial sinusitis (a separate, infective, self-limiting problem) - allergic disease is chronic and inflammatory, not infective at its core
Epidemiology
- Allergic rhinitis affects ~15-20% of the population; a large proportion have concurrent sinus mucosal disease
- CRS with nasal polyps often has a Type 2/eosinophilic allergic-adjacent phenotype, frequently associated with asthma and aspirin-exacerbated respiratory disease (AERD)
Aetiopathogenesis
- IgE-mediated Type I hypersensitivity to inhalant allergens (house dust mite, pollen, mould, animal dander) -> mast cell degranulation -> mucosal oedema, hypersecretion, ciliary dysfunction
- Chronic mucosal oedema -> ostiomeatal complex obstruction -> impaired sinus drainage/aeration -> secondary bacterial superinfection risk and polyp formation
- Samter's triad (AERD) - asthma + nasal polyps + aspirin/NSAID sensitivity - due to dysregulated arachidonic acid metabolism (leukotriene overproduction), not IgE-mediated
Diagnosis
Clinical
- Nasal congestion, clear rhinorrhoea, sneezing, itch (nose/eyes/palate), facial pressure, anosmia/hyposmia
- Allergic rhinitis features: seasonal or perennial pattern, allergic "shiners", nasal crease, pale/boggy turbinates on exam
- CRS diagnostic criteria: >=2 of (nasal blockage, discharge, facial pain/pressure, reduced smell) for >=12 weeks, plus objective evidence (endoscopy or CT)
Investigations
- Allergy testing (skin prick or specific IgE) to confirm/identify triggers if allergen avoidance or immunotherapy being considered
- Nasal endoscopy - polyps, mucosal oedema, purulent discharge
- CT sinuses - if surgery being considered, or diagnosis unclear (not for routine allergic rhinitis)
Management
By presenting problem
### Allergic rhinitis (with/without sinus involvement)
- Intranasal corticosteroid - most effective single therapy, first-line for moderate-severe/persistent symptoms
- Non-sedating oral antihistamine - for itch/sneeze-predominant symptoms, adjunct to intranasal steroid
- Intranasal antihistamine or combination intranasal antihistamine-steroid spray - faster onset, useful for intermittent/breakthrough symptoms
- Saline irrigation - adjunct, improves mucociliary clearance
- Allergen avoidance where a specific trigger is identified
- Allergen immunotherapy (SCIT/SLIT) - for confirmed IgE-mediated disease refractory to medical therapy, or to modify long-term course
### Chronic rhinosinusitis with nasal polyps
- Intranasal corticosteroid (drops or high-volume rinse for polyps), saline irrigation
- Short course oral corticosteroid for significant polyp burden/exacerbation
- Biologics (dupilumab, mepolizumab, omalizumab) for severe refractory CRSwNP, especially with comorbid asthma/AERD
- Endoscopic sinus surgery if medical therapy fails
### AERD specifically
- Strict aspirin/NSAID avoidance unless desensitised; aspirin desensitisation can improve polyp/asthma control in selected patients
- Leukotriene receptor antagonists as adjunct given the leukotriene-driven pathophysiology
Associations
- Asthma - "one airway" concept, poorly controlled rhinosinusitis worsens asthma control
- Nasal polyps, AERD
- Otitis media with effusion (esp. children), obstructive sleep symptoms
- Secondary acute bacterial sinusitis
Natural history & complications
- Allergic rhinitis often persists for years, may improve or change allergen sensitisation pattern over time
- CRS with nasal polyps - relapsing course, frequently recurs after surgery without ongoing medical therapy
- Biologic therapy has changed the trajectory for severe CRSwNP/AERD patients previously facing repeated sinus surgery
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